A community-wide epidemic of hepatitis A virus genotype IA associated with consumption of shellfish in Yantai, eastern China, January to March 2020

ABSTRACT

During the first quarter of 2020, a considerable increase in reports of symptomatic hepatitis A cases was noted in Yantai, a coastal city in eastern China. This study aimed to characterize the epidemic and identify the probable source. Serum samples from cases with onsets from 1 January to 31 March 2020 and suspected bivalve mollusk samples from the local seafood market were screened for hepatitis A virus (HAV) RNA by PCR amplification and sequencing of the VP1/2A region. We also analyzed the characteristics and risk exposures of these cases. In total, 110 confirmed cases were notified during the epidemic. Among the 103 cases investigated, the median age was 41 years (range: 25–70 years), and 74 (71.8%) were male. Eighty-eight cases (85.4%) reported having eaten shellfish and 72 (69.9%) specifically oysters. HAV RNA was detected and sequenced successfully in 80.2% (69/86) of the cases, as well as in one oyster out of 20 shellfish samples. Phylogenetic analysis revealed that all isolates belonged to a single genotype IA but presented the co-circulation of five distinct genomic sub-lineages. The oyster-derived HAV strain shared over 98.2% nucleotide identity with all clinical strains obtained during the epidemic, particularly 100% homology with the strains of seven cases. These data indicated that contaminated oyster consumption was probably a common source of this epidemic, although multiple HAV strains were involved. We recommend strengthening shellfish surveillance, changing dietary habits in seafood consumption, and encouraging vaccination for target adults in coastal areas with a high prevalence of hepatitis A.

KEYWORDS:

• Hepatitis A virus
• epidemic
• risk factors
• phylogenetic analysis
• genotype
• shellfish

Acknowledgments

We are grateful to all the relevant public health workers from CDCs of 12 counties (districts) of Yantai for their assistance with this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Li Zhang and Aiqiang Xu contributed to the study concept and design. Bingyu Yan, Peng Chen, Jingjing Lu, Xin Meng, and Qing Xu contributed to data acquisition. Peng Chen contributed to the sample collection. Bingyu Yan and Yi Feng were responsible for the hepatitis A experiment. Bingyu Yan and Peng Chen contributed to the data analysis and initial drafting of the manuscript. Li Zhang contributed to the critical review and revision of the article. All authors contributed to the interpretation of data and critical revision of the manuscript.

Additional information

Funding

This work was supported by grants from Taishan Scholar Program of Shandong Province [No. ts201511105], Shandong Medical Health Science and Technology Development Program [No. 2018WS308], and Science&Technology Innovation and Development Plan of Yantai City [No. 2022MSGY069].