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.