A survey of human cases of H5N1 avian influenza reported by the WHO before June 2006 for infection control

H5N1 avian influenza has been widely spreading in fowls in the Eastern Hemisphere and caused hundreds of severe human cases. Here, the information of the 224 human cases of H5N1 avian influenza reported by the World Health Organization before June 2006 were surveyed and analyzed. The results suggested that human infections escalated in the past 3 years, and control of animal H5N1 influenza, avoidance of high-risk behaviors, and proper disposal of diseased or dead fowls are vital for the prevention of the human infections. Age distribution of the human cases demonstrated that older people are more immune to the infection, possibly because of the cross protectivity induced by their previous infections with human influenza A viruses. This survey also suggested that live vaccines against human influenza may be of utility in the prevention of the avian influenza virus infections in humans, and new preventive measures should be considered for the control of animal H5N1 influenza epidemics, which are likely more serious than indicated by official reports.