Seasonal Influenza Activity in Japan, and Epidemiological Investigation for Avian Influenza.

Abstract

We analyzed the seasonal influenza activity in 2004/05 and 2005/06 seasons. In 2004/05 season, the prevalence of influenza started lately. The arrival of a peak of influenzal prevalence was the ninth week, and was late in comparison with an average year. The prevalence scale was very large, and the estimation number of patients was 17700000. Since the start of the 2004/05 season, influenza activity has mainly been associated with influenza B viruses. The start of prevalence of 2005/06 season was 50th week and was comparatively early. The peak of the prevalence was the 4th week, same as an average year. Since the start of the 2005/06 season, influenza activity has mainly been associated with influenza A/H3 viruses.
H5N1 highly pathogenic avian influenza virus have spread through Africa and Europe from Asia. For purpose such as inhibition of the outbreak of new variant influenza, the prevention of human to human infection and expansion, early containment, the public health organization has to do unified epidemiological investigation immediately nationwide. By doing epidemiological investigation, the prevention of infection expansion, specification of the source of infection, assessment of the risk of infection, and early detection of new variant influenza virus and containment, are expected.