The antiviral drug peramivir might offer humans significant protection during a pandemic of the avian influenza virus H5N1, according to results of mouse studies conducted by investigators at St. Jude Children's Research Hospital. Peramivir, an antiviral drug, blocks the ability of influenza viruses to use an enzyme called neuraminidase, thus preventing the release of new virus particles and their spread from one infected cell to another. The researchers reported 100 percent survival among 10 infected mice given intramuscular injections of peramivir daily for eight days. The drug also inhibited the replication of the deadly strain of H5N1 virus in the lung, brain and spleen. The key to the high survival rate was treating the infected mice within 24 hours after infection with H5N1 and continuing the treatment for eight days. "Peramivir should be given as soon as H5N1 infection is suspected, since onset of symptoms in infected humans can be delayed," said David A. Boltz, Ph.D., a postdoctoral fellow in the laboratory of Robert G. Webster in the Infectious Diseases department at St. Jude. "The drug could also be given as a preventive measure during an outbreak to decrease the risk of infection." Boltz is first author of a paper that was presented Mon., April 30 at the 20th International Conference on Antiviral Research in Palm Springs, Calif. "We were surprised that we could also see a 40 percent survival rate among mice after just a single dose of peramivir," said Elena A. Govorkova, Ph.D., a scientific manager in the Infectious Diseases department at St. Jude. Govorkova is the paper's senior author. "We are currently studying the emergence of H5N1 variants that are resistant to this drug and may occur in the course of treatment," said Natalia A. Ilyushina, Ph.D., a postdoctoral fellow in Webster's laboratory and a co- author of the paper. Other authors of this report include Robert G. Webster (St. Jude) and C. Shane Arnold and Y. Sudhakar Babu (BioCryst Pharmaceuticals Inc., Birmingham, Ala.). This study was supported by National Institute of Allergy and Infectious Diseases, the U.S. Public Health Service, BioCryst Pharmaceuticals and ALSAC. St. Jude Children's Research Hospital St. Jude Children's Research Hospital is internationally recognized for its pioneering work in finding cures and saving children with cancer and other catastrophic diseases. Founded by late entertainer Danny Thomas and based in Memphis, Tenn., St. Jude freely shares its discoveries with scientific and medical communities around the world. No family ever pays for treatments not covered by insurance, and families without insurance are never asked to pay. St. Jude is financially supported by ALSAC, its fundraising organization. For more information, please visit