High impact of molecular surveillance on hepatitis A outbreak case detection in Sweden: a retrospective study, 2009 to 2018

Hepatitis A notifications in the EU/EEA, 2010-2019: what can we learn from case reporting to the European Surveillance System?

BackgroundEuropean Union/European Economic Area (EU/EEA) countries annually report hepatitis A (HepA) notifications to The European Surveillance System (TESSy).AimTo describe EU/EEA HepA notifications from 2010 to 2019 and identify infection drivers and surveillance improvements.MethodsWe analysed demographic, clinical and transmission information of HepA confirmed cases from TESSy. We stratified countries by population susceptibility profile and performed time-series analysis to describe trends in notification rates, sex distribution and travel history.ResultsTwenty-nine EU/EEA countries reported 139,793 HepA cases. Six eastern EU countries reported > 60% of these cases. EU/EEA notification rate during the study period was 3.2 cases per 100,000 population (range 2.7-5.6). Notifications peaked in 2014 and 2017, with marked differences in case demographic characteristics. Notification trends varied across different country susceptibility groups. In 2017, the proportion of males (74%) and case median age (31 years) increased steeply, while no changes occurred in 2014. Travel history showed seasonal case peaks following the summer. More than 47,000 hospitalisations were reported. Annual case fatality was < 0.2% for all years. Information on travel history, hospitalisation, death and mode of transmission was suboptimal.DiscussionApart from some countries in its east, the EU/EEA is characterised by low HepA incidence baseline and susceptible to recurrent large cross-border outbreaks. Analysis of European surveillance data highlighted the need for stronger prevention policies for eastern EU countries, men who have sex with men and travellers. Improving surveillance data-quality will enhance knowledge on food-borne, and travel-related exposures to inform more effective and tailored regional prevention policies.

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

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.

Detection and control of an ongoing international outbreak of hepatitis A among the Irish Traveller community beginning September 2020

Hepatitis A virus (HAV) infection is a notifiable disease in Ireland, with national coverage of clinical and laboratory surveillance. In December 2020, a cluster of 11 HAV cases among the Irish Traveller community was detected. The outbreak investigation identified 61 total HAV cases from September 2020 to November 2021. Sequenced isolates were sub-genotype IA with identical genome sequence. Case-patients were predominantly aged under 18 (77%), hospitalised (46%) and lived on communal residential sites. Mass onsite HAV vaccination was employed following failure of initial ring vaccination to contain the outbreak. This is the largest outbreak of HAV described in Ireland, involving spillover to the UK and Netherlands. We recommend mass HAV vaccination and tailored communication for outbreak control in migratory subpopulations.