Prolonged survival of Puumala hantavirus outside the host:: evidence for indirect transmission via the environment

The capability of rodent-borne viruses to survive outside the host is critical for the transmission dynamics within rodent populations and to humans. The transmission of Puumala virus (PUUV) in colonized bank voles (Clethrionomys glareolus) was investigated and additional longevity studies in cell culture with PUUV and Tula (TULV) hantaviruses were performed. Wild-type PUUV excreted by experimentally infected donor bank voles was shown to be transmitted indirectly between rodents through contaminated beddings, and maintained its infectivity to recipient voles at room temperature for 12-15 days. In cell culture supernatants, PUUV and TULV remained infectious for 5-11 days at room temperature and up to 18 days at 4 degrees C, but were inactivated after 24 h at 37 degrees C. Interestingly, a fraction of dried virus was still infectious after 1 h at 56 degrees C. These results demonstrated that hantavirus transmission does not require direct contact between rodents, or between rodents and humans, and that the indirect transmission of PUUV through contaminated environment takes place among the rodents for a prolonged period of time. The results also have implications for safety recommendations for work with hantaviruses and for preventive measures.