Recent outbreaks of avian influenza in Japan

Recently Japan had three outbreaks of avian influenza (Al) in 2004, 2005 and 2007. An outbreak of highly pathogenic avian influenza (HPAI) was recorded in early 2004, the first for 79 years, with four farms being infected with HPAI virus subtype H5N1. In 2005, 41 farms were found to be infected with AI virus subtype H5N2. In early 2007, four farms were infected with HPAI virus subtype H5N1 again. In all of these outbreaks, the disease was eradicated without resorting to vaccination, through a campaign of culling, movement control of chickens in areas around infected premises, and intensive clinical and serological surveillance. This paper describes the nature of the outbreaks, the eradication measures implemented, clinical and serological surveillance techniques used, and the possible sources of infection.