Cases of the highly pathogenic avian influenza A virus (H5N1) causing influenza symptoms in humans were observed in the Hong Kong Special Administrative Region, People's Republic of China in 1997 [1] . A total of 478 laboratory-confirmed cases of influenza A (H5N1) infection were subsequently reported to the World Health Organization (WHO) from 15 countries between November 2003 and February 2010 [2] . More than 90% of these cases were reported in five countries, namely, Indonesia, Vietnam, Egypt, China, and Thailand. Patients \20 years of age accounted for 63% of the cluster cases and 49% of the sporadic cases [3] . The case-fatality rate (CFR) in all cases was 62.1.