Hepatitis A Virus

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.

Keywords: picornavirus; hepatovirus; jaundice; faecal–oral transmission; liver disease; vaccine

Figure 1. Electron micrograph of purified hepatitis A virus. (Magnification ×165 000.)
Figure 2. Hepatitis A virus genome. The top line indicates the nucleotide (NT) number and the orientation of the positive‐stranded RNA genome. The P1, P2 and P3 genome regions are indicated under this scale. The individual viral proteins are depicted within or above the rectangles, with common names for the capsid polypeptides shown below the respective locations. The covalently coupled VPg is shown by the circle at the extreme 5′‐end of the genome, while the polypyrimidine tract (pY1) and the location of the internal ribosomal entry site (IRES) structures are depicted by the hatched boxes. Viral protease cleavage sites are shown within the lower rectangle. The bold arrow indicates the primary cleavage site; solid line arrows indicate cleavage sites identified experimentally, while dotted line arrows indicate predicted cleavage sites. A, alanine; Q, glutamine; M, methionine; V, valine; T, threonine; S, serine; G, glycine; R, arginine; UTR, untranslated region.
Figure 3. Time course of a typical hepatitis A virus (HAV) infection. Ig, immunoglobulin.
Figure 4. Worldwide seroprevalence patterns of hepatitis A virus (HAV) infection endemicity. A country's endemicity of infection has been generalised from best available data and may vary within parts of the country. Green, very low endemicity; orange, low endemicity; yellow, intermediate endemicity; pink, high endemicity.
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Further Reading

Centers for Disease Control (2006) Prevention of Hepatitis A Through Active or Passive Immunization: Recommendations of the Advisory Committee on Immunization Practices (ACIP). Morbidity and Mortality Weekly Report 45 (No. RR‐7): 1–23.

Cowie B and Locarnini SA (2014) Hepatitis A virus: epidemiology and prevention. In: Thomas HC , Lock ASF , Locarnini SA and Zuckerman AJ (eds) Viral Hepatitis, 4th edn, vol. 1, pp. 43–62. West Sussex, UK: Wiley Blackwell.

Feng Z and Lemon SM (2010) Pathogenesis of hepatitis A virus infection. In: Domingo E , Ehenfeld E and Roos R (eds) The Picornaviruses: Molecular Biology, Evolution and Pathogenesis, pp. 383–396. Washington DC: American Society of Microbiology Press.

Hollinger FB and Martin A (2013) Hepatitis A virus. In: Fields BN , Knipe DM , Howley PM , et al. (eds) Fields Virology, 6th edn, vol. 1, pp. 550–581. Philadelphia: Lippincott‐Raven.

Kaplan GG , Konduru K , Manangeeswaran M , et al. (2014) Hepatitis A virus: structure, molecular virology, natural history, and experimental models. In: Thomas HC , Lock ASF , Locarnini SA and Zuckerman AJ (eds) Viral Hepatitis, 4th edn, vol. 1, pp. 27–42. West Sussex, UK: Wiley Blackwell.

Rios AM (2014) Hepatitis A virus. In: Cherry JD , Harrison GJ , Kaplan SL , Steinbach WJ and Hotez PJ (eds) Feigin and Cherry's Textbook of Pediatric Infectious Diseases, 7th edn, pp. 2128–2147. Philadelphia: WB Saunders.

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How to Cite close
Feng, Zongdi(May 2017) Hepatitis A Virus. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001026.pub2]