HEPATITIS A OUTBREAK IN MEN HAVING SEX WITH MEN IN ISRAEL 2017: ENVIRONMENTAL AND CLINICAL SURVEILLANCE

Background: Hepatitis A virus (HAV) affecting men having sex with men (MSM) has recently been reported in European and US cities as well as in Israel. We report the clinical and environmental surveillance of this outbreak in Israel during 2017.

Methods: Anti-HAV(IgM) positive blood samples collected during 2017 (N=81) and 147 sewage samples collected monthly from 14 facilities around the country were included;56/81 blood and all sewage samples were analyzed by Real-time PCR (RT-PCR). Sequencing of the VP1-2a region was performed. Phylogenetic analysis included the current HAV-1a European outbreak strains.

Results: Patients median age: 34y (range 3-56y); M/F 69/24 (85.2% M); 32/69 self-identified as MSM, of whom 24 (75%) were from the Tel-Aviv area as compared to 13/37(35%) of the non-MSM males. HAV vaccination records were available for 43/81; 40/43 were unvaccinated. Almost all HAV-positive MSM cases (96%, 27/28) were infected with one of the two European derived 1a subtypes HAV sequences with similar clustering were also identified in 31% (45/147) of sewage samples, with a high prevalence (63%, 26/41) in facilities in the Tel-Aviv area. The rate of HAV-positive clinical and sewage samples declined towards the end of 2017 (Figure 1).

Conclusion: These results describe an ongoing HAV 1a outbreak in MSM in Israel, imported, at least in part, from European countries. Despite the efficient universal mass vaccination program which lead to an annual HAV incidence of 2,5 cases/100,000, HAV can still be transmitted to the unvaccinated, high-risk adult population and raise the issue of catch-up vaccination. The importance of environmental sampling in disease surveillance is also demonstrated. The decline in positive clinical and sewage samples in end of 2017 suggests the outbreak has been halted.