First evidence for continuous circulation of hepatitis A virus subgenotype IIA in Central Africa

Although a high seroprevalence of antibodies against hepatitis A virus (HAV) has been estimated in Central Africa, the current status of both HAV infections and seroprevalence of anti‐HAV antibodies remains unclear due to a paucity of surveillance data available. We conducted a serological survey during 2015‐2017 in Gabon, Central Africa, and confirmed a high seroprevalence of anti‐HAV antibodies in all age groups. To identify the currently circulating HAV strains and to reveal the epidemiological and genetic characteristics of the virus, we conducted molecular surveillance in a total of 1007 patients presenting febrile illness. Through HAV detection and sequencing, we identified subgenotype IIA (HAV‐IIA) infections in the country throughout the year. A significant prevalence trend emerged in the young child population, presenting several infection peaks which appeared to be unrelated to dry or rainy seasons. Whole‐genome sequencing and phylogenetic analyses revealed local HAV‐IIA evolutionary events in Central Africa, indicating the circulation of HAV‐IIA strains of a region‐specific lineage. Recombination analysis of complete genome sequences revealed potential recombination events in Gabonese HAV strains. Interestingly, Gabonese HAV‐IIA possibly acquired the 5’‐untranslated region (5’‐UTR) of the rare subgenotype HAV‐IIB in recent years, suggesting the present existence of HAV‐IIB in Central Africa. These findings indicate a currently stable HAV‐IIA circulation in Gabon, with a high risk of infections in children aged under 5 years. Our findings will enhance the understanding of the current status of HAV infections in Central Africa and provide new insight into the molecular epidemiology and evolution of HAV genotype II.