Factsheet about hepatitis A
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 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 .
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 .
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].
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 , people who inject drugs [8-10] or use other illicit drugs , men having sex with men (MSM) , 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.
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].
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