Taiwan Epidemiology Bulletin

Taiwan Epidemiology Bulletin

vol.40 No.13

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Original Article

Laboratory Genotyping Analysis of Suspected Acute Hepatitis A Outbreaks, Taiwan, 2022

DOI: 10.6524/EB.202407_40(13).0001

Wei-Lun Huang*, Pei-Yu Su, Yi Chu, Chiu-Chu Hsu, Jyh-Yuan Yang

2024 Vol.40 No.13

Correspondence Author: Wei-Lun Huang*

  • Center for Research, Diagnostics and Vaccine Development, Centers for Disease Control, Ministry of Health and Welfare, Taiwan


        The Center for Diagnostics and Vaccine Development of Taiwan Centers for Disease Control was notified by the Southern, Central, and Northern Regional Centers of suspected acute hepatitis A outbreaks starting in January 2022. By the end of July 2022, 10 outbreaks were reported, involving 85 confirmed cases and contacts. Among the 26 cases that tested positive for hepatitis A virus using real-time PCR, all were Thai, and their genotypes were IA cluster 2. The sequence similarity was 100%, confirming an outbreak. No records of any of the Thai workers leaving Taiwan after their arrival were identified, and the positive cases had been working in Taiwan for longer than the incubation period of hepatitis A. The outbreak had cases scattered across northern, central, and southern Taiwan. Investigations found no apparent linkage among the cases, as they did not know each other. It was speculated that this year's outbreak was a foodborne infection of hepatitis A virus.

Keywords:acute hepatitis A, outbreak, genotype, phylogenetic analysis

Outbreak Investigation

Investigation of A Suspected Hepatitis A Outbreak Associated with Genotype IIIA, Taiwan, January-March 2023

DOI: 10.6524/EB.202407_40(13).0002

Yen-I Lee*1, Chia-Ping Su1, Wei-Lun Huang2, Jyh-Yuan Yang2

2024 Vol.40 No.13

Correspondence Author: Yen-I Lee*1

  • 1Office of Preventive Medicine, Centers for Disease Control, Ministry of Health and Welfare, Taiwan
  • 2Epidemic Intelligence Center, Centers for Disease Control, Ministry of Health and Welfare, Taiwan


        In March 2023, Taiwan Centers for Disease Control identified genetic analysis results of six newly identified patients of acute hepatitis A, of which five were indigenous, and all belonged to genotype IIIA with high genetic similarity. Previously, the prevalent genotype in locally acquired hepatitis A cases was IA, suggesting a potential outbreak of genotype IIIA acute hepatitis A. The preliminary investigation excluded the potential risk of intravenous drug use or needle sharing. We conducted a case-control study; a case was defined as an individual with indigenous acute hepatitis A infection of genotype IIIA, demonstrating high genetic similarity as confirmed through genotyping in March 2023. We interviewed five cases, assessing their demographics, symptoms, and dietary history a month before onset or diagnosis. Statistical analysis using Fisher's exact test compared findings to the general population. Consuming raw fish and shrimp in the month before illness was identified as a potential risk factor, but the specific source of infection remains unidentified. Continuous surveillance of genotype IIIA acute hepatitis A cases is recommended. Public awareness of food hygiene, particularly avoiding the consumption of raw seafood, is essential. Individuals without hepatitis A antibodies or at high risk should consider vaccination to reduce the infection risk.

Keywords:Hepatitis A, genotype IIIA


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