Outbreaks of High Pathogenic Avian Influenza in Ibaraki Prefecture-From the Interim Report of HPAI Transmission Route Investigation Team-

Outbreaks of High Pathogenic Avian Influenza (HPAI) were found in Ibaraki Prefecture in June of 2005. Antibodies against HPAI or HPAI virus were confirmed at 31 layer farms until September of 2005. The agent was identified as HPAI H5N2 subtype by serological or genetic tests. The virulent of virus was very weak for chicken and chickens showed no symptoms. The virus was very close to the isolates of Middle America in 2000-2002 by genetic study. The invasion routes of the virus to Japan were considered as follows: 1) carried by migratory birds, 2) transmitted by imported bird or chicken meat from Middle America, 3) carried in by man intentionally or not intentionally. However there are no birds to migrate between Middle America and Japan, and also it is not permitted to import birds and bird's meat from Middle America. Transmission route of this virus has not yet been clear. It is necessary to investigate more on farms and epidemiological relationship adding the data of new 10 outbreak farms.