Hepatitis A Virus

Abstract

Abstract Hepatitis A virus (HAV) is one of the five human hepatitis viruses that replicate in and cause inflammation of the liver. HAV is transmitted through a faecal–oral route and has a unique life cycle in that it is shed as naked virions into the faeces but circulates in an enveloped form in the blood. In addition, the virus has several unique mechanisms to evade detection by the host immune system. The majority of HAV infections are self‐limited and asymptomatic, but severe forms sometimes occur, particularly in the elderly. HAV has only one serotype, and persons infected with HAV usually develop lifelong immunity. Incidence rates of HAV infections have been greatly reduced owing to improved sanitation and the use of very successful vaccines. Key Concepts The hepatitis A virus is transmitted via the faecal–oral route and is a major cause of acute hepatitis worldwide. HAV only infects humans and non‐human primates, although HAV‐like viruses infect a range of animal species. HAV infection is extraordinary ‘stealthy’, and the virus has multiple mechanisms to evade the host immune response. HAV is shed as naked virions in the faeces but circulates as quasi‐enveloped virions in the blood. Hepatitis A vaccine is one of the most successful vaccines ever developed, providing lifelong protection when given either pre‐exposure or post‐exposure.