7. Transmission of hantaviruses
Although hantaviruses can be inactivated by heating at 60% for 30
minutes, organic solvents, hypochlorite solvents, or ultraviolet
light,5 they are relatively stable in the external
environment. They can survive for 10 days at room temperature and more
than 18 days at low temperatures (e.g., 4°C).12 This
facilitates the transmission of hantaviruses.
Different from the fact that various bunyaviruses (e.g., Rift Valley
fever virus) are transmitted by insects, human hantaviruses are mainly
transmitted by rodents.45,54,68 Hantaviruses usually
cause asymptomatic and persistent infections in rodents, except that
Syrian hamsters infected with ANDV can show typical symptoms of
HCPS/HPS. Rodents, shrews, moles, and bats are the reservoirs of some
hantaviruses, which can transmit the virus horizontally and vertically.
Infected animals can spread hantaviruses to other sensitive animals
through aerosols or droplets formed from their excreta or secretions
(feces, urine, saliva), through the consumption of contaminated food, or
through biting and scratching.69,70 They can also
transmit the hantavirus through the fecal-oral route, and females can
transmit the virus through the placenta or sucking.71Mating and fighting among sensitive animals also aids in virus
transmission.72
Rodents can also transmit hantaviruses to humans through aerosols or
droplets formed from their excreta and through the consumption of
contaminated food.3 Rodent bites and scratches are
important for virus transmission to humans.73 The
prevalence rate of hantaviruses (e.g., SEOV) is up to 80% among traders
who cultivate and breed rodents and those who keep pet rodents (e.g.,
rats and mice).74,75 An outbreak of SEOV in North
America with 31 confirmed cases of infection resulted from contact with
pet rats.73
ANDV is currently the only known hantavirus that can be transmitted from
humans to humans. It usually occurs after close contact with an infected
person.76 ANDV may be secreted into human saliva and
transmitted through the respiratory tract via airborne droplets released
by coughing or sneezing.77 Studies have shown that
ANDV can also be transmitted to newborns through breast milk, and
transmission between humans can also occur through the digestive tract
or placenta.78
Investigations have shown that HFRS can be transmitted to animals or
humans through the bites of mites.79,80 Investigations
have also shown that pigs can be infected with HTNV without severe
symptoms,81 and sows can vertically transmit the virus
through the placenta.82 A swine breeder was infected
with hantavirus, but with no history of mite bites or rodent infestation
in the living environment, so the pig-to-human transmission of the virus
could be possible.83 However, the relevant
investigations have been neglected, possibly because they were published
in Chinese.
HTNV and PUUV antibodies have been detected in cattle, deer, and
rabbits. SNV antibodies have been detected in cats and
dogs.84 The roles of these mammalian hosts in the
ecology of hantaviruses remain unknown.