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 fowl in the Eastern Hemisphere and has caused hundreds of severe human cases. Here, information regarding the 224 human cases of H5N1 avian influenza reported by the World Health Organization (WHO) before June 2006 were surveyed and analyzed. The results suggested that human infections escalated in the past 3 years and that control of animal H5N1 influenza, avoidance of high-risk behaviors, and proper disposal of diseased or dead fowl are vital for the prevention of 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 infection with human influenza A viruses. This survey also suggested that live vaccines against human influenza may be of utility in the prevention of avian influenza virus infection in humans and that new preventive measures should be considered for the control of animal H5N1 influenza epidemics, which are likely more numerous than indicated by official reports.