[Morbidity and mortality of influenza in Japan]

Influenza is reportable in Japan since 1947. The current sentinel surveillance system for influenza started in 1987. Influenza morbidity is clearly correlated with increased influenza and pneumonia mortality and mortality from other major underlying diseases, which results in an increased overall mortality. The expected mortality was calculated from a seasonal ARIMA model for influenza and pneumonia. Excess mortality is defined as the number of deaths exceeding the upper confidence limit that was calculated from the model. During the 1998/1999 season, the estimated number of excess deaths from pneumonia and influenza was about 10,000 and from all causes about 40,000. More than 90% of these deaths occurred among elderly.