| Summary: | 碩士 === 國立臺灣大學 === 流行病學研究所 === 88 === To understand the frequency and possibility of interspecies transmission of avian influenza virus to human populations in Taiwan, we established three surveillance systems: (1) a follow-up virological surveillance system at the National Taiwan University Hospital (NTUH) from Jan. 1998 to May 2000, (2) the biggest wholesale poultry market virological surveillance system in Taipei from Oct. l999 to Mar. 2000, and (3) a serologic surveillance system among avian veterinarians and market workers by microneutralization and hemagglutination inhibition tests to detect the antibodies against avian influenza virus H4N6 and H6N5 subtypes.
The virological surveillance data at NTUH showed that the predominant influenza season was winter to spring, though influenza isolates were found in late summer or autumn. Comparing the age distribution of influenza A and B patients under 10 years old, we found that influenza A patients were significantly younger than influenza B patients (p<0.01).
The virological surveillance of avian influenza A viruses in the poultry market obtained 28 isolates in total with isolation rate of 4%, including 12 H3 subtypes, 14 H4 subtypes, and 2 H6 subtypes from 700 duck feces samples. Molecular evolution analysis of HA and NP genes of 14 isolates revealed that they all belong to Eurasian lineage of avian influenza viruses. Three of our isolates: 8-12 (H3), 10-24 (H4), and 10-22 (H4) were in the same lineage of A/Hong Kong/156/97 (H5N1), A/Goose/Guangdong/1/96 (H5N1), and A/Quail/Hong Kong/G1/97 (H9N2) by NP gene analysis. These data showed that avian influenza A virus isolated from poultry market in Taiwan may still have pandemic potential in the future.
Seroepidemiological study among 195 poultry workers and 146 veterinarians distributed all over Taiwan areas found seronegative antibody responses against H4 and H6 subtypes. Questionnaire data analysis showed that weather, altitude, raising animal number or species were not the major influential factor of interspecies transmission. However, farm raising and management style and the ecology niche of many different animals (including wild birds, ducks, chicken and pigs) in that locality were predominant determinants to facilitate the virus cross transmission among various host species.
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