Circulation of Hepatitis A in Israel 2017-2018: Environmental Surveillance Supports Clinical Findings

Background and Aims: Hepatitis A virus (HAV) is a major cause of acute viral hepatitis worldwide. In Israel, since the introduction of universal toddler vaccination program in 1999, the number of HAV infections has dramatically decreased. However, outbreaks affecting vulnerable populations do occur. The last outbreak of HAV in non-vaccinated MSM, which started in the end of 2016, triggered the introduction of a systematic molecular investigation of circulating HAV genotypes in all clinical cases and in environmental samples (ES). This study summarizes the impact of this ongoing surveillance on the monitoring of such an enteric disease.

Method: ES collected monthly during 2017 (n=113) and 2018 (n= 109) from 11 main sewage treatment facilities and 58/86 in 2017 and 66/87 in 2018 HAV IgM positive samples from individuals reported to the ministry of health, were available for this study. Real-time PCR and sequencing of the VP1-2A region were performed according to national protocols.

Results: 40% (45/113) and 26% (28/109) of all ES collected in 2017 and 2018, respectively, were HAV positive and most (63/73) could be successfully subtyped. While 76% (32/42) and 14% (6/42) in 2017 were HAV-1A and HAV-1B positive, respectively, in 2018 5% (1/21) and 95% (20/21) were HAV-1A and HAV-1B positive, respectively. Overall, 79% (98/124) of the available HS samples were PCR positive. Similar to the ES results, 79% (41/52) and 19% (10/52) in 2017 were HAV-1A and HAV-1B positives while the majority of patients in 2018, 83%, 38/46, had HAV-1B and only 13% (6/46) had HAV-1A (Figure 1). The location of positive HAV-1A and 1B ES highly correlated with patients’ residence. Other HAV genotypes (HAV-3a/b) were rare (<3%, 5/147), and identified only in patients only.

Conclusion: Continuous surveillance of HAV in sewage and confirmation of positive serology results with HAV RNA analysis may assist in correct diagnosis, disease monitoring and identification circulating genotypes in local HAV outbreaks.