Hepatitis A virus

Abstract

Four hundred years B.C., Hippocrates described an illness characterized by episodes of jaundice that could probably correspond to a viral hepatitis. Two thousand three hundred years later, at the beginning of the 20th century, the term ‘infectious hepatitis’ was defined and associated to a kind of infectious jaundice occurring in epidemics. In the early 40's two separate entities were identified ‘infectious’ and ‘serum’ hepatitis. The ‘infectious’ type corresponds to those hepatitis syndromes transmitted through the faecal-oral route, or enteric hepatitis and the ‘serum’ hepatitis to those parenterally transmitted. The enteric hepatitis agents which can be foodborne and waterborne include hepatitis A and E viruses. The present chapter will focus on hepatitis A and its causative agent the hepatitis A virus (HAV). In spite of an efficient vaccine and improved hygiene conditions, hepatitis A is still the most common viral hepatitis worldwide. Large foodborne outbreaks are still of major concern causing hundreds of cases and huge economic losses in the present context of global food trade. Hepatitis A virus is a unique picornavirus with many differences in its molecular biology including both its incapacity to induce the inhibition of the cellular protein synthesis and a genomic composition and genome structure that have evolved to render an extremely quiescent replication phenotype through a very slow translation pace of the genomic region encoding the capsid protein which in turn is necessary to ensure an accurate capsid folding. Such proper capsid folding is critical to warrant a high environmental stability, important for a virus transmitted through the faecal-oral route with long extracorporeal periods. HAV capsid is subjected to many biological and environmental constraints during virus transmission which may contribute to a very low antigenic variability. However, the inherent genetic variability of an RNA virus in association with vaccination campaigns may promote the emergence of new variants.