Characterization of influenza A/HongKong/156/97 (H5N1) virus in a mouse model and protective effect of zanamivir on H5N1 infection in mice

A recent outbreak of influenza in Hong Kong was caused by a highly virulent virus of avian origin. Concern that the appearance of such a virus in the human population may be a harbinger of a new pandemic has brought increased attention to the issue of antivirals available for treatment of influenza. A/HongKong/156/97 (H5N1), the first virus of H5N1 subtype isolated from a human host, is highly virulent in the mouse model and can infect mouse lung s without requiring adaptation. High mortality and evidence of systemic dis ease, including spread to the brain after intranasal inoculation, are obser ved. Zanamivir, a novel neuraminidase inhibitor, is effective at decreasing replication of the virus in vitro. In a model of lethal challenge in mice, zanamivir reduces lung titers of the virus and decreases morbidity and mor tality.