it has a large number of bat species that generally do not mix, but could easily if climate change forced them to begin migrating. 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. secondary transmission ebola and marburg are examples of viral hemorrhagic disease. 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. to persist in such a population, a pathogen either had to be a chronic infection, staying present and potentially infectious in the infected host for long periods, or it had to have other additional species as reservoir where it can maintain itself until further susceptible hosts are contacted and infected. 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 virus. thus, much of human exposure to infectious disease has been zoonotic. possibilities for zoonotic disease transmissions many diseases, even epidemic ones, have zoonotic origin and measles, smallpox, influenza, hiv, and diphtheria are particular examples. various forms of the common cold and tuberculosis also are adaptations of strains originating in other species. some experts have suggested that all human viral infections were originally zoonotic. zoonoses are of interest because they are often previously unrecognized diseases or have increased virulence in populations lacking immunity. the west nile virus first appeared in the united states in 1999, in the new york city area. bubonic plague is a zoonotic disease, 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. 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 nipah virus in peninsular malaysia, in 1999, when intensive pig farming began within the habitat of infected fruit bats. the unidentified infection of these pigs amplified the force of infection, transmitting the virus to farmers, and eventually causing 105 human deaths. similarly, in recent times avian influenza and west nile virus have spilled over into human populations probably due to interactions between the carrier host and domestic animals. 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 for part of their life-cycle, diseases such as african schistosomiasis, river blindness, and elephantiasis are not defined as zoonotic, even though they may depend on transmission by insects or other vectors. 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. jenner had noticed that milkmaids 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, smallpox has been eradicated globally, and mass vaccination against this disease ceased in 1981. there are a variety of vaccine varieties, including traditional inactivated pathogen vaccines, subunit vaccines, live attenuated vaccines. there are also new vaccine technologies such as viral vector vaccines and dna/rna vaccines, which includes the sars-cov-2 coronavirus vaccines. lists of diseases disease pathogen(s) animals involved mode of transmission emergence african sleeping sickness trypanosoma brucei rhodesiense range of wild animals and domestic livestock transmitted by the bite of the tsetse fly 'present in africa for thousands of years' – major outbreak 1900–1920, cases continue (sub-saharan africa, 2020) angiostrongyliasis angiostrongylus cantonensis, angiostrongylus costaricensis rats, cotton rats consuming raw or undercooked snails, slugs, other mollusks, crustaceans, contaminated water, and unwashed vegetables contaminated with larvae anisakiasis anisakis whales, dolphins, seals, sea lions, other marine animals eating raw or undercooked fish and squid contaminated with eggs anthrax bacillus anthracis commonly – grazing herbivores such as cattle, sheep, goats, camels, horses, and pigs by ingestion, inhalation or skin contact of spores babesiosis babesia spp. mice, other animals tick bite baylisascariasis baylisascaris procyonis raccoons ingestion of eggs in feces barmah forest fever barmah forest virus kangaroos, wallabies, opossums mosquito bite bird flu influenza a virus subtype h5n1 wild birds, domesticated birds such as chickens close contact 2003–19 avian influenza in southeast asia and egypt bovine spongiform encephalopathy prions cattle eating infected meat isolated similar cases reported in ancient history; in recent uk history probable start in the 1970s brucellosis brucella spp. cattle, goats, pigs, sheep infected milk or meat historically widespread in mediterranean region; identified early 20th century bubonic plague, pneumonic plague, septicemic plague, sylvatic plague yersinia pestis rabbits, hares, rodents, ferrets, goats, sheep, camels flea bite epidemics like black death in europe around 1347–53 during the late middle age, third plague pandemic in china-qing dynasty and india alone capillariasis capillaria spp. rodents, birds, foxes eating raw or undercooked fish, ingesting embryonated eggs in fecal-contaminated food, water, or soil cat-scratch disease bartonella henselae cats bites or scratches from infected cats chagas disease trypanosoma cruzi armadillos, triatominae (kissing bug) contact of mucosae or wounds with feces of kissing bugs. accidental ingestion of parasites in food contaminated by bugs or infected mammal excretae. clamydiosis / enzootic abortion chlamydophila abortus domestic livestock, particularly sheep close contact with postpartum ewes suspected: covid-19 severe acute respiratory syndrome coronavirus 2 suspected: bats, felines, raccoon dogs, minks. white-tailed deer respiratory transmission covid-19 pandemic; 2019–present; ongoing pandemic creutzfeldt-jacob disease prpvcjd cattle eating meat from animals with bovine spongiform encephalopathy (bse) 1996–2001: united kingdom crimean–congo hemorrhagic fever crimean-congo hemorrhagic fever orthonairovirus cattle, goats, sheep, birds, multimammate rats, hares tick bite, contact with bodily fluids cryptococcosis cryptococcus neoformans commonly – birds like pigeons inhaling fungi cryptosporidiosis cryptosporidium spp. cattle, dogs, cats, mice, pigs, horses, deer, sheep, goats, rabbits, leopard geckos, birds ingesting cysts from water contaminated with feces cysticercosis and taeniasis taenia solium, taenia asiatica, taenia saginata commonly – pigs and cattle consuming water, soil or food contaminated with the tapeworm eggs (cysticercosis) or raw or undercooked pork contaminated with the cysticerci (taeniasis) dirofilariasis dirofilaria spp. dogs, wolves, coyotes, foxes, jackals, cats, monkeys, raccoons, bears, muskrats, rabbits, leopards, seals, sea lions, beavers, ferrets, reptiles mosquito bite eastern equine encephalitis, venezuelan equine encephalitis, western equine encephalitis eastern equine encephalitis virus, venezuelan equine encephalitis virus, western equine encephalitis virus horses, donkeys, zebras, birds mosquito bite ebola virus disease (a haemorrhagic fever) ebolavirus spp. chimpanzees, gorillas, orangutans, fruit bats, monkeys, shrews, forest antelope and porcupines through body fluids and organs 2013–16; possible in africa other haemorrhagic fevers (crimean-congo haemorrhagic fever, dengue fever, lassa fever, marburg viral haemorrhagic fever, rift valley fever) varies – commonly viruses varies (sometimes unknown) – commonly camels, rabbits, hares, hedgehogs, cattle, sheep, goats, horses and swine infection usually occurs through direct contact with infected animals 2019–20 dengue fever echinococcosis echinococcus spp. commonly – dogs, foxes, jackals, wolves, coyotes, sheep, pigs, rodents ingestion of infective eggs from contaminated food or water with feces of an infected definitive host fasciolosis fasciola hepatica, fasciola gigantica sheep, cattle, buffaloes ingesting contaminated plants fasciolopsiasis fasciolopsis buski pigs eating raw vegetables such as water spinach foodborne illnesses (commonly diarrheal diseases) campylobacter spp., escherichia coli, salmonella spp., listeria spp., shigella spp. and trichinella spp. animals domesticated for food production (cattle, poultry) raw or undercooked food made from animals and unwashed vegetables contaminated with feces giardiasis giardia lamblia beavers, other rodents, raccoons, deer, cattle, goats, sheep, dogs, cats ingesting spores and cysts in food and water contaminated with feces glanders burkholderia mallei. horses, donkeys direct contact gnathostomiasis gnathostoma spp. dogs, minks, opossums, cats, lions, tigers, leopards, raccoons, poultry, other birds, frogs raw or undercooked fish or meat hantavirus hantavirus spp. deer mice, cotton rats and other rodents exposure to feces, urine, saliva or bodily fluids henipavirus henipavirus spp. horses, bats exposure to feces, urine, saliva or contact with sick horses hepatitis e hepatitis e virus domestic and wild animals contaminated food or water histoplasmosis histoplasma capsulatum birds, bats inhaling fungi in guano hiv siv simian immunodeficiency virus non-human primates blood immunodeficiency resembling human aids was reported in captive monkeys in the united states beginning in 1983. siv was isolated in 1985 from some of these animals, captive rhesus macaques who had simian aids (saids). the discovery of siv was made shortly after hiv-1 had been isolated as the cause of aids and led to the discovery of hiv-2 strains in west africa. hiv-2 was more similar to the then-known siv strains than to hiv-1, suggesting for the first time the simian origin of hiv. further studies indicated that hiv-2 is derived from the sivsmm strain found in sooty mangabeys, whereas hiv-1, the predominant virus found in humans, is derived from siv strains infecting chimpanzees (sivcpz) japanese encephalitis japanese encephalitis virus pigs, water birds mosquito bite kyasanur forest disease kyasanur forest disease virus rodents, shrews, bats, monkeys tick bite la crosse encephalitis la crosse virus chipmunks, tree squirrels mosquito bite leishmaniasis leishmania spp. dogs, rodents, other animals sandfly bite 2004 afghanistan leprosy mycobacterium leprae, mycobacterium lepromatosis armadillos, monkeys, rabbits, mice direct contact, including meat consumption. however, scientists believe most infections are spread human to human. leptospirosis leptospira interrogans rats, mice, pigs, horses, goats, sheep, cattle, buffaloes, opossums, raccoons, mongooses, foxes, dogs direct or indirect contact with urine of infected animals 1616–20 new england infection: present day in the united states) lassa fever lassa fever virus rodents exposure to rodents lyme disease borrelia burgdorferi deer, wolves, dogs, birds, rodents, rabbits, hares, reptiles tick bite lymphocytic choriomeningitis lymphocytic choriomeningitis virus rodents exposure to urine, feces, or saliva melioidosis burkholderia pseudomallei various animals direct contact with contaminated soil and surface water microsporidiosis encephalitozoon cuniculi rabbits, dogs, mice, and other mammals ingestion of spores middle east respiratory syndrome mers coronavirus bats, camels close contact 2012–present: saudi arabia monkeypox monkeypox virus rodents, primates contact with infected rodents, primates, or contaminated materials nipah virus infection nipah virus (niv) bats, pigs direct contact with infected bats, infected pigs orf orf virus goats, sheep close contact powassan encephalitis powassan virus ticks tick bites psittacosis chlamydophila psittaci macaws, cockatiels, budgerigars, pigeons, sparrows, ducks, hens, gulls and many other bird species contact with bird droplets q fever coxiella burnetii livestock and other domestic animals such as dogs and cats inhalation of spores, contact with bodily fluid or faeces rabies rabies virus commonly – dogs, bats, monkeys, raccoons, foxes, skunks, cattle, goats, sheep, wolves, coyotes, groundhogs, horses, mongooses and cats through saliva by biting, or through scratches from an infected animal variety of places like oceanic, south america, europe; year is unknown rat-bite fever streptobacillus moniliformis, spirillum minus rats, mice bites of rats but also urine and mucus secretions rift valley fever phlebovirus livestock, buffaloes, camels mosquito bite, contact with bodily fluids, blood, tissues, breathing around butchered animals or raw milk 2006–07 east africa outbreak rocky mountain spotted fever rickettsia rickettsii dogs, rodents tick bite ross river fever ross river virus kangaroos, wallabies, horses, opossums, birds, flying foxes mosquito bite saint louis encephalitis saint louis encephalitis virus birds mosquito bite severe acute respiratory syndrome sars coronavirus bats, civets close contact, respiratory droplets 2002–04 sars outbreak; started in china smallpox variola virus possible monkeys or horses spread to person to person quickly the last cases was in 1977; who certified to eradicated (for the world) in december 1979 or 1980. swine influenza a new strain of the influenza virus endemic in pigs (excludes h1n1 swine flu, which is a human virus). pigs close contact 2009–10; 2009 swine flu pandemic; the outbreak began in mexico. taenia crassiceps infection taenia crassiceps wolves, coyotes, jackals, foxes contact with soil contaminated with feces