Seven integrated influenza surveillance systems in Taiwan

Abstract

Background: Influenza surveillance in recent decades in Taiwan showed that the major virus isolates were A/Hong Kong/68-like (H3N2), A/England/42/72-like (H3N2), A/Taiwan/1/86 (H1N1), A/Texas/36/91-like (H1N1), A/Taiwan/112/96 (H1N1), and A/Taiwan/118/96 (H1N1) based on passive virologic surveillance before 1999. Materials and methods: To prevent the potential public health threat of a newly emerged influenza A strain like H5N1 in Hong Kong, seven surveillance systems have been established in Taiwan since 1999, including severe case reporting, sentinel physician, contract-laboratory, poultry market, domestic avian, wild bird and pig surveillance. Scientific exchanges and possible public health actions are discussed in regular meetings during the winter season. Results: The isolation rates of influenza A virus were higher among ducks than chickens in both domestic avian and market surveillance systems. Ten subtypes of influenza A virus can be found in migrating wild birds, which may serve as a reservoir for the genetic and antigenic changes of the virus. The H6 subtype was isolated from both wild birds and market surveillance systems. Pig surveillance found that H3 occurred more in the winter, whereas H1 appeared predominantly in the summer. Human virologic surveillance also demonstrated summer and winter peaks. Market surveillance in Taipei showed H6, H4, and H3 subtypes isolated from ducks only. Sentinel physician surveillance experience has taught us the importance of involving local clinics, particularly in farm areas. The traditional passive physician reporting surveillance provided limited information and it was replaced by severe case reporting. Most elderly physicians in Taiwan did not like to report influenza even after implementation of direct electronic reporting through a worldwide web system. More modern technology will be applied to increase the timeliness and representativeness of influenza surveillance in preparing for future pandemics. Conclusion: Integration of animal and human influenza surveillance systems in the high population density in Taiwan serves as a model in the efforts of global influenza surveillance to detect newly emerged influenza virus strains via several channels, particularly useful in detecting severity of cases and inter-species transmission.