Abstract
Hepatitis A Virus (HAV) infects millions of individuals annually and is a major cause of acute viral hepatitis worldwide. This study aims to (1) assess HAV infection in suspected acute hepatitis patients at public healthcare institutions in Brazil; (2) evaluate the proportion of immunized individuals against HAV; (3) identify HAV genotypes; (4) examine the association between HAV infection and demographic data, as well as exposure to risk factors. This is a prospective, observational multicenter study conducted in primary health services in Brazil from October 2019 to May 2023, involving 1721 patients with suspected acute hepatitis. Acute HAV infection was identified in 108 (6.3%) patients, predominantly in young men (80%) and from South and Southeast regions of Brazil (97%). Anti-HAV IgG, indicating previous exposure or vaccination, was detected in 78.6% of individuals (74% in the South to 91% in the North). Genotype I.A was found in all cases and approximately 450 mutations were identified, most of them in the structural proteins VP1-3. Two viral groups were identified and related to two introductions of the virus: cosmopolitan sequences from North America, South America, and Europe, and a minor group of Brazilian sequences similar to Asian and South American ones. The high incidence of acute HAV infections highlights the need for targeted prevention and vaccination strategies. The characterization of HAV genetic diversity and molecular epidemiology contributes to monitoring and identifying emerging outbreaks.