From January 2004 to March 2004, there were outbreaks of acute, highly transmissible, lethal diseases in chickens at four poultry farms in Japan: one in Oita, one in Yamaguchi, and two in Kyoto Prefecture ( Figure 1 ). Virus isolates from infected chickens were all identified as influenza A virus of the H5N1 subtype [5] . Such highly pathogenic avian influenza (HPAI) epidemics had not been reported in Japan for 79 years. Two avian influenza outbreaks at poultry farms in Tamba Town, Kyoto Prefecture, were the last two outbreaks of the 2004 avian epidemics in Japan. Since then, there were outbreaks of H5N1 avian influenza in Okayama and Miyazaki Prefectures in 2007. The H5N1 virus was also isolated from dead Whooper swans, Cygnus cygnus, in 2008 in Towada Lake, Akita Prefecture [6] . In addition, outbreaks of other subtypes of avian influenza virus have frequently occurred in Japan. The H5N2 avian influenza was reported in Ibaraki and Saitama Prefectures in 2005 and 2006, the H3 subtype was reported in Saitama Prefecture in 2009, and the H7 subtype was in Aichi Prefecture in 2009. We know of no report suggesting that H5N1 virus could be transmitted efficaciously from person to person, but the possibility remains that such transmission could evolve [7] .