Excess mortality and influenza surveillance in Taiwan.

Excess mortality has proven to be a useful epidemiologic tool for influenza surveillance in the temperate zone. A retrospective analysis of the epidemiology of influenza in Taiwan was undertaken to explore the usefulness of this technique in the tropical--subtropical zone. Excess mortality similar to that observed during influenza epidemics in the temperate zone was noted during periods of previously recognized influenza epidemics in Taiwan. For the very young and the elderly excess mortality was observed to be even higher than in the temperate zone. Virus isolations, increased school absenteeism, and high clinical attack rates were also noted during influenza epidemics. Use of these epidemiologic techniques in Taiwan proved to be a useful approach to describe the impact of influenza.