Exploring hepatitis A dynamics in Israel, 2019-2022

Background: Continuous monitoring of Hepatitis A Virus (HAV) may assist in identifying local outbreaks. The advent of the COVID-19 pandemic, which affected the circulation of numerous pathogens, may have also impacted the scope of HAV infections.

Aim: To investigate the incidence and environmental dissemination of HAV between 2019 and 2022 in Israel, a country with an anti-HAV vaccination program.

Methods: HAV RT-PCR analysis was performed for all HAV cases and for 280 sewage samples collected in 2019-2022. Available amplified HAV fragments from clinical (n = 107) and sewage (n = 27) were also assessed by genotyping and phylogenetic analysis.

Results: In 2019-2022, 158 individuals and 12.9 % (36/280) of sewage samples were HAV-RNA positive. Median age was 30 years (IQR 20.5-44); approximately half (51.9 %, 82/158) were males. Almost all patients (98.4 %, 124/126) were not vaccinated. Highest numbers were identified in 2019 (84 cases and 30 %, 21/71, positive sewage samples). In 2020, when three COVID-19 related lockdowns were implemented, 24 cases and 4.3 % (3/69) sewage samples were HAV-RNA positive. The number of HAV-RNA positive cases and positive sewage samples remained low in 2021-2022 (31 and 19 cases, 13.2 %, 9/68 and 4.2 %, 3/72 positive sewage samples, respectively). Sub-genotype IB dominated (90.7 %, 97/107 of cases and 81.5 %, 22/27 of sewage samples), and phylogenetic analysis of HAV samples demonstrated small transmission clusters of sequences from Jews, Bedouin Arabs and foreign workers. Sub-genotype IA was identified in 8.4 % (9/107) of cases and in 18.5 % (5/27) of sewage samples.

Conclusion: Combined clinical and environmental surveillance is optimal for monitoring HAV. In 2020, the circulation of HAV decreased, possibly following COVD-19 health restrictions. In subsequent years, the incidence remained low. Adults in risk-groups for HAV infection should be vaccinated to minimize HAV circulation.