H5N1 avian influenza virus replicates very aggressively in humans, and these high viral levels set off an overwhelming inflammatory response, factors that help explain the infection's virulence, according to new research (de Jong M et al. Nat Med. doi:10.1038/nm1477 [published online ahead of print September 10, 2006]).
Researchers at the Oxford University Clinical Research Unit at the Hospital for Tropical Disease in Ho Chi Minh City, Vietnam, studied 18 patients infected with H5N1 influenza and 8 patients with 2 types of human influenza. Those infected with H5N1 virus had much higher levels of virus in the throat compared with those infected with the other viruses. In addition, levels of some inflammatory cytokines and chemokines were correlated with viral load and were highest in the patients who died. One cytokine, interleukin 8, is produced by bronchial epithelial cells and may play a role in acute respiratory distress syndrome.
Stephenson J. Avian Flu’s Lethality. JAMA. 2006;296(15):1830. doi:10.1001/jama.296.15.1830-c