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

1 Vantaa Research Unit, Finnish Forest Research Institute, PO Box 18, FIN-01301 Vantaa, Finland 2 Department of Biological and Environmental Science, PO Box 35, FIN-40014 University of Jyväskylä, Finland 3 Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden 4 Microbiology and Tumor Biology Center, Karolinska Institutet, SE-171 77 Stockholm, Sweden 5 Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, University of Helsinki, PO Box 66, FIN-00014 University of Helsinki, Finland 6 Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland 7 HUCH Laboratory Diagnostics, PO Box 403, FIN-00029 HUS, Helsinki, Finland Correspondence Åke Lundkvist Ake.Lundkvist{at}smi.ki.se 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 °C, but were inactivated after 24 h at 37 °C. Interestingly, a fraction of dried virus was still infectious after 1 h at 56 °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. Published online ahead of print on 28 April 2006 as DOI 10.1099/vir.0.81643-0.