Viral Diseases

Alkhurma (Alkhumra) hemorrhagic fever

Alkhurma (=Alkhumra) virus (family Flaviviirdae, genus Flavivirus); variant of Kyasanur Forest virus; member of tickborne encephalitis virus serocomplex

Sheep, goats, camels

Middle East

Ticks (Ornithodoros and Hyalomma spp); direct contact with animal meat via broken skin or ingestion of unpasteurized camel milk linked to some cases

Febrile illness, often with GI signs; encephalitic/neurologic and hemorrhagic signs in some; early reports suggested case fatality up to 25% but probably lower, recently < 1%; subclinical infections may be common

Barmah Forest virus infection; epidemic polyarthritis

Barmah Forest virus (family Togaviridae, genus Alphavirus)

Natural hosts unknown; horses, brushtail possums, kangaroos might hosts

Australia, Papua New Guinea

Mosquito bites; Culex and Aedes spp implicated; also found in Culicoides midges

Resembles disease due to Ross River virus; fever, rash, and nonspecific clinical signs; myalgia and polyarthralgia can persist for months

Buffalopox

Vaccinia virus, Buffalopox virus strain (family Poxviridae, genus Orthopoxvirus)

Water buffalo, cattle

Indian subcontinent (south Asia), Indonesia, parts of Middle East

Skin contact with infected animals, often when milking

Pox skin lesions mainly on hands, face, legs, buttocks; occasionally lymphadenopathy, fever, malaise

California encephalitis virus serogroup (California serogroup) infections

California encephalitis virus serogroup (family Bunyaviridae, genus Orthobunyavirus); includes California, La Crosse, Tahyna, Inkoo, Jamestown Canyon, Morro Bay, Snowshoe hare, Guaroa, Lumbo, Chatanga, and other viruses

Many wild and domestic mammals; major reservoirs and amplifying hosts can differ between viruses

North and South America, Europe, Africa, Asia; possibly worldwide; distribution of each virus varies

Mosquito bites

Syndromes, severity vary with the virus; flu-like illness, meningitis, or encephalitis common with North American viruses

—La Crosse encephalitis

La Crosse virus (California encephalitis virus serogroup)

Chipmunks, squirrels are major amplifying hosts; other mammals can be infected

North America

Mosquito bites

Many cases mild and flu-like; meningitis or encephalitis with seizures, paralysis, and focal neurologic signs possible; most cases in children; estimated case fatality rate < 1% in cases with encephalitis

—Tahyna fever

Tahyna virus (California encephalitis virus serogroup)

Hares, rabbits, rodents, hedgehogs, and other mammals

Europe, Asia, Africa

Mosquito bites (culicine and anopheles)

Influenza-like illness, sometimes including GI signs; arthritis or respiratory signs, including bronchopneumonia in some; meningitis possible but appears uncommon; most often in children; does not appear to cause fatal disease

Camelpox

Camelpox virus

Old World camelids, possibly other species

Middle East, Asia, Africa, possibly other areas; human cases recently described in India in camel handlers, rare unconfirmed cases suggested in other locations

Direct contact

Skin lesions similar to cowpox, variola virus infections

Chikungunya

Chikungunya virus (family Togaviridae, genus Alphavirus)

Sylvatic cycle in nonhuman primates, possibly rodents in Africa; Asian lineage virus thought to be maintained in humans; however, sylvatic cycle may also exist in some locations

Asia, Africa, Europe, South America

Mosquito bites (especially Aedes spp)

Febrile illness, may have rash and/or GI signs; arthralgia, especially in small joints, and myalgia prominent, may persist for months; myocarditis, neurologic signs, hemorrhages reported in a few cases

Colorado tick fever

Colorado tick fever virus (family Reoviridae, genus Coltivurus; Salmon River virus and California hare coltivirus may be variants

Rodents and small mammals and other mammals can also be infected

Some regions in western North America

Tick bites (primary vector is Dermacentor andersoni)

Nonspecific febrile illness; pharyngitis, rash, or GI signs possible; biphasic or triphasic in some; complications (eg, neurologic signs, hemorrhages, pericarditis, myocarditis, orchitis) uncommon but can occur in severe cases; deaths rare

Contagious ecthyma

Orf virus (family Poxviridae, genus Parapoxvirus)

Sheep, goats, camelids, wild ungulates; rare cases in dogs and cats

Worldwide

Occupational exposure via contact with broken skin (both live animals and meat processing)

Papule(s) that umbilicate and ulcerate, usually on hands; dissemination rare but has occurred in humans with atopic dermatitis; large lesions refractory to treatment can occur in immunosuppressed

Cowpox

Cowpox virus (family Poxviridae, genus Orthopoxvirus)

Rodents are usual reservoir host; also in domestic and wild cats, occasionally cattle, other mammals

Parts of Europe and Asia

Contact exposure via broken skin, bites, scratches

Papules, vesicles that become pustular, to ulcerative nodules, scars; single or multiple lesions, often on hands; regional adenopathy and malaise, flu-like symptoms in some; lesions remain localized in healthy humans; more extensive or generalized disease may occur in children, humans with eczema, immunocompromised; severe cases can involve respiratory mucosa; rare fatal cases (eg, complications of encephalitis)

Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever virus (family Bunyaviridae, genus Orthonairovirus)

Cattle, water buffalo, rodents, sheep, goats, hares, other mammals, rarely in birds (eg, ostriches)

Africa, Middle East, Asia, parts of Europe where Hyalomma ticks occur

Tick bites, especially Hyalomma but other genera may also transmit; skin, mucous membrane contact with blood or tissues of animals or crushed ticks; ingestion of unpasteurized milk and possibly uncooked animal tissues; rarely airborne; person-to-person transmission occurs, especially via hemorrhage and during close contact

Febrile flu-like signs, GI symptoms; hemorrhagic signs may begin with petechial rash; hepatitis, abortion, other organ involvement in some cases; asymptomatic or mild in some; case fatality rate usually 3%–30% but can be higher

Eastern equine encephalomyelitis

Eastern equine encephalomyelitis virus (EEEV), Madariaga virus (former South American EEEV lineages) (family Togaviridae, genus Alphavirus)

Birds are principal reservoir hosts, small mammals might also amplify, snakes might have role in overwintering virus; small mammals (eg, rodents), marsupials might be reservoir hosts for Madariaga virus; clinical cases in equids and occasionally other mammals and birds but domestic animals are almost always dead-end hosts

Americas

Mosquito bites; Culiseta melanura important in EEEV maintenance cycle; Culex spp might be important for Madariaga virus; various mosquito species (Aedes, Coquillettidia, Culex) can transmit to humans

EEEV causes nonspecific febrile illness, which may be followed by severe encephalitis; neurologic sequelae common after encephalitis; case fatality rate 30%–70%;more severe in infants and elderly; Madariaga virus causes similar signs but seems less severe

Ebola hemorrhagic fever

Zaire ebolavirus, Sudan ebolavirus, Tai Forest ebolavirus (formerly Ivory Coast ebolavirus), Bundibugyo ebolavirus (family Filoviridae, genus Ebolavirus); Reston ebolavirus does not seem to affect humans

Bats are reservoir hosts for Zaire ebolavirus and suspected reservoir hosts for others; primates, duikers, pigs, possibly other mammals can be infected

Africa

Contact with infected tissues (especially nonhuman primates and duikers), blood; probable transmission from bats in caves; person-to-person transmission occurs

Initially nonspecific febrile illness; maculopapular rash with desquamation; various oral/ pharyngeal mucosal lesions possible; signs of increased vascular permeability, mild to severe bleeding tendency, various other signs (eg, neurologic signs, dyspnea, multiorgan dysfunction) develop a few days after onset; mortality rate 36%–90%, varies with isolate

Encephalomyocarditis

Encephalomyocarditis virus (family Picornaviridae, genus Cardiovirus); implicated as zoonotic pathogen but few confirmed cases

Rodents, possibly wild boar, may be reservoir hosts; also found in wild and domestic mammals (including swine, nonhuman primates), and wild birds

Worldwide in animals

Probably ingestion of contaminated food or water

Nonspecific febrile illness, sometimes with GI signs, and/or decreased reflexes have been reported in adults, with recovery within several days; implicated in CNS signs, including paralysis in children; most infections may be asymptomatic or mild

Foot-and-mouth disease

Foot-and-mouth disease virus (family Picornaviridae, genus Aphthovirus, types A, O, C, SAT 1, SAT 2, SAT 3, and Asia 1)

Cattle, swine, sheep, goats, other cloven-hoofed animals (Artiodactyla), a few mammals in other orders

Asia, Africa, Middle East, South America

Contact exposure, typically in laboratories or other high concentrations of virus; broken skin or drinking virus-contaminated unpasteurized milk are recognized routes

Humans may become temporary nasal carriers after field exposure to virus but do not usually become ill; mild influenza-like disease and vesicular lesions (including lesions at site of skin entry) occur very rarely, mostly laboratory associated

Hantaviral diseases

—Hantaviral pulmonary syndrome

Sin Nombre, Black Creek Canal, Bayou, Andes, Choclo, Laguna Negra, and Cano Delgadito viruses, others (family Bunyaviridae, genus Hantavirus)

Reservoirs are rodents, insectivores; each virus tends to be associated with one to a few reservoir hosts; occasionally infect other hosts

North and South America

Aerosols from rodent excretions and secretions; contact with broken skin and mucous membranes; rodent bites; person-to-person transmission reported for Andes virus

Prodromal stage with nonspecific febrile illness; followed by respiratory failure, cardiac abnormalities; hemorrhagic signs possible, mainly with South American viruses; notable kidney disease uncommon; milder illnesses also possible; case fatality rate for most viruses approx. 25%–-40% in classical syndrome

—Hemorrhagic fever with renal syndrome

Hantaan, Dobrava-Belgrade, Puumala, Seoul, and Amur-Soochong viruses, others (family Bunyaviridae, genus Hantavirus)

Reservoirs are rodents, insectivores; each virus tends to be associated with one to a few reservoir hosts; occasionally infect other hosts

Europe, Asia, Africa; Seoul virus is worldwide

Aerosols from rodent excretions and secretions; contact with broken skin and mucous membranes; rodent bites

Prodromal stage with nonspecific febrile illness; followed by hypotension, renal signs to renal failure with oliguria; hemorrhagic signs, other syndromes (including respiratory) in some; milder illnesses also possible; case fatality rate varies from < 1% (Puumala virus) to 5% (Hantaan virus), and up to 10%–-15% in the past

Heartland virus disease

Heartland virus (family Bunyaviridae, genus Phlebovirus)

Not known

North America

Vector appears to be Amblyomma americanum tick

Febrile illness with headache, myalgia, arthralgia, diarrhea, thrombocytopenia; some cases fatal (may be associated with comorbidities)

Hendra virus infection

Hendra virus (family Paramyxoviridae, genus Henipavirus)

Fruit bats are normal reservoir host; horses can be infected

Australia

Direct contact with infected animals (all human cases have been linked with horses) or contaminated tissues

Respiratory infection, encephalitis (including recurrent encephalitis); few cases described but several were fatal

Hepatitis E

Hepatitis E virus, mammalian isolates (family Hepeviridae, genus Hepevirus); genotypes 3 and 6, possibly others, are zoonotic; genotypes 1 and 2 maintained in humans

Humans, swine, wild boar, deer, rabbits, ferrets, rats, mongoose, others; swine and probably other hosts are reservoirs for human infections

Worldwide; human and zoonotic genotypes may differ in prevalence between areas

Fecal-oral transmission; consumption of raw or undercooked meat and liver; waterborne, contact with animal reservoirs

Mild, self-limiting hepatitis to liver failure, more severe in pregnancy and can result in abortion, death of newborn, premature birth; usually acute, but can be chronic in organ-transplant patients; case fatality rate < 1% to 4% in general population, up to 20% in pregnant

Herpes B virus disease

Cercopithecine herpesvirus 1 (McHV, Herpesvirus simiae, B virus) (family Herpesviridae, genus Simplexvirus)

Carried in genus Macaca (Old World macaques), with lifelong latency and potential for periodic shedding after infection; other nonhuman primates susceptible; cell cultures

Worldwide, can be common, especially in closed groups of macaques; human cases rare

Monkey bites and scratches, contamination of mucous membranes with infected saliva, secretions

Influenza-like symptoms; vesicular skin lesions, pain, or itching around wound, followed by severe encephalitis with seizures, paralysis, coma; very high mortality rate in untreated cases

Influenza virus infections

—Avian influenza

Influenza A virus (family Orthomyxoviridae, genus Influenzavirus A); avian influenza viruses; many severe human cases linked to Asian lineage H5N1 highly pathogenic avian influenza (HPAI) or H7N9 LPAI viruses; however, other viruses also cause illness

Avian influenza viruses in wild and domestic birds, especially poultry; uncommon in mammals

Worldwide, distribution of strains varies

Usually by contact with infected poultry; avian viruses may be shed in respiratory secretions and feces

Avian influenza viruses can cause conjunctivitis, human influenza-like illness, or severe disease with multiorgan dysfunction, death; severity of disease varies with influenza strain

—Swine influenza

Influenza A virus (family Orthomyxoviridae, genus Influenzavirus A); swine influenza viruses

Usually in pigs; also turkeys; can infect mink, ferrets

Worldwide

Usually by contact with infected animals; swine influenza viruses occur in respiratory secretions

Seems to resemble human influenza; severity of disease varies; fatal cases have been reported uncommonly

Japanese encephalitis (Japanese B encephalitis)

Japanese encephalitis virus (family Flaviviridae, genus Flavivirus)

Swine, wild birds are important maintenance and amplifying hosts; horses ill but epidemiologically unimportant in amplification; other mammals, reptiles, amphibians may be infected, usually subclinically

Asia, parts of western Pacific islands and Australia

Mosquito bites especially Culex; Culex tritaeniorhynchus important in maintenance cycle; also through broken skin or mucous membranes after direct contact with infected tissues

Nonspecific febrile flu-like illness can progress to severe encephalitis or less common neurological syndromes (eg, flaccid paralysis) in some; neurologic sequelae very common in survivors of encephalitis; reported case fatality rates < 5%–40%

Kyasanur Forest disease

Kyasanur Forest virus (family Flaviviridae, genus Flavivirus); member of tickborne encephalitis virus serocomplex

Rodents, shrews, other small mammals, ground-feeding birds thought to be reservoirs; affects monkeys; possible infections in other mammals, birds

India

Tick bites (especially Haemaphysalis spp, also others)

Nonspecific febrile illness; characteristic papulovesicular eruption on upper soft palate in some; course may be biphasic; hemorrhagic signs (eg, ecchymoses, purpura, petechiae, GI bleeding, epistaxis) and/or neurologic signs possible in second stage; prolonged convalescence in many; case fatality rate ~3%

Lassa fever

Lassa virus (family Arenaviridae, genus Mammarenavirus)

Wild rodents, multimammate mouse is major host

West Africa

Contact with rodent excretions, secretions, or tissues; aerosols

Gradual onset of nonspecific febrile illness, may be followed by chest pain, cough, GI signs, hepatitis; severe swelling of head and neck, hypotension/shock can develop; pleural/pericardial effusions; hemorrhagic syndrome less common; overall mortality rate 1% in endemic areas; case fatality rate 15%–20% among hospitalized patients

Louping ill (Ovine encephalomyelitis)

Louping ill virus (family Flaviviridae, genus Flavivirus)

Sheep and red grouse are primary reservoirs; also reported in goats, South American camelids, cattle, horses, dogs, farmed cervids, other domestic and wild mammals; some birds related to grouse (eg, ptarmigan) are susceptible to experimental infection

UK, Northern Ireland; also reported in Norway, Denmark (island of Bornholm), part of eastern Russia; similar viruses in Spain, Greece, Turkey; historically in Bulgaria and possibly Japan

Usually tick bites (Ixodes ricinus) in animals but this route appears uncommon in humans; aerosol exposure in laboratory; contamination of skin wounds and mucous membranes after contact with cultures, infected animals or their tissues; possibly ingestion of milk; human illnesses seem to be rare and mostly laboratory associated

Biphasic influenza-like illness, sometimes followed by meningitis or meningoencephalitis, or polio-like paralytics, syndrome in second phase; case fatality rate appears low

Lymphocytic choriomeningitis

Lymphocytic choriomeningitis virus (family Arenaviridae, genus Mammarenavirus)

Reservoir mainly house mouse; can be maintained in some other mice, hamster populations; also infects guinea pigs, chinchillas, rats, nonhuman primates, some other mammals

Worldwide

Direct or indirect contact with host excretions and secretions (via mucous membranes, broken skin, aerosols); bites; possibly ingestion

Ranges from mild flu-like illness to biphasic with meningitis in second phase; complications (eg, arthritis of hands, parotitis, orchitis) possible; can cause congenital defects (CNS defects, chorioretinitis, and other ocular lesions) or abortion; rarely fatal in immunocompetent (overall case fatality rate < 1%); serious and life-threatening multisystemic disease in transplant patients

Marburg hemorrhagic fever

Marburg virus, Ravn virus (family Filoviridae, genus Marburgvirus)

Bats are reservoir hosts; primates can be infected

Africa

Contact with infected tissues (especially nonhuman primates); probable transmission from bats in caves

Initially nonspecific febrile illness; maculopapular rash with desquamation; hepatitis; signs of increased vascular permeability, mild to severe bleeding tendency, various organ dysfunctions develop a few days after onset; mortality rate 20%–88%, varies with isolate

Menangle virus infection

Menangle virus (family Paramyxoviridae)

Fruit bats are normal reservoir host; pigs can also be reservoir

Australia

Close direct contact with tissues, amniotic fluid or blood of pigs reported in human cases

Severe illness with fever, severe headache, myalgia, lymphadenopathy, drenching sweats, macular rash

Middle East respiratory syndrome (MERS)

MERS coronavirus

Dromedary camels source of virus for many cases in humans; bats might be a reservoir

Middle East; serologic evidence for virus in Africa

Contact with nasal secretions from camels; evidence for virus in unpasteurized camel milk, various tissues; possibly other virus sources

Asymptomatic or mild upper respiratory signs or flu-like illness to pneumonia; more severe in humans with coexisting illness or immunosuppression, elderly, but also in healthy; multiorgan failure possible; reported case fatality rates 20% or higher in confirmed cases but serologic evidence suggests milder cases probably missed

Milker’s nodules (pseudocowpox)

Pseudocowpox virus (family Poxviridae, genus Parapoxvirus)

Cattle

Worldwide

Skin contact (especially broken skin) with lesions on cow’s udder or mouth of calf; also from fomites

Papular to nodular red skin lesions; self-limiting

Monkeypox

Monkeypox virus (family Poxviridae, genus Orthopoxvirus); Congo Basin clade causes more severe illness than West African clade

Nonhuman primates, some wild and pet rodents, including Gambian rats, dormice, prairie dogs, African squirrels, dogs, some other mammals (eg, opossums); full host range uncertain

West and central Africa

Contact with lesions, blood or body fluids, fomites; bites; aerosols during close contact

Smallpox-like disease; flu-like symptoms followed by maculopapular rash, which develops into vesicles, pustules, scabs; lymphadenopathy prominent; respiratory signs, encephalitis possible; case fatality rate varies with strain, < 1% to 10%–17% or higher; milder in those vaccinated for smallpox

Murray Valley encephalitis

Murray Valley encephalitis virus (family Flaviviridae, genus Flavivirus)

Wild water birds are reservoirs; rabbits, kangaroos may also amplify virus; some other mammals (eg, horses), dead-end hosts

Australia, New Guinea

Mosquito bites, especially Culex annulirostris

Asymptomatic or mild nonspecific febrile illness in majority; encephalitis, often with neurologic sequelae, or poliomyelitis-like flaccid paralysis in small number of patients; case fatality rate 15%–30% in encephalitic form

Newcastle disease

Newcastle disease virus (Avian paramyxovirus 1 [family Paramyxoviridae, genus Avulavirus])

Domestic and wild birds

Mildly virulent (lentogenic, mesogenic strains) are found worldwide; highly virulent (velogenic) strains found in Asia, the Middle East, Africa, Central and South America, parts of Mexico; also in cormorants in US

Occupational exposure, usually after contact with large amounts of virus

Highly virulent (velogenic) strains can cause self-limiting conjunctivitis, possibly other syndromes (eg, mild influenza-like disease); fatal pneumonia in a severely immunocompromised person

New World hemorrhagic fever (Argentinean, Bolivian, Venezuelan and Brazilian hemorrhagic fevers)

Arenaviruses in Tacaribe complex (family Arenaviridae, genus M Ammarenavirus): Juin virus (Argentine hemorrhagic fever), Machupo virus (Bolivian hemorrhagic fever), Guanarito virus (Venezuelan hemorrhagic fever), Sabiá virus (Brazilian hemorrhagic fever), Chapare virus; possibly others

Rodents

South America

Viruses found in rodent excretions, secretions, tissues; inhalation of aerosolized virus or direct contact with mucous membranes or broken skin

Gradual onset of nonspecific clinical signs, including myalgia, headache, and fever; may develop petechial or ecchymotic hemorrhages, bleeding, CNS signs, hypotension/shock; case fatality rates differ between viruses

Nipah virus infection

Nipah virus (family Paramyxoviridae, genus Henipavirus)

Fruit bats of the genus Pteropus are normal reservoir; swine can be reservoir; occasionally in other mammals (spillover hosts)

Malaysia, Bangladesh, Northern India; apparent outbreak (or closely related virus) in Philippines; virus is probably endemic in southeast Asia; however, outbreaks seem to cluster in certain geographic areas

Direct contact with infected pigs or contaminated tissue; direct or indirect (eg, contaminated fruit juice) bat-to-human transmission; outbreak in Philippines linked to contact with horses; person to person transmission occurs

Initial signs flu-like with fever, headache, myalgia, sometimes vomiting; encephalitis and meningitis; respiratory disease, including acute respiratory distress syndromes in some; septicemia; other complications in severely ill; case fatality rate 38%–75%

Omsk hemorrhagic fever

Omsk hemorrhagic fever virus (family Flaviviridae, genus Flavivirus); member of tickborne encephalitis virus serocomplex

Voles, muskrats; also found in other animals

Siberia

Tick bites (Dermacentor spp); direct contact with body fluids or carcasses of muskrats and possibly other animal hosts

Biphasic febrile illness with headache, GI signs, ± hemorrhages (nose, gums, lungs, uterus); CNS signs in minority of patients; mortality rate < 3%

Powassan virus encephalitis

Powassan virus (family Flaviviridae, genus Flavivirus); member of tickborne encephalitis serocomplex

Rodents and other small mammals thought to be reservoirs; evidence for infection in many other mammals, some birds

North America, eastern Russia

Tick bites, especially Ixodes spp, possibly other routes of transmission

Nonspecific febrile illness; may progress to neurologic signs, which can sometimes be severe; some cases fatal

Rabies and rabies-related infections

Lyssaviruses:rabies virus (family Rhabdoviridae, genus Lyssavirus) and related lyssaviruses, Duvenhage virus, Mokola virus, Australian bat lyssavirus, European bat lyssaviruses 1 and 2, Irkut virus, possibly others  

Wild and domestic canids, Mustelidae, Viverridae, Procyonidae, and order Chiroptera (bats) are important reservoir hosts for rabies; bats are reservoir hosts for the rabies-related viruses except Mokola virus, which might be carried in rodents and shrews; probably all mammals are susceptible

Rabies is worldwide with a few exceptions: rabies-related lyssaviruses are found only in eastern hemisphere (distribution varies)

Exposure to saliva of diseased animals through broken skin or mucous membranes, often in bites; aerosols in closed environments

Paresthesias or pain at bite site; nonspecific prodromal signs such as fever, myalgia, malaise; mood changes progress to paresthesias, paresis, seizures, and many other neurologic signs; survival in clinical cases thought to be very rare

Rift Valley fever

Rift Valley fever virus (family Bunyaviridae, genus Phlebovirus)

Sheep, goats, cattle, water buffalo, African buffalo, camels, nonhuman primates; squirrels and other rodents; puppies and kittens

Africa

Mosquito bites; contact with animal tissues, aerosolized virus in laboratories or animal slaughter

Influenza-like febrile illness in most; complications can include renal disease, meningoencephalitis, ocular disease or hemorrhagic syndrome with liver involvement; death uncommon except with hemorrhagic syndrome

Ross River virus infection, Ross River fever; epidemic polyarthritis

Ross River virus (family Togaviridae, genus Alphavirus)

Marsupials, important amplifying hosts; possibly also amplified by horses, other mammals during epizootics

Australia, South Pacific Islands

Mosquito bites (especially Culex annulirostris and Aedes spp)

Mild fever, arthralgia ± arthritis, headache, rash; small joints most affected but large joints can also be involved; arthralgia, myalgia, lethargy may persist for months

St. Louis encephalitis

St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus)

Wild birds are major hosts; mammals (eg, rodents, bats) might also be involved in some locations

Western hemisphere

Mosquito bites, especially Culex spp

Flu-like illness sometimes followed by meningitis or encephalitis, focal neurologic signs; more severe in elderly and those with debilitating diseases; case fatality rate of 5%–20% reported in epidemics

Severe acute respiratory syndrome (SARS)

SARS coronavirus (family Coronaviridae, genus Coronavirus)

Bats are thought to be reservoir hosts; can also infect palm civets, raccoon dogs, cats, pigs, ferrets, rodents, nonhuman primates, other mammals; palm civets might have role in transmission to humans but uncertain

China, southeast Asia

Contamination of mucous membranes with respiratory droplets or virus on fomites; possibly aerosol transmission

Mild upper respiratory or flu-like illness (sometimes with diarrhea) to severe pneumonia; generally more severe in people with comorbidities, elderly or immunocompromised, but also severe in some healthy people; multiorgan failure possible; fatality rate among known cases ranged from 6%– 17% in different areas

Severe fever with thrombocytopenia syndrome (SFTS)

SFTS virus (family Bunyaviridae, genus Phlebovirus); agent appears related to heartland disease virus

Reservoir host unknown; antibodies or viral RNA found in various domestic and wild mammals

Asia

Tick bites (Haemaphysalis longicornis and members of other genera)

Febrile illness with GI signs; thrombocytopenia; multiple organ failure possible; some cases fatal

Sindbis virus disease

Sindbis virus (family Togaviridae, genus Alphavirus)

Birds (passeriformes are main reservoirs or amplifying hosts); occasionally found in other vertebrates

Virus widespread in Eastern hemisphere; outbreaks tend to occur in limited locations but sporadic cases can occur anywhere

Mosquito bites; Culex and Culiseta, also others (eg, Aedes that act as bridge vectors)

Fever, arthritis, rash, prominent myalgia; nausea, vomiting, mild jaundice in some; joint pain can persist for months; seems to be mild or asymptomatic in most children; fatalities appear absent or very rare

Tanapox

Tanapox virus (family Poxviridae, genus Yatapoxvirus); Yaba-like disease virus may be a variant of tanapox virus

Nonhuman primates

Africa, and in monkey colonies

Direct contact through broken skin; mosquitoes suspected to be vector in Africa

Nonspecific febrile illness followed by self- limited papulovesicular or nodular lesions (may be pruritic or tender), often on extremities; number of lesions varies but often 1–2

Tickborne encephalitis (far eastern tickborne encephalitis, Russian spring-summer encephalitis, central European tickborne encephalitis)

Tickborne encephalitis virus (TBEV) (family Flaviviridae, genus Flavivirus); three major subtypes: European (TBEV-Eu [least virulent]), Siberian (TBEV-Sib), Far Eastern (TBEV-FE)

Small mammals especially rodents; important in maintaining virus; ruminants, dogs, horses, and other mammals; birds can be infected

Eurasia; TBEV-Eu mainly Europe to former USSR; TBEV-FE mainly Asia to former USSR; TBEV-Sib mainly in Siberia

Tick bites (mainly Ixodes ricinus and I persculatus; also other species); may be ingested in unpasteurized milk and milk products

Often biphasic, with flu-like febrile illness in initial stage; neurologic signs from mild meningitis to severe encephalitis in some; myelitis or flaccid poliomyelitis-like paralysis (usually arms, shoulders, levator muscles of head); possibility of chronic and progressive forms; cases with hemorrhagic signs reported in parts of Russia; case fatality rate in Europe (mainly TBEV-Eu) < 1% but some subtypes seem to have higher mortality

Usutu virus infections

Usutu virus (family Flaviviridae, genus Flavivirus)

Birds are reservoir hosts; infections also occur in various mammals including horses, dogs, suids, rodents

Africa, Europe, Middle East

Mosquito bites, mainly Culex spp

Febrile flu-like illness, sometimes with rash; jaundice possible; encephalitis or meningoencephalitis in some; neurologic complications might occur mainly in people with comorbidities or immunosuppression; many cases might be mild/asymptomatic

Vaccinia-related poxviruses

Vaccinia or vaccinia-like viruses (family Poxviridae, genus Orthopoxvirus) of uncertain origin

Reservoir uncertain; found in wild rodents, cattle, horses, nonhuman primates

Appear to be endemic in Brazil

Direct contact

Pox skin lesions (papules, pustules, ulcerative nodules), may be accompanied by fever, lymphadenopathy

Venezuelan equine encephalomyelitis

Venezuelan equine encephalitis virus (VEEV) complex (family Togaviridae, genus Alphavirus)

Enzootic VEEV maintained in rodents, other small mammals, bats, not amplified in equids; epizootic viruses amplified in equids; occasionally in other mammals and birds

Western Hemisphere; enzootic strains probably Florida to South America; epizootic strains emerge in South America, spread, including to North America

Mosquito bites (epizootic VEEV mainly Culex; enzootic VEEV by multiple genera); epizootic viruses possibly also by mechanical vectors including blackflies; exposure to aerosolized debris from infected laboratory rodents; laboratory accidents

Most have nonspecific febrile illness, can be followed by neurologic signs in a small percentage of cases, especially children and to a lesser extent the elderly; encephalitis has case fatality rate of 10%–35% with highest rates in children < 5 yr old; fetal losses in some pregnant women

Vesicular stomatitis

Vesicular stomatitis Indiana virus, vesicular stomatitis New Jersey virus, vesicular stomatitis Alagoas virus, and Cocal virus (family Rhadboviridae, genus Vesiculovirus)

Equids, swine, cattle; occasionally in South American camelids, sheep, and goats; also rodents; serologic evidence of infection in many wild mammals

North and South America; most likely not endemic north of Mexico but sporadic outbreaks

Contact with animals (lesions, secretions) or in laboratory, probably also from insect bites, including mosquitoes and biting flies (Lutzomyia spp, Culicoides midges, and blackflies)

Usually asymptomatic; may develop acute, self-limited, febrile flu-like illness; vesicles sometimes found in mouth, pharynx, or inoculation site (eg, hands); one case of encephalitis in young child attributed to VSV

Wesselsbron fever

Wesselsbron virus (family Flaviviridae, genus Flavivirus)

Ruminants, especially sheep, goats; also evidence of infection in other mammals, including rodents; lemurs; can infect birds

Africa

Mosquito bites (mainly Aedes spp, possibly others); also by contact with contaminated material especially in the laboratory

Nonspecific febrile illness ± maculopapular rash or ocular signs in some; few cases described but seems to be self-limiting; one case of encephalitis after accidental laboratory exposure of eye

West Nile fever and neuroinvasive disease

West Nile virus (family Flaviviridae, genus Flavivirus); lineage 1 and lineage 2 viruses are both pathogenic

Birds are primary reservoir hosts; also affects horses, other mammals, alligators, possibly other reptiles and amphibians

Eastern and western hemisphere

Mosquito bites (primarily , Culex spp); also by handling infected birds or reptiles or their tissues

Nonspecific febrile illness, occasionally with rash; some cases progress to encephalitis, meningitis, and/or acute flaccid paralysis that resembles poliomyelitis; occasionally other syndromes; < 1% develop neurologic disease but case fatality rate ~10% in all patients with this form and higher in the elderly

Western equine encephalomyelitis

Western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus)

Birds are reservoir hosts, may also cycle in jackrabbits; equids and other mammals are dead-end (incidental) hosts and do not amplify; reptiles might help overwinter

Americas

Mosquito bites; Culex tarsalis important in maintenance cycle in birds in North America; also transmitted by other genera especially Aedes

Nonspecific febrile illness may be followed by encephalitis in infants and children, uncommonly in healthy adults; case fatality rate 3%–4%

Yellow fever

Yellow fever virus (family Flaviviridae, genus Flavivirus); only sylvatic cycle is zoonotic (humans are reservoir for urban cycle)

Nonhuman primates

South America, Africa

Mosquito bites (Haemagogus spp and Sabethes spp in sylvatic cycles in South America, Aedes spp in sylvatic cycles in Africa)

Nonspecific, mild to severe febrile illness followed by liver and renal failure in some; hemorrhages (eg, epistaxis, hematemesis, melena, uterine hemorrhage) and often jaundice in severe cases; can be fatal

Zika virus infection

Zika virus (family Flaviviridae)

Nonhuman and human primates are likely the main reservoirs of the virus

Africa, the Americas, Southern Asia, Western Pacific

Mosquito bites (infected Aedes mosquitoes [A aegypti and A albopictus])

Many people are asymptomatic; acute onset of fever with maculopapular rash, arthralgia, conjunctivitis, myalgia, headache; there have been cases of Guillain-Barré syndrome reported in patients following suspected Zika virus infection; infection during pregnancy is a cause of microcephaly and other severe fetal brain defects

Prion Disease

Variant Creutzfeldt-Jakob disease

Bovine spongiform encephalopathy prion

Cattle are most important host; also infects other ruminants, cats and other felids, lemurs

Most cases in the UK but also in many other countries

Ingestion of bovine products, especially those contaminated with CNS tissues

Neurodegenerative disorder similar to sporadic Creutzfeldt-Jakob disease but often in younger patients and progresses more rapidly; always fatal