Factsheet about hepatitis A

factsheet facts

Hepatitis A is an acute infection of the liver caused by a small, non-enveloped hepatotropic virus classified in the genus Hepatovirus within the family Picornaviridae.

The pathogen

The genome of the hepatitis A virus (HAV) consists of a 7 500-nucleotide linear, positive-stranded RNA. Genotypes have been traditionally defined based on the analysis of a 168-nucleotide segment of the VP1-2A region. Based on this sequence, six HAV genotypes, from I to VI, have been defined. Genotypes I, II and III, divided into subtypes A and B, infect humans. Data on genotype distribution showed that genotype I is the most prevalent worldwide, with IA being reported more frequently than IB, and that sub-genotype IIIA is prevalent in central Asia. In areas of low endemicity, such as the United States and Western Europe, sub-genotype IA dominates, but all genotypes and subtypes have been reported [1].

Clinical features

The disease is often asymptomatic or mild, particularly in children under five years. In adults, the onset of illness is usually abrupt with fever, malaise and abdominal discomfort. Jaundice is the predominant symptom. Symptoms may last from one or two weeks to months. Prolonged, relapsing hepatitis for up to one year occurs in 15% of cases. No chronic infection is known to occur and infection confers lifelong immunity [2].
The case-fatality ratio is low (0.1–0.3%) but might be higher (1.8%) in adults over 50 years of age or persons with underlying chronic liver disease [2,3].

Transmission

Hepatitis A is highly transmissible and has an average incubation period of 28 to 30 days (range 15–50 days). The maximum infectivity is during the second half of the incubation period (i.e. while asymptomatic) and most cases are considered non-infectious after the first week of jaundice.

HAV can be transmitted through contaminated water, food and via the faecal–oral route among close contacts (e.g. household contacts, sexual contacts, day-care centres or schools) [4-6]. The following risk factors or risk groups have also been associated with illness in outbreaks: use of contaminated blood products [7], people who inject drugs [8-10] or use other illicit drugs [11], men having sex with men (MSM) [4], and homeless people [11,12]

The virus is very resistant in the environment as well as to several preservation methods used in the food industry, e.g. acidification or freezing [13-18], thus possible food-borne transmission should be investigated when several cases are reported within a short time period.

Diagnostic methods

The laboratory diagnosis of hepatitis A can be made with specific serological tests for detection of anti-HAV antibodies. Anti-HAV IgM antibodies are generally detectable from 4 weeks to 4–6 months after infection, rarely persisting for more than 12 months. Anti-HAV IgG and IgM antibodies can be detected simultaneously 1–2 weeks after the onset of symptom. Anti-HAV IgG are then detectable lifelong.

Molecular characterisation of the virus for epidemiological purposes is performed by comparative sequencing analysis of specific regions of the viral genome.

Case management and treatment

No pharmacological treatment exists, patients recover spontaneously.

Public health control measures

The main public health control measures for hepatitis A are assuring adequate sanitation and housing, education about sound personal hygiene practices, particularly hand hygiene, and pre-exposure immunisation of individuals in populations at increased risk.

Personal protection and prevention

Several inactivated vaccines are available for prevention, all showing very high efficacy. Active (antigen) and passive (antisera) immunisation is effective if administered within two weeks of exposure. Strict control measures, such as reinforcing personal hygiene, contact tracing and administration of vaccine to exposed persons, have proved to be effective [19,20].

 

References:

1. Desbois D, Couturier E, Mackiewicz V, Graube A, Letort MJ, Dussaix E, et al. Epidemiology and genetic characterization of hepatitis a virus genotype iia. Journal of Clinical Microbiology. 2010 Sep;48(9):3306-15. PubMed PMID: 20592136. Pubmed Central PMCID: 2937740.

2.  Heymann D. Control of Communicable Diseases Manual, 18th edition, Official Report of the American Public Health Association 2008.

3. Koff RS. Hepatitis A. Lancet. 1998 May 30;351(9116):1643-9. PubMed PMID: 9620732.

4.  Blystad H, Kløvstad H, Stene-Johansen A, Steen T. Hepatitis A outbreak in men who have sex with men, Oslo and Bergen in Norway. Euro Surveillance. 2004;8(43).

5. Hanna JN, Humphreys JL, Hills SL, Richards AR, Brookes DL. Recognising and responding to outbreaks of hepatitis A associated with child day-care centres. Australian and New Zealand Journal of Public Health. 2001 Dec;25(6):525-8. PubMed PMID: 11824988.

6. Pebody RG, Leino T, Ruutu P, Kinnunen L, Davidkin I, Nohynek H, et al. Foodborne outbreaks of hepatitis A in a low endemic country: An emerging problem? Epidemiology and Infection. 1998 Feb;120(1):55-9. PubMed PMID: 9528818. Pubmed Central PMCID: 2809349.

7. Vonberg RP, Gastmeier P. Hospital-acquired infections related to contaminated substances. The Journal of Hospital Infection. 2007 Jan;65(1):15-23. PubMed PMID: 17145102.

8. Ngui SL, Granerod J, Jewes LA, Crowcroft NS, Teo CG. 2002 Hepatitis A Outbreaks Investigation Network. Outbreaks of hepatitis A in England and Wales associated with two co-circulating hepatitis a virus strains. Journal of Medical Virology. 2008 Jul;80(7):1181-8. PubMed PMID: 18461630.

9. O'Donovan D, Cooke RP, Joce R, Eastbury A, Waite J, Stene-Johansen K. An outbreak of hepatitis A amongst injecting drug users. Epidemiology and Infection. 2001 Dec;127(3):469-73. PubMed PMID: 11811880. Pubmed Central PMCID: 2869772.

10. Widell A, Hansson BG, Moestrup T, Nordenfelt E. Increased occurrence of hepatitis A with cyclic outbreaks among drug addicts in a Swedish community. Infection. 1983 Jul-Aug;11(4):198-200. PubMed PMID: 6618674.

11. James TL, Aschkenasy M, Eliseo LJ, Olshaker J, Mehta SD. Response to hepatitis A epidemic: Emergency department collaboration with Public Health Commission. The Journal of Emergency Medicine. 2009 May;36(4):412-6. PubMed PMID: 18359602.

12. Tjon GM, Gotz H, Koek AG, de Zwart O, Mertens PL, Coutinho RA, et al. An outbreak of hepatitis A among homeless drug users in Rotterdam, the Netherlands. Journal of Medical Virology. 2005 Nov;77(3):360-6. PubMed PMID: 16173016.

13. Baert L, Debevere J, Uyttendaele M. The efficacy of preservation methods to inactivate foodborne viruses. International Journal of Food Microbiology. 2009 May 31;131(2-3):83-94. PubMed PMID: 19349089.

14. Buisson Y, Van Cuyck-Gandre H, Deloince R. [water and viral hepatitis]. Bulletin de la Societe de pathologie exotique. 1993;86(5 Pt 2):479-83. PubMed PMID: 7819806. L'eau et les hepatites virales.

15. Butot S, Putallaz T, Sanchez G. Effects of sanitation, freezing and frozen storage on enteric viruses in berries and herbs. International Journal of Food Microbiology. 2008 Aug 15;126(1-2):30-5. PubMed PMID: 18547667.

16. Gerba CP, Kennedy D. Enteric virus survival during household laundering and impact of disinfection with sodium hypochlorite. Applied and Environmental Microbiology. 2007 Jul;73(14):4425-8. PubMed PMID: 17526793. Pubmed Central PMCID: 1932823.

17. John DE, Rose JB. Review of factors affecting microbial survival in groundwater. Environmental Science & Technology. 2005 Oct 1;39(19):7345-56. PubMed PMID: 16245801.

18. Webert KE, Cserti CM, Hannon J, Lin Y, Pavenski K, Pendergrast JM, et al. Proceedings of a consensus conference: Pathogen inactivation-making decisions about new technologies. Transfusion medicine reviews. 2008 Jan;22(1):1-34. PubMed PMID: 18063190

19. Latimer WW, Moleko AG, Melnikov A, Mitchell M, Severtson SG, von Thomsen S, et al. Prevalence and correlates of hepatitis A among adult drug users: The significance of incarceration and race/ethnicity. Vaccine. 2007 Oct 10;25(41):7125-31. PubMed PMID: 17766016.

20. Sunthornchart S, Linkins RW, Natephisarnwanish V, Levine WC, Maneesinthu K, Lolekha R, et al. Prevalence of hepatitis B, tetanus, hepatitis A, human immunodeficiency virus and feasibility of vaccine delivery among injecting drug users in Bangkok, Thailand, 2003-2005. Addiction. 2008 Oct;103(10):1687-95. PubMed PMID: 18705685.