Genomic Epidemiology of Resurgent Hepatitis A in Florida, 2018-2022

During 2018-2022, a resurgence of hepatitis A occurred in Florida, with 5491 cases reported. Genotyping was performed on a convenience sample of cases through amplification and sequencing of the hepatitis A virus VP1-P2B junction region. Virus isolates from 1190 cases (22%) were genotyped; 69% were subgenotype IB, 30% were subgenotype IA, and 1% were subgenotype IIIA. Subgenotype IB was more common among patients reporting recent drug use or homelessness, whereas IA was more common among those reporting recent international travel and among men who have sex with men. Genotype IB infection was associated with a more than 4-fold greater odds of death compared to IA infection. A network analysis revealed 11 genomic clusters of ≥10 cases, with distinct temporal and spatial distributions. Case reports in 2023 decreased to below pre-2018 numbers, likely due to high population immunity following natural infection and extensive vaccination activities in the highest-risk groups.