Hepatitis A: Immune response and virus evolution

Abstract

Hepatitis A (HA) is the most common form of acute hepatitis worldwide [1]. The HA etiological agent is the hepatitis A virus (HAV), an enteric virus primarily transmitted through the fecal-oral route [2]. The distribution of HA in different geographical areas of the world has been associated with socioeconomic development and access to clean water and sanitation [1-3]. The incidence of HAV infection is high in developing regions and low in developed regions [2]. In developing countries, most individuals are exposed to HAV during early childhood, when the infection is primarily asymptomatic. In developed countries, infection typically occurs at an older age associated with more severe clinical symptoms. Because HAV infection induces life-long immunity, severe HA is rare in adults of highly endemic regions. In contrast, HA in low endemic areas primarily occurs in immunologically naïve adults who come in contact with the virus while travelling to endemic regions [4, 5], have risky sexual practices [6, 7], or consume contaminated water or food [8-10].