View source for Zoonosis

{{Short description|Diseases of humans caused by a pathogen}}
{{Redirect|Zoonotic|the television episode|Zoonotic (Law & Order: Criminal Intent){{!}}Zoonotic (''Law & Order: Criminal Intent'')}}
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A '''zoonosis''' ({{IPAc-en|z|oʊ|ˈ|ɒ|n|ə|s|ɪ|s|,_|ˌ|z|oʊ|ə|ˈ|n|oʊ|s|ɪ|s|audio=LL-Q1860 (eng)-Wodencafe-zoonosis.wav}};<ref name="mw">{{cite Merriam-Webster|zoonosis|access-date=29 March 2019}}</ref> plural '''zoonoses''') or '''zoonotic disease''' is an [[infectious disease]] of humans caused by a [[pathogen]] (an infectious agent, such as a [[virus]], [[bacterium]], [[parasite]], [[Fungus|fungi]], or [[prion]]) that can [[Cross-species transmission|jump]] from a non-human [[vertebrate]] to a [[human]]. When humans infect non-humans, it is called [[reverse zoonosis]] or anthroponosis.<ref>{{cite journal |vauthors=Messenger AM, Barnes AN, Gray GC |date=2014 |title=Reverse zoonotic disease transmission (zooanthroponosis): a systematic review of seldom-documented human biological threats to animals |journal=PLOS ONE |volume=9 |issue=2 |article-number=e89055 |bibcode=2014PLoSO...989055M |doi=10.1371/journal.pone.0089055 |pmc=3938448 |pmid=24586500 |doi-access=free}}</ref><ref name="mw"/><ref>{{cite web|last1=WHO|title=Zoonoses|url=https://www.who.int/topics/zoonoses/en/|access-date=18 December 2014|archive-url=https://web.archive.org/web/20150103010751/http://www.who.int/topics/zoonoses/en/|archive-date=3 January 2015|url-status=live}}</ref><ref name="sgc">{{cite web |title=A glimpse into Canada's highest containment laboratory for animal health: The National Centre for Foreign Animal Diseases |url=http://www.science.gc.ca/eic/site/063.nsf/eng/97704.html |website=science.gc.ca |publisher=Government of Canada |date=22 October 2018 |quote=Zoonoses are infectious diseases which jump from a non-human host or reservoir into humans. |access-date=16 August 2019 |archive-url=https://web.archive.org/web/20190620024804/http://science.gc.ca/eic/site/063.nsf/eng/97704.html |archive-date=20 June 2019 |url-status=live }}</ref>

Major modern diseases such as [[Ebola]] and [[salmonellosis]] are zoonoses. [[HIV]] was a zoonotic disease transmitted to humans in the early part of the 20th century, though it has now evolved into a separate human-only disease.<ref name="Orgin2011">{{cite journal | vauthors = Sharp PM, Hahn BH | title = Origins of HIV and the AIDS pandemic | journal = Cold Spring Harbor Perspectives in Medicine | volume = 1 | issue = 1 | article-number = a006841 | date = September 2011 | pmid = 22229120 | pmc = 3234451 | doi = 10.1101/cshperspect.a006841 }}</ref><ref name="Faria2014">{{cite journal | vauthors = Faria NR, Rambaut A, Suchard MA, Baele G, Bedford T, Ward MJ, Tatem AJ, Sousa JD, Arinaminpathy N, Pépin J, Posada D, Peeters M, Pybus OG, Lemey P | display-authors = 6 | title = HIV epidemiology. The early spread and epidemic ignition of HIV-1 in human populations | journal = Science | volume = 346 | issue = 6205 | pages = 56–61 | date = October 2014 | pmid = 25278604 | pmc = 4254776 | doi = 10.1126/science.1256739 | bibcode = 2014Sci...346...56F }}</ref><ref name="Marx2001">{{cite journal | vauthors = Marx PA, Alcabes PG, Drucker E | title = Serial human passage of simian immunodeficiency virus by unsterile injections and the emergence of epidemic human immunodeficiency virus in Africa | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 356 | issue = 1410 | pages = 911–920 | date = June 2001 | pmid = 11405938 | pmc = 1088484 | doi = 10.1098/rstb.2001.0867 }}</ref> Human infection with animal [[influenza]] viruses is rare, as they do not transmit easily to or among humans.<ref>{{Cite web |last=World Health Organization |date=3 October 2023 |title=Influenza (Avian and other zoonotic) |url=https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic) |access-date=6 April 2024 |website=who.int}}</ref> However, [[Avian influenza|avian]] and [[swine influenza]] viruses in particular possess high zoonotic potential,<ref>{{Cite journal |last1=Abdelwhab |first1=EM |last2=Mettenleiter |first2=TC |date=April 2023 |title=Zoonotic Animal Influenza Virus and Potential Mixing Vessel Hosts |journal=Viruses |volume=15 |issue=4 |page=980 |doi=10.3390/v15040980 |doi-access=free |pmc=10145017 |pmid=37112960}}</ref> and these occasionally recombine with human strains of the flu and can cause [[pandemic]]s such as the [[2009 swine flu pandemic|2009 swine flu]].<ref>{{cite journal | vauthors = Scotch M, Brownstein JS, Vegso S, Galusha D, Rabinowitz P | title = Human vs. animal outbreaks of the 2009 swine-origin H1N1 influenza A epidemic | journal = EcoHealth | volume = 8 | issue = 3 | pages = 376–380 | date = September 2011 | pmid = 21912985 | pmc = 3246131 | doi = 10.1007/s10393-011-0706-x }}</ref> Zoonoses can be caused by a range of disease pathogens such as [[emergent virus]]es, bacteria, fungi and parasites; of 1,415 pathogens known to infect humans, 61% were zoonotic.<ref>{{cite journal | vauthors = Taylor LH, Latham SM, Woolhouse ME | title = Risk factors for human disease emergence | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 356 | issue = 1411 | pages = 983–989 | date = July 2001 | pmid = 11516376 | pmc = 1088493 | doi = 10.1098/rstb.2001.0888 }}</ref> Most human diseases originated in non-humans; however, only diseases that routinely involve non-human to human transmission, such as [[rabies]], are considered direct zoonoses.<ref>{{cite journal | vauthors = Marx PA, Apetrei C, Drucker E | title = AIDS as a zoonosis? Confusion over the origin of the virus and the origin of the epidemics | journal = Journal of Medical Primatology | volume = 33 | issue = 5–6 | pages = 220–226 | date = October 2004 | pmid = 15525322 | doi = 10.1111/j.1600-0684.2004.00078.x | doi-access = free }}</ref>

Zoonoses have different modes of transmission. In direct zoonosis the disease is directly transmitted between non-humans and humans through the air (influenza), bites and saliva (rabies),<ref>{{cite web |url=http://www.theodora.com/medical_dictionary/zonal_zoster.html#zoonosis |title=Zoonosis |work=Medical Dictionary |access-date=30 January 2013 |archive-url=https://web.archive.org/web/20130628092144/http://www.theodora.com/medical_dictionary/zonal_zoster.html#zoonosis |archive-date=28 June 2013 |url-status=live }}</ref> faecal-oral transmission or through contaminated food. Transmission can also occur via an intermediate species (referred to as a [[Vector (epidemiology)|vector]]), which carry the disease pathogen without getting sick. The term is {{Etymology|grc|''ζῷον'' (zoon)|animal||''νόσος'' (nosos)|sickness}}.

Host genetics plays an important role in determining which non-human viruses will be able to make copies of themselves in the human body. Dangerous non-human viruses are those that require few mutations to begin replicating themselves in human cells. These viruses are dangerous since the required combinations of mutations might randomly arise in the [[natural reservoir]].<ref>{{cite journal | vauthors = Warren CJ, Sawyer SL | title = How host genetics dictates successful viral zoonosis | journal = PLOS Biology | volume = 17 | issue = 4 | article-number = e3000217 | date = April 2019 | pmid = 31002666 | pmc = 6474636 | doi = 10.1371/journal.pbio.3000217 | author2-link = Sara Sawyer | doi-access = free }}</ref>

== Causes ==
The emergence of zoonotic diseases originated with the [[domestication]] of animals.<ref>{{cite book | vauthors = Nibert D |author-link=David Nibert |date=2013 |title=Animal Oppression and Human Violence: Domesecration, Capitalism, and Global Conflict |location= |publisher=[[Columbia University Press]] |page=5 |isbn=978-0-231-15189-4}}</ref><ref name=":3">{{Cite journal |last1=Salinas-Ramos |first1=Valeria B. |last2=Mori |first2=Emiliano |last3=Bosso |first3=Luciano |last4=Ancillotto |first4=Leonardo |last5=Russo |first5=Danilo |date=2021-03-05 |title=Zoonotic Risk: One More Good Reason Why Cats Should Be Kept Away from Bats |journal=Pathogens |language=en |volume=10 |issue=3 |page=304 |doi=10.3390/pathogens10030304 |doi-access=free |issn=2076-0817 |pmc=8002059 |pmid=33807760}}</ref> Zoonotic transmission can occur in any context in which there is contact with or consumption of animals, animal products, or animal derivatives. This can occur in a companionistic (pets),<ref name=":3" /> economic (farming, trade, butchering, etc.), predatory (hunting, butchering, or consuming wild game), or research context.<ref>{{Cite web |last=CDC |date=2024-05-16 |title=About Zoonotic Diseases |url=https://www.cdc.gov/one-health/about/about-zoonotic-diseases.html |access-date=2025-02-10 |website=One Health |language=en-us}}</ref><ref>{{Cite web |title=Zoonoses |url=https://www.who.int/news-room/fact-sheets/detail/zoonoses |access-date=2025-02-10 |website=www.who.int |language=en}}</ref>

Recently, there has been a rise in frequency of appearance of new zoonotic diseases. "Approximately 1.67 million undescribed viruses are thought to exist in [[mammal]]s and birds, up to half of which are estimated to have the potential to spill over into humans", says a study<ref>{{cite journal | vauthors = Grange ZL, Goldstein T, Johnson CK, Anthony S, Gilardi K, Daszak P, Olival KJ, O'Rourke T, Murray S, Olson SH, Togami E, Vidal G, Mazet JA | display-authors = 6 | title = Ranking the risk of animal-to-human spillover for newly discovered viruses | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 118 | issue = 15 | date = April 2021 | article-number = e2002324118 | pmid = 33822740 | pmc = 8053939 | doi = 10.1073/pnas.2002324118 | bibcode = 2021PNAS..11802324G | doi-access = free }}</ref> led by researchers at the [[University of California, Davis]]. According to a report from the [[United Nations Environment Programme]] and [[International Livestock Research Institute]] a large part of the causes are environmental like [[climate change]], unsustainable agriculture, exploitation of wildlife, and [[land use change]]. Others are linked to changes in human society such as an increase in mobility. The organizations propose a set of measures to stop the rise.<ref name="bbc.com">{{cite news |title=Coronavirus: Fear over rise in animal-to-human diseases |url=https://www.bbc.com/news/health-53314432 |access-date=7 July 2020 |agency=BBC |date=6 July 2020 |archive-date=7 July 2020 |archive-url=https://web.archive.org/web/20200707015347/https://www.bbc.com/news/health-53314432 |url-status=live }}</ref><ref name="United Nations">{{cite web |title=Preventing the next pandemic – Zoonotic diseases and how to break the chain of transmission |url=https://www.unenvironment.org/resources/report/preventing-future-zoonotic-disease-outbreaks-protecting-environment-animals-and |website=United Nations Environmental Programme |date=15 May 2020 |publisher=United Nations |access-date=7 July 2020 |archive-date=6 July 2020 |archive-url=https://web.archive.org/web/20200706201638/https://www.unenvironment.org/resources/report/preventing-future-zoonotic-disease-outbreaks-protecting-environment-animals-and |url-status=live }}</ref>

===Contamination of food or water supply===
Foodborne zoonotic diseases are caused by a variety of pathogens that can affect both humans and animals. The most significant zoonotic pathogens causing foodborne diseases are:

==== Bacterial pathogens ====
[[Escherichia coli O157:H7|''Escherichia coli'' O157:H7]], ''[[Campylobacter]]'', ''[[Caliciviridae]]'', and ''[[Salmonella]]''.<ref name="czpf">{{cite journal | vauthors = Humphrey T, O'Brien S, Madsen M | title = Campylobacters as zoonotic pathogens: a food production perspective | journal = International Journal of Food Microbiology | volume = 117 | issue = 3 | pages = 237–257 | date = July 2007 | pmid = 17368847 | doi = 10.1016/j.ijfoodmicro.2007.01.006 }}</ref><ref name="iear">{{cite journal | vauthors = Cloeckaert A | title = Introduction: emerging antimicrobial resistance mechanisms in the zoonotic foodborne pathogens Salmonella and Campylobacter | journal = Microbes and Infection | volume = 8 | issue = 7 | pages = 1889–1890 | date = June 2006 | pmid = 16714136 | doi = 10.1016/j.micinf.2005.12.024 | doi-access = free }}</ref><ref name="tpge">{{cite journal | vauthors = Murphy FA | title = The threat posed by the global emergence of livestock, food-borne, and zoonotic pathogens | journal = Annals of the New York Academy of Sciences | volume = 894 | issue = 1 | pages = 20–27 | year = 1999 | pmid = 10681965 | doi = 10.1111/j.1749-6632.1999.tb08039.x | s2cid = 13384121 | bibcode = 1999NYASA.894...20M }}</ref>

====Viral pathogens====

* Hepatitis E: Hepatitis E virus (HEV) is primarily transmitted through pork products, especially in developing countries with limited sanitation. The infection can lead to acute liver disease and is particularly dangerous for pregnant women.<ref name=":2" />
* Norovirus: Often found in contaminated shellfish and fresh produce, norovirus is a leading cause of foodborne illness globally. It spreads easily and causes symptoms like vomiting, diarrhea, and stomach pain.<ref>{{Cite journal |last1=Ushijima |first1=Hiroshi |last2=Fujimoto |first2=Tsuguto |last3=Müller |first3=Werner EG |last4=Hayakawa |first4=Satoshi |date=2014 |title=Norovirus and Foodborne Disease: A Review |url=https://www.jstage.jst.go.jp/article/foodsafetyfscj/2/3/2_2014027/_article |journal=Food Safety |volume=2 |issue=3 |pages=37–54 |doi=10.14252/foodsafetyfscj.2014027}}</ref>

====Parasitic pathogens====

* ''Toxoplasma gondii'': This parasite is commonly found in undercooked meat, especially pork and lamb, and can cause toxoplasmosis. While typically mild, toxoplasmosis can be severe in immunocompromised individuals and pregnant women, potentially leading to complications.<ref>{{Cite journal |last1=Marín-García |first1=Pablo-Jesús |last2=Planas |first2=Nuria |last3=Llobat |first3=Lola |date=January 2022 |title=Toxoplasma gondii in Foods: Prevalence, Control, and Safety |journal=Foods |language=en |volume=11 |issue=16 |page=2542 |doi=10.3390/foods11162542 |doi-access=free |pmid=36010541 |pmc=9407268 |issn=2304-8158}}</ref>
*''Trichinella'' spp. is transmitted through undercooked pork and wild game, causing trichinellosis. Symptoms range from mild gastrointestinal distress to severe muscle pain and, in rare cases, can be fatal.<ref>{{Cite journal |last1=Noeckler |first1=Karsten |last2=Pozio |first2=Edoardo |last3=van der Giessen |first3=Joke |last4=Hill |first4=Dolores E. |last5=Gamble |first5=H. Ray |date=2019-03-01 |title=International Commission on Trichinellosis: Recommendations on post-harvest control of Trichinella in food animals |journal=Food and Waterborne Parasitology |volume=14 |article-number=e00041 |doi=10.1016/j.fawpar.2019.e00041 |pmid=32095607 |pmc=7033995 |issn=2405-6766}}</ref>

=== Farming, ranching and animal husbandry ===
{{see also|Intensive animal farming#Human health impact}}
Contact with farm animals can lead to disease in farmers or others that come into contact with infected farm animals. [[Glanders]] primarily affects those who work closely with horses and donkeys. Close contact with cattle can lead to [[Anthrax#Cause|cutaneous anthrax]] infection, whereas [[Anthrax#Cause|inhalation anthrax]] infection is more common for workers in [[slaughterhouse]]s, [[tannery|tanneries]], and [[wool mill]]s.<ref>{{cite web|url=https://www.cdc.gov/anthrax/basics/types/inhalation.html|title=Inhalation Anthrax|website=[[cdc.gov]]|archive-url=https://web.archive.org/web/20170326230905/https://www.cdc.gov/anthrax/basics/types/inhalation.html|archive-date=26 March 2017|access-date=26 March 2017|url-status=live}}</ref> Close contact with sheep who have recently given birth can lead to infection with the bacterium ''[[Chlamydia psittaci]],'' causing chlamydiosis (and [[enzootic abortion]] in pregnant women), as well as increase the risk of [[Q fever]], [[toxoplasmosis]], and [[listeriosis]], in the pregnant or otherwise [[immunocompromised]]. [[Echinococcosis]] is caused by a tapeworm, which can spread from infected sheep by food or water contaminated by feces or wool. [[Avian influenza]] is common in chickens, and, while it is rare in humans, the main public health worry is that a strain of avian influenza will recombine with a human influenza virus and cause a pandemic like the [[1918 flu pandemic|1918 Spanish flu]].<ref>{{Cite journal |last1=Peiris |first1=J. S. Malik |last2=de Jong |first2=Menno D. |last3=Guan |first3=Yi |date=April 2007 |title=Avian Influenza Virus (H5N1): a Threat to Human Health |journal=Clinical Microbiology Reviews |volume=20 |issue=2 |pages=243–267 |doi=10.1128/cmr.00037-06 |pmid=17428885 |pmc=1865597 |issn=0893-8512}}</ref> In 2017, [[Free range|free-range]] chickens in the UK were temporarily ordered to remain inside due to the threat of avian influenza.<ref>{{cite news|url=https://www.bbc.co.uk/bnews/uk-wales-politics-39103191|title=Avian flu: Poultry to be allowed outside under new rules|date=28 February 2017|work=BBC News|access-date=26 March 2017|archive-url=https://web.archive.org/web/20170307040605/http://www.bbc.co.uk/news/uk-wales-politics-39103191|archive-date=7 March 2017}}</ref> Cattle are an important reservoir of [[cryptosporidiosis]],<ref>{{cite journal | vauthors = Lassen B, Ståhl M, Enemark HL | title = Cryptosporidiosis - an occupational risk and a disregarded disease in Estonia | journal = Acta Veterinaria Scandinavica | volume = 56 | issue = 1 | page = 36 | date = June 2014 | pmid = 24902957 | pmc = 4089559 | doi = 10.1186/1751-0147-56-36 | doi-access = free }}</ref> which mainly affects the immunocompromised. Reports have shown [[mink]] can also become infected.<ref>{{cite news|url=https://news.yahoo.com/mink-found-coronavirus-two-dutch-114943885.html|title=Mink found to have coronavirus on two Dutch farms – ministry|date=26 April 2020|agency=Reuters|access-date=27 April 2020|archive-url=https://web.archive.org/web/20200427142458/https://news.yahoo.com/mink-found-coronavirus-two-dutch-114943885.html|archive-date=27 April 2020|url-status=live}}</ref> In Western countries, [[hepatitis E]] burden is largely dependent on exposure to animal products, and pork is a significant source of infection, in this respect.<ref name=":2">{{cite journal | vauthors = Li TC, Chijiwa K, Sera N, Ishibashi T, Etoh Y, Shinohara Y, Kurata Y, Ishida M, Sakamoto S, Takeda N, Miyamura T | display-authors = 6 | title = Hepatitis E virus transmission from wild boar meat | journal = Emerging Infectious Diseases | volume = 11 | issue = 12 | pages = 1958–1960 | date = December 2005 | pmid = 16485490 | pmc = 8606544 | doi = 10.1016/j.onehlt.2021.100350 | doi-access = free }}</ref> Similarly, the [[human coronavirus OC43]], the main cause of the common cold, can use the pig as a zoonotic reservoir,<ref>{{cite journal | vauthors = Xu G, Qiao Z, Schraauwen R, Avan A, Peppelenbosch MP, Bijvelds MJ, Jiang S,,Li P | title = Evidence for cross-species transmission of human coronavirus OC43 through bioinformatics and modeling infections in porcine intestinal organoids. | journal = Veterinary Microbiology | volume = 293 | article-number = 110101 | date = April 2024 | pmid = 38718529 | doi = 10.1016/j.vetmic.2024.110101| doi-access = free }}</ref> constantly reinfecting the human population.

[[Veterinary physician|Veterinarians]] are exposed to unique [[occupational hazard]]s when it comes to zoonotic disease. In the US, studies have highlighted an increased risk of injuries and lack of veterinary awareness of these hazards. Research has proved the importance for continued clinical veterinarian education on occupational risks associated with [[musculoskeletal]] injuries, animal bites, needle-sticks, and cuts.<ref>{{cite journal | vauthors = Rood KA, Pate ML | title = Assessment of Musculoskeletal Injuries Associated with Palpation, Infection Control Practices, and Zoonotic Disease Risks among Utah Clinical Veterinarians | journal = Journal of Agromedicine | volume = 24 | issue = 1 | pages = 35–45 | date = January 2019 | pmid = 30362924 | doi = 10.1080/1059924X.2018.1536574 | s2cid = 53092026 }}</ref>

A July 2020 report by the [[United Nations Environment Programme]] stated that the increase in zoonotic pandemics is directly attributable to [[Human impact on the environment#Ecosystem impacts|anthropogenic destruction of nature]] and the increased global demand for meat and that the [[Industrial meat production|industrial farming]] of pigs and chickens in particular will be a primary risk factor for the spillover of zoonotic diseases in the future.<ref>{{cite news | vauthors = Carrington D |date=6 July 2020 |title=Coronavirus: world treating symptoms, not cause of pandemics, says UN |url=https://www.theguardian.com/world/2020/jul/06/coronavirus-world-treating-symptoms-not-cause-pandemics-un-report |work=The Guardian |access-date=7 July 2020 |archive-date=7 July 2020 |archive-url=https://web.archive.org/web/20200707004708/https://www.theguardian.com/world/2020/jul/06/coronavirus-world-treating-symptoms-not-cause-pandemics-un-report |url-status=live }}</ref> Habitat loss of viral reservoir species has been identified as a significant source in at least one [[Spillover infection|spillover event]].<ref>{{citation |last=von Csefalvay |first=Chris |title=Host-vector and multihost systems |date=2023 |url=https://linkinghub.elsevier.com/retrieve/pii/B978032395389400013X |work=Computational Modeling of Infectious Disease |pages=121–149 |access-date=6 March 2023 |publisher=Elsevier |doi=10.1016/b978-0-32-395389-4.00013-x |isbn=978-0-323-95389-4|url-access=subscription }}</ref>

=== Wildlife trade or animal attacks ===
The wildlife trade may increase spillover risk because it directly increases the number of interactions across animal species, sometimes in small spaces.<ref>{{cite journal | vauthors = Glidden CK, Nova N, Kain MP, Lagerstrom KM, Skinner EB, Mandle L, Sokolow SH, Plowright RK, Dirzo R, De Leo GA, Mordecai EA | display-authors = 6 | title = Human-mediated impacts on biodiversity and the consequences for zoonotic disease spillover | journal = Current Biology | volume = 31 | issue = 19 | pages = R1342–R1361 | date = October 2021 | pmid = 34637744 | doi = 10.1016/j.cub.2021.08.070 | s2cid = 238588772 | pmc = 9255562 | bibcode = 2021CBio...31R1342G }}</ref> The origin of the [[COVID-19 pandemic]]<ref name="BJC_Beirne2021">{{cite journal | vauthors = You M | title = Changes of China's regulatory regime on commercial artificial breeding of terrestrial wildlife in time of COVID-19 outbreak and impacts on the future | journal = Biological Conservation | volume = 250 | issue = 3 | page = 108756 | date = October 2020 | pmc = 7953978 | doi = 10.1093/bjc/azaa084 | publisher = Oxford University Press | jfm =  | zbl =  | jstor =  | pmid = 32863392 | mr =  }}</ref><ref name="CovidAndCapital">{{cite journal | vauthors = Blattner C, Coulter K, Wadiwel D, Kasprzycka E | title = Covid-19 and Capital: Labour Studies and Nonhuman Animals – A Roundtable Dialogue | journal = Animal Studies Journal | volume = 10 | issue = 1 | pages = 240–272 | publisher = University of Wollongong | date = 2021 | url = https://ro.uow.edu.au/asj/vol10/iss1/11/ | jstor = | issn = 2201-3008 | doi = 10.14453/asj.v10i1.10 | id = | mr = | zbl = | jfm = | access-date = 19 September 2021| doi-access = free }}</ref> is traced to the [[wet markets in China]].<ref name="SunEtAl_2020">{{cite journal | vauthors = Sun J, He WT, Wang L, Lai A, Ji X, Zhai X, Li G, Suchard MA, Tian J, Zhou J, Veit M, Su S | display-authors = 6 | title = COVID-19: Epidemiology, Evolution, and Cross-Disciplinary Perspectives | journal = Trends in Molecular Medicine | volume = 26 | issue = 5 | pages = 483–495 | date = May 2020 | pmid = 32359479 | pmc = 7118693 | doi = 10.1016/j.molmed.2020.02.008 | name-list-style = vanc }}</ref><ref name="WHOPoints_2021">{{cite news |title=WHO Points To Wildlife Farms In Southern China As Likely Source Of Pandemic |url=https://www.npr.org/sections/goatsandsoda/2021/03/15/977527808/who-points-to-wildlife-farms-in-southwest-china-as-likely-source-of-pandemic?t=1616302540855 |publisher=[[NPR]] |date=15 March 2021}}</ref><ref name="Maxmen_2021">{{cite journal | vauthors = Maxmen A | title = WHO report into COVID pandemic origins zeroes in on animal markets, not labs | journal = Nature | volume = 592 | issue = 7853 | pages = 173–174 | date = April 2021 | pmid = 33785930 | doi = 10.1038/d41586-021-00865-8 | s2cid = 232429241 | bibcode = 2021Natur.592..173M }}</ref><ref>{{Cite journal |last1=Huang |first1=Chaolin |last2=Wang |first2=Yeming |last3=Li |first3=Xingwang |last4=Ren |first4=Lili |last5=Zhao |first5=Jianping |last6=Hu |first6=Yi |last7=Zhang |first7=Li |last8=Fan |first8=Guohui |last9=Xu |first9=Jiuyang |last10=Gu |first10=Xiaoying |last11=Cheng |first11=Zhenshun |last12=Yu |first12=Ting |last13=Xia |first13=Jiaan |last14=Wei |first14=Yuan |last15=Wu |first15=Wenjuan |date=2020-02-15 |title=Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China |journal=Lancet |volume=395 |issue=10223 |pages=497–506 |doi=10.1016/S0140-6736(20)30183-5 |issn=1474-547X |pmc=7159299 |pmid=31986264}}</ref>

Zoonotic disease emergence is demonstrably linked to the consumption of wildlife meat, exacerbated by human encroachment into natural habitats and amplified by the unsanitary conditions of wildlife markets.<ref>{{Cite journal |last1=Karesh |first1=William B. |last2=Cook |first2=Robert A. |last3=Bennett |first3=Elizabeth L. |last4=Newcomb |first4=James |date=July 2005 |title=Wildlife trade and global disease emergence |journal=Emerging Infectious Diseases |volume=11 |issue=7 |pages=1000–1002 |doi=10.3201/eid1107.050194 |issn=1080-6040 |pmc=3371803 |pmid=16022772}}</ref><ref>{{Cite web |title=Zoonotic Pathogens in Wildlife Traded in Markets for Human Consumption, Laos |url=https://wwwnc.cdc.gov/eid/404.html?aspxerrorpath=/eid/article/28/4/21-0249_article |access-date=2025-05-15 |website=cdc.gov}}</ref> These markets, where diverse species converge, facilitate the mixing and transmission of pathogens, including those responsible for outbreaks of [[HIV-1 protease|HIV-1]],<ref>{{Cite journal |last1=Hahn |first1=B. H. |last2=Shaw |first2=G. M. |last3=De Cock |first3=K. M. |last4=Sharp |first4=P. M. |date=2000-01-28 |title=AIDS as a zoonosis: scientific and public health implications |journal=Science |volume=287 |issue=5453 |pages=607–614 |doi=10.1126/science.287.5453.607 |issn=0036-8075 |pmid=10649986|bibcode=2000Sci...287..607H }}</ref> [[Ebola]],<ref>{{Cite journal |last1=Leroy |first1=Eric M. |last2=Rouquet |first2=Pierre |last3=Formenty |first3=Pierre |last4=Souquière |first4=Sandrine |last5=Kilbourne |first5=Annelisa |last6=Froment |first6=Jean-Marc |last7=Bermejo |first7=Magdalena |last8=Smit |first8=Sheilag |last9=Karesh |first9=William |last10=Swanepoel |first10=Robert |last11=Zaki |first11=Sherif R. |last12=Rollin |first12=Pierre E. |date=2004-01-16 |title=Multiple Ebola virus transmission events and rapid decline of central African wildlife |journal=Science |volume=303 |issue=5656 |pages=387–390 |doi=10.1126/science.1092528 |issn=1095-9203 |pmid=14726594|bibcode=2004Sci...303..387L |s2cid=43305484 }}</ref> and [[mpox]],<ref>{{Cite journal |last1=Reed |first1=Kurt D. |last2=Melski |first2=John W. |last3=Graham |first3=Mary Beth |last4=Regnery |first4=Russell L. |last5=Sotir |first5=Mark J. |last6=Wegner |first6=Mark V. |last7=Kazmierczak |first7=James J. |last8=Stratman |first8=Erik J. |last9=Li |first9=Yu |last10=Fairley |first10=Janet A. |last11=Swain |first11=Geoffrey R. |last12=Olson |first12=Victoria A. |last13=Sargent |first13=Elizabeth K. |last14=Kehl |first14=Sue C. |last15=Frace |first15=Michael A. |date=2004-01-22 |title=The detection of monkeypox in humans in the Western Hemisphere |journal=The New England Journal of Medicine |volume=350 |issue=4 |pages=342–350 |doi=10.1056/NEJMoa032299 |issn=1533-4406 |pmid=14736926}}</ref> and potentially even the [[COVID-19 pandemic]].<ref>{{Cite journal |last1=Li |first1=Xiaojun |last2=Giorgi |first2=Elena E. |last3=Marichannegowda |first3=Manukumar Honnayakanahalli |last4=Foley |first4=Brian |last5=Xiao |first5=Chuan |last6=Kong |first6=Xiang-Peng |last7=Chen |first7=Yue |last8=Gnanakaran |first8=S. |last9=Korber |first9=Bette |last10=Gao |first10=Feng |date=July 2020 |title=Emergence of SARS-CoV-2 through recombination and strong purifying selection |journal=Science Advances |volume=6 |issue=27 |article-number=eabb9153 |doi=10.1126/sciadv.abb9153 |issn=2375-2548 |pmc=7458444 |pmid=32937441|bibcode=2020SciA....6.9153L }}</ref> Notably, small mammals often harbor a vast array of zoonotic bacteria and viruses,<ref>{{Cite journal |last1=Mills |first1=J. N. |last2=Childs |first2=J. E. |date=1998 |title=Ecologic studies of rodent reservoirs: their relevance for human health |journal=Emerging Infectious Diseases |volume=4 |issue=4 |pages=529–537 |doi=10.3201/eid0404.980403 |issn=1080-6040 |pmc=2640244 |pmid=9866729}}</ref> yet endemic bacterial transmission among wildlife remains largely unexplored. Therefore, accurately determining the pathogenic landscape of traded wildlife is crucial for guiding effective measures to combat zoonotic diseases and documenting the societal and environmental costs associated with this practice.

=== Insect vectors ===
* [[African sleeping sickness]]
* [[Dirofilariasis]]
* [[Eastern equine encephalitis]]
* [[Japanese encephalitis]]
* [[Saint Louis encephalitis]]
* [[Scrub typhus]]
* [[Tularemia]]
* [[Venezuelan equine encephalitis]]
* [[West Nile fever]]
* [[Western equine encephalitis]]
* [[Zika fever]]

=== Pets ===
{{Further|Feline zoonosis}}
Pets can transmit a number of diseases. Dogs and cats are routinely vaccinated against [[rabies]]. Pets can also transmit [[ringworm]] and ''[[Giardia]]'', which are endemic in both animal and human populations. [[Toxoplasmosis]] is a common infection of cats; in humans it is a mild disease although it can be dangerous to pregnant women.<ref>{{cite web|url=https://www.cdc.gov/parasites/toxoplasmosis/gen_info/pregnant.html|title=Toxoplasmosis – General Information – Pregnant Women|last=Prevention|first=CDC – Centers for Disease Control and|website=cdc.gov|archive-url=https://web.archive.org/web/20151118053645/http://www.cdc.gov/parasites/toxoplasmosis/gen_info/pregnant.html|archive-date=18 November 2015|access-date=1 April 2017|url-status=live}}</ref> [[Dirofilariasis]] is caused by ''[[Dirofilaria immitis]]'' through mosquitoes infected by mammals like dogs and cats. [[Cat-scratch disease]] is caused by ''[[Bartonella henselae]]'' and ''[[Bartonella quintana]]'', which are transmitted by fleas that are endemic to cats. [[Toxocariasis]] is the infection of humans by any of species of [[roundworm]], including species specific to dogs (''[[Toxocara canis]])'' or cats (''[[Toxocara cati]]''). [[Cryptosporidiosis]] can be spread to humans from pet lizards, such as the [[leopard gecko]]. ''[[Encephalitozoon cuniculi]]'' is a [[microsporidia]]l parasite carried by many mammals, including rabbits, and is an important [[opportunistic infection|opportunistic pathogen]] in people [[immunodeficiency|immunocompromised]] by [[HIV/AIDS]], [[organ transplantation]], or [[CD4+ T cells and antitumor immunity|CD4+ T-lymphocyte]] deficiency.<ref name=Weese2011>{{cite book | vauthors = Weese JS |title=Companion animal zoonoses |date=2011 |publisher=Wiley-Blackwell |isbn=978-0-8138-1964-8 |pages=282–84}}</ref>

Pets may also serve as a reservoir of viral disease and contribute to the chronic presence of certain viral diseases in the human population. For instance, approximately 20% of domestic dogs, cats, and horses carry anti-hepatitis E virus [[antibodies]] and thus these animals probably contribute to human hepatitis E burden as well.<ref>{{cite journal | vauthors = Li Y, Qu C, Spee B, Zhang R, Penning LC, de Man RA, Peppelenbosch MP, Fieten H, Pan Q | display-authors = 6 | title = Hepatitis E virus seroprevalence in pets in the Netherlands and the permissiveness of canine liver cells to the infection | journal = Irish Veterinary Journal | volume = 73 | article-number = 6 | year = 2020 | pmid = 32266057 | pmc = 7119158 | doi = 10.1186/s13620-020-00158-y | doi-access = free }}</ref> For non-vulnerable populations (e.g., people who are not immunocompromised) the associated disease burden is, however, small.<ref>{{Cite web |title=Hepatitis E |url=https://www.who.int/news-room/fact-sheets/detail/hepatitis-e |access-date=2023-10-26 |website=www.who.int |language=en}}</ref><ref>{{Cite journal |last1=Zahmanova |first1=Gergana |last2=Takova |first2=Katerina |last3=Tonova |first3=Valeria |last4=Koynarski |first4=Tsvetoslav |last5=Lukov |first5=Laura L. |last6=Minkov |first6=Ivan |last7=Pishmisheva |first7=Maria |last8=Kotsev |first8=Stanislav |last9=Tsachev |first9=Ilia |last10=Baymakova |first10=Magdalena |last11=Andonov |first11=Anton P. |date=2023-07-16 |title=The Re-Emergence of Hepatitis E Virus in Europe and Vaccine Development |journal=Viruses |volume=15 |issue=7 |page=1558 |doi=10.3390/v15071558 |doi-access=free |pmid=37515244 |issn=1999-4915|pmc=10383931 }}</ref> Furthermore, the trade of non-domestic animals such as wild animals as pets can also increase the risk of zoonosis spread.<ref>{{Cite journal |last1=D'Cruze |first1=Neil |last2=Green |first2=Jennah |last3=Elwin |first3=Angie |last4=Schmidt-Burbach |first4=Jan |date=December 2020 |title=Trading Tactics: Time to Rethink the Global Trade in Wildlife |journal=Animals |language=en |volume=10 |issue=12 |page=2456 |doi=10.3390/ani10122456 |doi-access=free |pmid=33371486 |pmc=7767496 |issn=2076-2615}}</ref><ref>{{Cite journal |last1=Aguirre |first1=A. Alonso |last2=Catherina |first2=Richard |last3=Frye |first3=Hailey |last4=Shelley |first4=Louise |date=September 2020 |title=Illicit Wildlife Trade, Wet Markets, and COVID-19: Preventing Future Pandemics |journal=World Medical & Health Policy |language=en |volume=12 |issue=3 |pages=256–265 |doi=10.1002/wmh3.348 |issn=1948-4682 |pmc=7362142 |pmid=32837772}}</ref>

Bats are frequently unjustly portrayed as the primary instigators of the ongoing COVID-19 epidemic; nevertheless, the true origins of this and other zoonotic spillover occurrences should be attributed to human environmental impacts, especially the proliferation of pets.<ref name=":3" /> For example, bat predation by cats poses a significant danger to biodiversity conservation and carries zoonotic consequences that must be acknowledged.<ref name=":3" />

=== Exhibition ===
[[Outbreak]]s of zoonoses have been traced to human interaction with, and exposure to, other animals at [[fair]]s, [[wet market|live animal markets]],<ref>{{cite journal | vauthors = Chomel BB, Belotto A, Meslin FX | title = Wildlife, exotic pets, and emerging zoonoses | journal = Emerging Infectious Diseases | volume = 13 | issue = 1 | pages = 6–11 | date = January 2007 | pmid = 17370509 | pmc = 2725831 | doi = 10.3201/eid1301.060480 }}</ref> [[petting zoo]]s, and other settings. In 2005, the [[Centers for Disease Control and Prevention]] (CDC) issued an updated list of recommendations for preventing zoonosis transmission in public settings.<ref>{{cite journal |author=Centers for Disease Control and Prevention |title=Compendium of Measures To Prevent Disease Associated with Animals in Public Settings, 2005: National Association of State Public Health Veterinarians, Inc. (NASPHV) |journal=MMWR |volume=54 |issue=RR–4 |pages=inclusive page numbers |year=2005 |url=https://www.cdc.gov/mmwr/PDF/rr/rr5404.pdf |access-date=28 December 2008 |archive-url=https://web.archive.org/web/20081217113423/http://www.cdc.gov/mmwr/PDF/rr/rr5404.pdf |archive-date=17 December 2008 |url-status=live }}</ref> The recommendations, developed in conjunction with the [[National Association of State Public Health Veterinarians]],<ref>{{cite web|url=http://www.nasphv.org/|title=NASPHV – National Association of Public Health Veterinarians|website=www.nasphv.org|access-date=29 May 2007|archive-date=23 July 2010|archive-url=https://web.archive.org/web/20100723000130/http://www.nasphv.org/|url-status=live}}</ref> include educational responsibilities of venue operators, limiting public animal contact, and animal care and management.

=== Hunting and bushmeat ===
{{Main|Hunting|Bushmeat}}
[[Hunting]] involves humans tracking, chasing, and capturing wild animals, primarily for food or materials like fur. However, other reasons like pest control or managing wildlife populations can also exist. Transmission of zoonotic diseases, those leaping from animals to humans, can occur through various routes: direct physical contact, airborne droplets or particles, bites or vector transport by insects, oral ingestion, or even contact with contaminated environments.<ref>{{Citation |last1=Murray |first1=Kris A. |title=Emerging Viral Zoonoses from Wildlife Associated with Animal-Based Food Systems: Risks and Opportunities |date=2016 |work=Food Safety Risks from Wildlife: Challenges in Agriculture, Conservation, and Public Health |pages=31–57 |editor-last=Jay-Russell |editor-first=Michele |series=Food Microbiology and Food Safety |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-24442-6_2 |isbn=978-3-319-24442-6 |last2=Allen |first2=Toph |last3=Loh |first3=Elizabeth |last4=Machalaba |first4=Catherine |last5=Daszak |first5=Peter |editor2-last=Doyle |editor2-first=Michael P.|doi-access=free }}</ref> Wildlife activities like hunting and trade bring humans closer to dangerous zoonotic pathogens, threatening global health.<ref name="Problematic Wildlife">{{Cite book |last1=Kurpiers |first1=Laura A. |last2=Schulte-Herbrüggen |first2=Björn |last3=Ejotre |first3=Imran |last4=Reeder |first4=DeeAnn M. |chapter=Bushmeat and Emerging Infectious Diseases: Lessons from Africa |date=2015-09-21 |title=Problematic Wildlife |pages=507–551 |doi=10.1007/978-3-319-22246-2_24 |pmc=7123567|isbn=978-3-319-22245-5 }}</ref>

According to the Center for Diseases Control and Prevention (CDC) hunting and consuming wild animal meat ("bushmeat") in regions like Africa can expose people to infectious diseases due to the types of animals involved, like bats and primates. Unfortunately, common preservation methods like smoking or drying aren't enough to eliminate these risks.<ref>{{Cite web |date=2022-11-21 |title=Bushmeat Importation Policies {{!}} CDC |url=https://www.cdc.gov/importation/bushmeat.html |access-date=2024-01-12 |website=www.cdc.gov |language=en-us}}</ref> Although bushmeat provides protein and income for many, the practice is intricately linked to numerous emerging infectious diseases like Ebola, HIV, and [[SARS]], raising critical public health concerns.<ref name="Problematic Wildlife"/>

A review published in 2022 found evidence that zoonotic spillover linked to wildmeat consumption has been reported across all continents.<ref>{{Cite journal |last1=Milbank |first1=Charlotte |last2=Vira |first2=Bhaskar |date=May 2022 |title=Wildmeat consumption and zoonotic spillover: contextualising disease emergence and policy responses |journal=The Lancet. Planetary Health |volume=6 |issue=5 |pages=e439–e448 |doi=10.1016/S2542-5196(22)00064-X |issn=2542-5196 |pmc=9084621 |pmid=35550083}}</ref>

===Deforestation, biodiversity loss and environmental degradation===
{{Main|Deforestation| Biodiversity loss|Environmental degradation}}
[[Kate Jones (scientist)|Kate Jones]], Chair of Ecology and Biodiversity at [[University College London]], says zoonotic diseases are increasingly linked to environmental change and human behavior. The disruption of pristine forests driven by logging, mining, road building through remote places, rapid urbanization, and population growth is bringing people into closer contact with animal species they may never have been near before. The resulting transmission of disease from wildlife to humans, she says, is now "a hidden cost of human economic development".<ref>{{cite news| vauthors = Vidal J |url=https://www.theguardian.com/environment/2020/mar/18/tip-of-the-iceberg-is-our-destruction-of-nature-responsible-for-covid-19-aoe|title='Tip of the iceberg': is our destruction of nature responsible for Covid-19?|date=18 March 2020|work=The Guardian|access-date=18 March 2020|issn=0261-3077|archive-date=20 March 2020|archive-url=https://web.archive.org/web/20200320095435/https://www.theguardian.com/environment/2020/mar/18/tip-of-the-iceberg-is-our-destruction-of-nature-responsible-for-covid-19-aoe|url-status=live}}</ref> In a guest article, published by [[IPBES]], President of the [[EcoHealth Alliance]] and zoologist [[Peter Daszak]], along with three co-chairs of the 2019 ''[[Global Assessment Report on Biodiversity and Ecosystem Services]]'', Josef Settele, [[Sandra Díaz (ecologist)|Sandra Díaz]], and Eduardo Brondizio, wrote that "rampant deforestation, uncontrolled expansion of agriculture, [[intensive farming]], mining and infrastructure development, as well as the exploitation of wild species have created a 'perfect storm' for the spillover of diseases from wildlife to people."<ref>{{cite news | vauthors = Carrington D |date=27 April 2020 |title=Halt destruction of nature or suffer even worse pandemics, say world's top scientists |url=https://www.theguardian.com/world/2020/apr/27/halt-destruction-nature-worse-pandemics-top-scientists |work=The Guardian |access-date=27 April 2020 |archive-date=15 May 2020 |archive-url=https://web.archive.org/web/20200515015940/https://www.theguardian.com/world/2020/apr/27/halt-destruction-nature-worse-pandemics-top-scientists |url-status=live }}</ref>

Joshua Moon, Clare Wenham, and Sophie Harman said that there is evidence that decreased biodiversity has an effect on the diversity of hosts and frequency of human-animal interactions with potential for pathogenic spillover.<ref>{{cite journal | vauthors = Moon J, Wenham C, Harman S | title = SAGO has a politics problem, and WHO is ignoring it | journal = BMJ | volume = 375 | article-number = n2786 | date = November 2021 | pmid = 34772656 | doi = 10.1136/bmj.n2786 | s2cid = 244041854 | doi-access = free }}</ref>

An April 2020 study, published in the ''[[Proceedings of the Royal Society]]''{{'s}} [[Proceedings of the Royal Society#Proceedings of the Royal Society B: Biological Sciences|Part B]] journal, found that increased virus spillover events from animals to humans can be linked to [[biodiversity loss]] and [[environmental degradation]], as humans further encroach on wildlands to engage in agriculture, hunting, and resource extraction they become exposed to pathogens which normally would remain in these areas. Such spillover events have been tripling every decade since 1980.<ref>{{cite news | vauthors = Shield C |title=Coronavirus Pandemic Linked to Destruction of Wildlife and World's Ecosystems |url=https://www.dw.com/en/coronavirus-pandemic-linked-to-destruction-of-wildlife-and-worlds-ecosystems/a-53078480 |access-date=16 April 2020 |agency=[[Deutsche Welle]] |date=16 April 2020 |archive-date=16 April 2020 |archive-url=https://web.archive.org/web/20200416034115/https://www.dw.com/en/coronavirus-pandemic-linked-to-destruction-of-wildlife-and-worlds-ecosystems/a-53078480 |url-status=live }}</ref> An August 2020 study, published in ''[[Nature (journal)|Nature]]'', concludes that the [[Anthropogenic effect|anthropogenic]] destruction of ecosystems for the purpose of expanding agriculture and human settlements reduces biodiversity and allows for smaller animals such as bats and rats, which are more adaptable to human pressures and also carry the most zoonotic diseases, to proliferate. This in turn can result in more pandemics.<ref>{{cite news | vauthors = Carrington D |date=5 August 2020 |title=Deadly diseases from wildlife thrive when nature is destroyed, study finds |url=https://www.theguardian.com/environment/2020/aug/05/deadly-diseases-from-wildlife-thrive-when-nature-is-destroyed-study-finds |work=The Guardian |access-date=7 August 2020 |archive-date=6 August 2020 |archive-url=https://web.archive.org/web/20200806223417/https://www.theguardian.com/environment/2020/aug/05/deadly-diseases-from-wildlife-thrive-when-nature-is-destroyed-study-finds |url-status=live }}</ref>

In October 2020, the [[Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services]] published its report on the 'era of pandemics' by 22 experts in a variety of fields and concluded that anthropogenic destruction of [[biodiversity]] is paving the way to the pandemic era and could result in as many as 850,000 viruses being transmitted from animals – in particular birds and mammals – to humans. The increased pressure on ecosystems is being driven by the "exponential rise" in consumption and trade of commodities such as meat, [[palm oil]], and metals, largely facilitated by developed nations, and by a [[Population growth|growing human population]]. According to Peter Daszak, the chair of the group who produced the report, "there is no great mystery about the cause of the Covid-19 pandemic, or of any modern pandemic. The same human activities that drive [[climate change and biodiversity loss]] also drive pandemic risk through their impacts on our environment."<ref>{{cite news | vauthors = Woolaston K, Fisher JL |date=29 October 2020 |title=UN report says up to 850,000 animal viruses could be caught by humans, unless we protect nature |url=https://theconversation.com/un-report-says-up-to-850-000-animal-viruses-could-be-caught-by-humans-unless-we-protect-nature-148911 |work=[[The Conversation (website)|The Conversation]] |access-date=29 October 2020 |archive-date=1 November 2020 |archive-url=https://web.archive.org/web/20201101051450/https://theconversation.com/un-report-says-up-to-850-000-animal-viruses-could-be-caught-by-humans-unless-we-protect-nature-148911 |url-status=live }}</ref><ref>{{cite news | vauthors = Carrington D |date=29 October 2020 |title=Protecting nature is vital to escape 'era of pandemics' – report |url=https://www.theguardian.com/environment/2020/oct/29/protecting-nature-vital-pandemics-report-outbreaks-wild |work=The Guardian |access-date=29 October 2020 |archive-date=29 October 2020 |archive-url=https://web.archive.org/web/20201029144031/https://www.theguardian.com/environment/2020/oct/29/protecting-nature-vital-pandemics-report-outbreaks-wild |url-status=live }}</ref><ref>{{cite news |author=<!--Staff writer(s); no by-line.--> |date=29 October 2020 |title=Escaping the 'Era of Pandemics': experts warn worse crises to come; offer options to reduce risk |url=https://www.eurekalert.org/pub_releases/2020-10/tca-et102820.php |work=EurekAlert! |access-date=29 October 2020 |archive-date=17 November 2020 |archive-url=https://web.archive.org/web/20201117010851/https://www.eurekalert.org/pub_releases/2020-10/tca-et102820.php |url-status=live }}</ref>

=== Climate change ===
{{Further|Climate change and infectious diseases}}
According to a report from the [[United Nations Environment Programme]] and [[International Livestock Research Institute]], entitled "Preventing the next pandemic – Zoonotic diseases and how to break the chain of transmission", climate change is one of the 7 human-related causes of the increase in the number of zoonotic diseases.<ref name="bbc.com" /><ref name="United Nations" /> The University of Sydney issued a study, in March 2021, that examines factors increasing the likelihood of [[epidemic]]s and pandemics like the COVID-19 pandemic. The researchers found that "pressure on ecosystems, climate change and economic development are key factors" in doing so. More zoonotic diseases were found in [[High-income country|high-income countries]].<ref>{{cite web |title=Factors that may predict next pandemic |url=https://www.sciencedaily.com/releases/2021/03/210330092524.htm |website=ScienceDaily |publisher=University of Sydney |access-date=19 May 2021 |archive-date=19 May 2021 |archive-url=https://web.archive.org/web/20210519091224/https://www.sciencedaily.com/releases/2021/03/210330092524.htm |url-status=live }}</ref>

A 2022 study dedicated to the link between climate change and zoonosis found a strong link between climate change and the epidemic emergence in the last 15 years, as it caused a massive migration of species to new areas, and consequently contact between species which do not normally come in contact with one another. Even in a scenario with weak climatic changes, there will be 15,000 spillover of viruses to new hosts in the next decades. The areas with the most possibilities for spillover are the mountainous tropical regions of Africa and southeast Asia. Southeast Asia is especially vulnerable as it has a large number of bat species that generally do not mix, but could easily if climate change forced them to begin migrating.<ref>{{cite news |last1=Yong |first1=Ed |title=We Created the 'Pandemicene' |url=https://www.theatlantic.com/science/archive/2022/04/how-climate-change-impacts-pandemics/629699/ |access-date=6 May 2022 |agency=The Atlantic |date=28 April 2022}}</ref>

A 2021 study found possible links between climate change and transmission of COVID-19 through bats. The authors suggest that climate-driven changes in the distribution and robustness of bat species harboring coronaviruses may have occurred in eastern Asian hotspots (southern China, Myanmar, and Laos), constituting a driver behind the evolution and spread of the virus.<ref>{{cite journal | vauthors = Beyer RM, Manica A, Mora C | title = Shifts in global bat diversity suggest a possible role of climate change in the emergence of SARS-CoV-1 and SARS-CoV-2 | journal = The Science of the Total Environment | volume = 767 | article-number = 145413 | date = May 2021 | pmid = 33558040 | pmc = 7837611 | doi = 10.1016/j.scitotenv.2021.145413 | bibcode = 2021ScTEn.76745413B | doi-access = free }}</ref><ref>{{cite web| vauthors = Bressan D |title=Climate Change Could Have Played A Role In The Covid-19 Outbreak|url=https://www.forbes.com/sites/davidbressan/2021/02/08/climate-change-could-have-played-a-role-in-the-covid-19-outbreak/|access-date=9 February 2021|website=Forbes}}</ref>

===Secondary transmission ===
Zoonotic diseases contribute significantly to the burdened public health system as vulnerable groups such the elderly, children, childbearing women and immune-compromised individuals are at risk.{{citation needed|date=August 2024}} According to the [[World Health Organization]] (WHO), any disease or infection that is primarily "naturally" transmissible from vertebrate animals to humans or from humans to animals is classified as a zoonosis.<ref name=":0">{{Cite journal |last1=Rahman |first1=Md Tanvir |last2=Sobur |first2=Md Abdus |last3=Islam |first3=Md Saiful |last4=Ievy |first4=Samina |last5=Hossain |first5=Md Jannat |last6=El Zowalaty |first6=Mohamed E. |last7=Rahman |first7=AMM Taufiquer |last8=Ashour |first8=Hossam M. |date=September 2020 |title=Zoonotic Diseases: Etiology, Impact, and Control |journal=Microorganisms |language=en |volume=8 |issue=9 |page=1405 |doi=10.3390/microorganisms8091405 |doi-access=free |issn=2076-2607 |pmc=7563794 |pmid=32932606}}</ref> Factors such as climate change, urbanization, animal migration and trade, travel and tourism, vector biology, anthropogenic factors, and natural factors have greatly influenced the emergence, re-emergence, distribution, and patterns of zoonoses.<ref name=":0" />

Zoonotic diseases generally refer to diseases of animal origin in which direct or vector mediated animal-to-human transmission is the usual source of human infection. Animal populations are the principal reservoir of the pathogen and horizontal infection in humans is rare. A few examples in this category include [[lyssavirus]] infections, [[Lyme disease|Lyme borreliosis]], plague, tularemia, [[leptospirosis]], [[ehrlichiosis]], [[Nipah virus infection|Nipah virus]], [[West Nile virus]], and [[hantavirus]] infections.<ref name=":1">{{Cite journal |last1=SCHLUNDT |first1=J. |last2=TOYOFUKU |first2=H. |last3=FISHER |first3=J.R. |last4=ARTOIS |first4=M. |last5=MORNER |first5=T. |last6=TATE |first6=C.M. |date=2004-08-01 |title=The role of wildlife in emerging and re-emerging zoonoses |journal=Revue Scientifique et Technique de l'OIE |volume=23 |issue=2 |pages=485–496 |doi=10.20506/rst.23.2.1498 |issn=0253-1933}}</ref> Secondary transmission encompasses a category of diseases of animal origin in which the actual transmission to humans is a rare event but, once it has occurred, human-to-human transmission maintains the infection cycle for some period of time. Some examples include [[HIV|human immunodeficiency virus (HIV)]]/acquired immune deficiency syndrome (AIDS), certain influenza A strains, [[Ebola]] virus and [[severe acute respiratory syndrome]] (SARS).<ref name=":1" />

One example is [[Ebola]], which is spread by direct transmission to humans from handling [[bushmeat]] (wild animals hunted for food) and contact with infected bats or close contact with infected animals, including chimpanzees, fruit bats, and forest antelope. Secondary transmission also occurs from [[Human-to-human transmission|human to human]] by direct contact with blood, bodily fluids, or skin of patients with or who died of Ebola virus disease.<ref>{{Cite journal |last1=Rewar |first1=Suresh |last2=Mirdha |first2=Dashrath |date=2015-05-08 |title=Transmission of Ebola Virus Disease: An Overview |journal=Annals of Global Health |language=en-US |volume=80 |issue=6 |pages=444–451 |doi=10.1016/j.aogh.2015.02.005 |pmid=25960093 |issn=2214-9996|doi-access=free }}</ref> Some examples of pathogens with this pattern of secondary transmission are human immunodeficiency virus/acquired immune deficiency syndrome, influenza A, Ebola virus, and SARS. Recent infections of these [[Emerging infectious disease|emerging]] and re-emerging zoonotic infections have occurred as a results of many ecological and sociological changes globally.<ref name=":1" />

== History ==
During most of human [[prehistory]] groups of [[hunter-gatherers]] were probably very small. Such groups probably made contact with other such bands only rarely. Such isolation would have caused epidemic diseases to be restricted to any given local population, because propagation and expansion of epidemics depend on frequent contact with other individuals who have not yet developed an adequate [[immune response]].<ref>{{cite web |title=Early Concepts of Disease |url=https://sphweb.bumc.bu.edu/otlt/mph-modules/ep/ep713_history/ep713_history2.html |access-date=22 April 2022 |website=sphweb.bumc.bu.edu}}</ref> To persist in such a population, a pathogen either had to be a [[chronic (medicine)|chronic]] infection, staying present and potentially infectious in the infected host for long periods, or it had to have other additional species as [[natural reservoir|reservoir]] where it can maintain itself until further susceptible hosts are contacted and infected.<ref>{{cite book |last1=Van Seventer |first1=Jean Maguire |last2=Hochberg |first2=Natasha S. |date=2017 |chapter=Principles of Infectious Diseases:Transmission, Diagnosis, Prevention, and Control |title=International Encyclopedia of Public Health |pages=22–39 |doi=10.1016/B978-0-12-803678-5.00516-6 |pmc=7150340|isbn=978-0-12-803708-9 }}</ref><ref>{{cite book |last1=Health (US) |first1=National Institutes of |url=https://www.ncbi.nlm.nih.gov/books/NBK20370/ |title=Understanding Emerging and Re-emerging Infectious Diseases |last2=Study |first2=Biological Sciences Curriculum |date=2007 |publisher=National Institutes of Health (US) }}</ref> In fact, for many "human" diseases, the human is actually better viewed as an accidental or incidental victim and a [[dead-end host]]. Examples include rabies, anthrax, tularemia, and West Nile fever. Thus, much of human exposure to infectious disease has been zoonotic.<ref>{{cite journal |last=Baum |first=Stephen G. |date=2008 |title=Zoonoses-With Friends Like This, Who Needs Enemies? |journal=Transactions of the American Clinical and Climatological Association |volume=119 |pages=39–52 |issn=0065-7778 |pmc=2394705 |pmid=18596867}}</ref>
[[File:Figure 3- Examples of Zoonotic Diseases and Their Affected Populations (6323431516).jpg|thumb|Possibilities for zoonotic disease transmissions]]

Many diseases, even epidemic ones, have zoonotic origin and [[measles]], [[smallpox]], [[influenza]], HIV, and [[diphtheria]] are particular examples.<ref>{{cite journal |last1=Weiss |first1=Robin A |last2=Sankaran |first2=Neeraja |date=18 January 2022 |title=Emergence of epidemic diseases: zoonoses and other origins |journal=Faculty Reviews |volume=11 |page=2 |doi=10.12703/r/11-2 |issn=2732-432X |pmc=8808746 |pmid=35156099 |doi-access=free }}</ref><ref>{{cite journal |last1=Wolfe |first1=Nathan D. |last2=Dunavan |first2=Claire Panosian |last3=Diamond |first3=Jared |date=May 2007 |title=Origins of major human infectious diseases |journal=Nature |volume=447 |issue=7142 |pages=279–283 |doi=10.1038/nature05775 |pmid=17507975 |pmc=7095142 |bibcode=2007Natur.447..279W |issn=1476-4687}}</ref> Various forms of the [[common cold]] and [[tuberculosis]] also are adaptations of strains originating in other species.<ref>{{Cite web |title=Common Cold Virus Came From Birds About 200 Years Ago, Study Suggests |url=https://www.sciencedaily.com/releases/2008/11/081120073115.htm |access-date=2025-02-10 |website=ScienceDaily |language=en}}</ref><ref>{{Cite journal |last1=Holloway |first1=K.L. |last2=Henneberg |first2=R.J. |last3=de Barros Lopes |first3=M. |last4=Henneberg |first4=M. |date=December 2011 |title=Evolution of human tuberculosis: A systematic review and meta-analysis of paleopathological evidence |journal=Homo |volume=62 |issue=6 |pages=402–458 |doi=10.1016/j.jchb.2011.10.001 |pmid=22093291 |issn=0018-442X}}</ref> Some experts have suggested that all human viral infections were originally zoonotic.<ref>{{cite journal | vauthors = Benatar D | title = The chickens come home to roost | journal = American Journal of Public Health | volume = 97 | issue = 9 | pages = 1545–1546 | date = September 2007 | pmid = 17666704 | pmc = 1963309 | doi = 10.2105/AJPH.2006.090431 | author-link = David Benatar }}</ref>

Zoonoses are of interest because they are often previously unrecognized diseases or have increased virulence in populations lacking immunity. The West Nile virus [[West Nile virus in the United States#Discovery in the United States|first appeared in the United States in 1999]], in the New York City area. [[Bubonic plague]] is a zoonotic disease,<ref>{{cite journal | vauthors = Meerburg BG, Singleton GR, Kijlstra A | title = Rodent-borne diseases and their risks for public health | journal = Critical Reviews in Microbiology | volume = 35 | issue = 3 | pages = 221–270 | year = 2009 | pmid = 19548807 | doi = 10.1080/10408410902989837 | s2cid = 205694138 }}</ref> as are [[salmonellosis]], [[Rocky Mountain spotted fever]], and [[Lyme disease]].

A major factor contributing to the appearance of new zoonotic pathogens in human populations is increased contact between humans and wildlife.<ref>{{cite journal | vauthors = Daszak P, Cunningham AA, Hyatt AD | title = Anthropogenic environmental change and the emergence of infectious diseases in wildlife | journal = Acta Tropica | volume = 78 | issue = 2 | pages = 103–116 | date = February 2001 | pmid = 11230820 | doi = 10.1016/S0001-706X(00)00179-0 }}</ref> This can be caused either by encroachment of human activity into wilderness areas or by movement of wild animals into areas of human activity. An example of this is the outbreak of [[Henipavirus#Nipah virus|Nipah virus]] in peninsular Malaysia, in 1999, when [[intensive pig farming]] began within the habitat of infected fruit bats.<ref>{{cite journal |last1=Looi |first1=Lai-Meng |last2=Chua |first2=Kaw-Bing |title=Lessons from the Nipah virus outbreak in Malaysia |journal=Malaysian Journal of Pathology |date=2007 |volume=29 |issue=2 |pages=63–67 |pmid=19108397}}</ref> The unidentified infection of these pigs amplified the force of infection, transmitting the virus to farmers, and eventually causing 105 human deaths.<ref>{{cite journal | vauthors = Field H, Young P, Yob JM, Mills J, Hall L, Mackenzie J | title = The natural history of Hendra and Nipah viruses | journal = Microbes and Infection | volume = 3 | issue = 4 | pages = 307–314 | date = April 2001 | pmid = 11334748 | doi = 10.1016/S1286-4579(01)01384-3 }}</ref>

Similarly, in recent times avian influenza and West Nile virus have [[Spillover infection|spilled over]] into human populations probably due to interactions between the carrier host and domestic animals.<ref>{{Citation |last=Fong |first=I. W. |title=Animals and Mechanisms of Disease Transmission |date=2017 |journal=Emerging Zoonoses |pages=15–38 |place=Cham |publisher=Springer International Publishing |doi=10.1007/978-3-319-50890-0_2 |pmc=7120673 |isbn=978-3-319-50888-7}}</ref> Highly mobile animals, such as bats and birds, may present a greater risk of zoonotic transmission than other animals due to the ease with which they can move into areas of human habitation.

Because they depend on the human host<ref>{{cite web |last=Basu |first=Dr Muktisadhan |date=16 August 2022 |title=Zoonotic Diseases and Its Impact on Human Health |url=https://agritechconsultancyservices.com/zoonotic-diseases-and-its-impact-on-human-health/ |access-date=25 March 2023 |website=Agritech Consultancy Services |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325105343/https://agritechconsultancyservices.com/zoonotic-diseases-and-its-impact-on-human-health/ }}</ref> for part of their life-cycle, diseases such as African [[schistosomiasis]], [[river blindness]], and [[Lymphatic filariasis|elephantiasis]] are ''not'' defined as zoonotic, even though they may depend on transmission by insects or other [[Vector (epidemiology)|vectors]].{{citation needed|date=September 2021}}

== Use in vaccines ==
The first vaccine against smallpox by [[Edward Jenner]] in 1800 was by infection of a zoonotic bovine virus which caused a disease called [[cowpox]].<ref>{{cite web|date=21 February 2021|title=History of Smallpox {{!}} Smallpox {{!}} CDC|url=https://www.cdc.gov/smallpox/history/history.html|access-date=21 September 2021|website=www.cdc.gov|archive-date=14 June 2020|archive-url=https://web.archive.org/web/20200614213232/https://www.cdc.gov/smallpox/history/history.html|url-status=live}}</ref> Jenner had noticed that [[milkmaid]]s were resistant to smallpox. Milkmaids contracted a milder version of the disease from infected cows that conferred cross immunity to the human disease. Jenner abstracted an infectious preparation of 'cowpox' and subsequently used it to inoculate persons against smallpox. As a result of vaccination, smallpox has been eradicated globally, and mass inoculation against this disease ceased in 1981.<ref>{{cite web|url=https://www.cdc.gov/smallpox/history/smallpox-origin.html|title=The Spread and Eradication of Smallpox &#124; Smallpox &#124; CDC|date=19 February 2019}}</ref> There are a variety of vaccine types, including traditional inactivated pathogen vaccines, [[subunit vaccine]]s, [[Attenuated vaccine|live attenuated vaccines]]. There are also new vaccine technologies such as viral vector vaccines and [[MRNA vaccine|DNA/RNA vaccines]], which include many of the [[COVID-19 vaccine]]s.<ref>{{Cite web |last=Mayo Clinic Staff |date=4 November 2023 |title=Different types of COVID-19 vaccines: How they work |url=https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/different-types-of-covid-19-vaccines/art-20506465 |access-date=4 April 2024 |website=Mayo Clinic}}</ref>

== Lists of diseases ==
{{Main|List of zoonotic diseases}}

== See also ==
{{col div|colwidth=30em}}
* {{annotated link|Animal welfare#Animal welfare organizations}}
* {{annotated link|Conservation medicine}}
* {{annotated link|Cross-species transmission}}
* {{annotated link|Emerging infectious disease}}
* {{annotated link|Foodborne illness}}
* {{annotated link|Spillover infection}}
* {{annotated link|Wildlife disease}}
* {{annotated link|Veterinary medicine}}
* {{annotated link|Wildlife smuggling and zoonoses}}
* {{annotated link|List of zoonotic primate viruses}}
{{colend}}

== References ==
{{Reflist}}

== Bibliography ==
{{Refbegin}}
* {{cite book | vauthors = Bardosh K | title = One Health: Science, Politics and Zoonotic Disease in Africa | date = 2016 | publisher = Routledge | location = London | isbn = 978-1-138-96148-7}}.
* {{cite book | vauthors = Crawford D |date=2018 |title=Deadly Companions: How Microbes Shaped our History |publisher=Oxford University Press | isbn=978-0-19-881544-0 }}
* {{cite web |url=https://www.brookings.edu/articles/preventing-the-next-zoonotic-pandemic/ |title=Preventing the next zoonotic pandemic | vauthors = Felbab-Brown V |date=6 October 2020 |website=Brookings Institution |access-date=19 January 2021 |archive-date=21 January 2021 |archive-url=https://web.archive.org/web/20210121122104/https://www.brookings.edu/articles/preventing-the-next-zoonotic-pandemic/ |url-status=live }}
* {{cite journal | vauthors = Greger M | title = The human/animal interface: emergence and resurgence of zoonotic infectious diseases | journal = Critical Reviews in Microbiology | volume = 33 | issue = 4 | pages = 243–299 | date = 2007 | pmid = 18033595 | doi = 10.1080/10408410701647594 | url = https://animalstudiesrepository.org/cgi/viewcontent.cgi?article=1002&context=acwp_tzd | access-date = 29 September 2020 | url-status = live | s2cid = 8940310 | archive-url = https://web.archive.org/web/20200801195425/https://animalstudiesrepository.org/cgi/viewcontent.cgi?article=1002&context=acwp_tzd | archive-date = 1 August 2020 | url-access = subscription }}
* H. Krauss, A. Weber, M. Appel, B. Enders, A. v. Graevenitz, H. D. Isenberg, H. G. Schiefer, W. Slenczka, H. Zahner: Zoonoses. Infectious Diseases Transmissible from Animals to Humans. 3rd Edition, 456 pages. ASM Press. American Society for Microbiology, Washington, D.C., 2003. {{ISBN|1-55581-236-8}}.
* {{cite book | vauthors = González JG |title=Infection Risk and Limitation of Fundamental Rights by Animal-To-Human Transplantations. EU, Spanish and German Law with Special Consideration of English Law |publisher=Verlag Dr. Kovac|location=Hamburg|year=2010|isbn=978-3-8300-4712-4|language=de}}
* {{cite book|title=[[Spillover: Animal Infections and the Next Human Pandemic]]| vauthors = Quammen D |year=2013| publisher = W. W. Norton & Company |isbn=978-0-393-34661-9}}
{{Refend}}

== External links ==
{{Medical resources
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{{Commons category|Zoonoses}}
{{Wiktionary}}
{{Scholia|topic}}
* [https://web.archive.org/web/20120205080642/http://www.avma.org/avmacollections/zu/default.asp AVMA Collections: Zoonosis Updates]
* [http://www.emro.who.int/entity/zoonoses/ WHO tropical diseases and zoonoses]
* [https://inlportal.inl.gov/portal/server.pt/community/idaho_national_laboratory_biological_systems/352/molecular_forensics/2691 Detection and Forensic Analysis of Wildlife and Zoonotic Disease]
* [http://digitalcommons.unl.edu/zoonoticspub/ Publications in Zoonotics and Wildlife Disease]
* [https://www.unenvironment.org/news-and-stories/video/message-nature-coronavirus  A message from nature: coronavirus]. [[United Nations Environment Programme]]
* [https://vbdhub.org UK's ''One Health Vector-Borne Diseases Hub'']

{{Zoonotic viral diseases}}
{{Tick-borne diseases}}
{{Concepts in infectious disease}}

{{Authority control}}

[[Category:Zoonoses| ]]
[[Category:Animal diseases]]
[[Category:Disease ecology]]
[[Category:Infectious diseases]]