- Hepatitis A is a viral liver disease that can cause mild to severe illness.
- The hepatitis A virus is transmitted through ingestion of contaminated food and water or through direct contact with an infectious person.
- Almost everyone recovers fully from hepatitis A, but very small proportions die from fulminant hepatitis.
- Hepatitis A infection risk is associated with a lack of safe water and poor sanitation.
- Epidemics can be explosive and cause significant economic loss.
- Improved sanitation and the hepatitis A vaccine are the most effective ways to combat the disease.
Hepatitis A is a liver disease caused by the hepatitis A virus. The virus is primarily spread when an uninfected (and unvaccinated) person ingests food or water that is contaminated with the faeces of an infected person. The disease is closely associated with unsafe water, inadequate sanitation and poor personal hygiene.
Unlike hepatitis B and C, hepatitis A infection does not cause chronic liver disease and is rarely fatal, but it can cause debilitating symptoms and fulminant hepatitis (acute liver failure), which is associated with high mortality.
Hepatitis A occurs sporadically and in epidemics worldwide, with a tendency for cyclic recurrences. The hepatitis A virus is one of the most frequent causes of foodborne infection. Epidemics related to contaminated food or water can erupt explosively, such as the epidemic in Shanghai in 1988 that affected about 300 000 people1. Hepatitis A viruses persist in the environment and can withstand food-production processes routinely used to inactivate and/or control bacterial pathogens.
The disease can lead to significant economic and social consequences in communities. It can take weeks or months for people recovering from the illness to return to work, school or daily life. The impact on food establishments identified with the virus, and local productivity in general, can be substantial.
Geographical distribution areas can be characterized as having high, intermediate or low levels of hepatitis A infection.
Areas with high levels of infection
In developing countries with very poor sanitary conditions and hygienic practices, most children (90%) have been infected with the hepatitis A virus before the age of 10 years2. Those infected in childhood do not experience any noticeable symptoms. Epidemics are uncommon because older children and adults are generally immune. Symptomatic disease rates in these areas are low and outbreaks are rare.
Areas with intermediate levels of infection
In developing countries, countries with transitional economies and regions where sanitary conditions are variable, children often escape infection in early childhood. Ironically, these improved economic and sanitary conditions may lead to a higher susceptibility in older age groups and higher disease rates, as infections occur in adolescents and adults, and large outbreaks can occur.
Areas with low levels of infection
In developed countries with good sanitary and hygienic conditions, infection rates are low. Disease may occur among adolescents and adults in high-risk groups, such as injecting-drug users, men who have sex with men, people travelling to areas of high endemicity, and in isolated populations, such as closed religious communities.
The hepatitis A virus is transmitted primarily by the faecal-oral route; that is when an uninfected person ingests food or water that has been contaminated with the faeces of an infected person. Waterborne outbreaks, though infrequent, are usually associated with sewage-contaminated or inadequately treated water.
The virus can also be transmitted through close physical contact with an infectious person, although casual contact among people does not spread the virus.
The incubation period of hepatitis A is usually 14–28 days.
Symptoms of hepatitis A range from mild to severe, and can include fever, malaise, loss of appetite, diarrhoea, nausea, abdominal discomfort, dark-coloured urine and jaundice (a yellowing of the skin and whites of the eyes). Not everyone who is infected will have all of the symptoms.
Adults have signs and symptoms of illness more often than children, and the severity of disease and mortality increases in older age groups. Infected children under 6 years of age do not usually experience noticeable symptoms, and only 10% develop jaundice. Among older children and adults, infection usually causes more severe symptoms, with jaundice occurring in more than 70% of cases.
Who is at risk?
Anyone who has not been vaccinated or previously infected can contract hepatitis A. In areas where the virus is widespread (high endemicity), most hepatitis A infections occur during early childhood. Risk factors include:
- poor sanitation;
- lack of safe water;
- injecting drugs;
- living in a household with an infected person;
- being a sexual partner of someone with acute hepatitis A infection; and
- travelling to areas of high endemicity without being immunized.
Cases of hepatitis A are not clinically distinguishable from other types of acute viral hepatitis. Specific diagnosis is made by the detection of HAV-specific IgM and IgG antibodies in the blood. Additional tests include reverse transcriptase polymerase chain reaction (RT-PCR) to detect the hepatitis A virus RNA, but may require specialised laboratory facilities.
There is no specific treatment for hepatitis A. Recovery from symptoms following infection may be slow and may take several weeks or months. Therapy is aimed at maintaining comfort and adequate nutritional balance, including replacement of fluids that are lost from vomiting and diarrhoea.
Improved sanitation, food safety and immunization are the most effective ways to combat hepatitis A.
The spread of hepatitis A can be reduced by:
- adequate supplies of safe drinking water;
- proper disposal of sewage within communities; and
- personal hygiene practices such as regular hand-washing with safe water.
Several hepatitis A vaccines are available internationally. All are similar in terms of how well they protect people from the virus and their side-effects. No vaccine is licensed for children younger than 1 year of age.
Nearly 100% of people develop protective levels of antibodies to the virus within 1 month after a single dose of the vaccine. Even after exposure to the virus, a single dose of the vaccine within 2 weeks of contact with the virus has protective effects. Still, manufacturers recommend two vaccine doses to ensure a longer-term protection of about 5 to 8 years after vaccination.
Millions of people have been immunized worldwide with no serious adverse events. The vaccine can be given as part of regular childhood immunizations programmes and also with other vaccines for travellers.
Vaccination against hepatitis A should be part of a comprehensive plan for the prevention and control of viral hepatitis. Planning for large-scale immunization programmes should involve careful economic evaluations and consider alternative or additional prevention methods, such as improved sanitation, and health education for improved hygiene practices.
Whether or not to include the vaccine in routine childhood immunizations depends on the local context. The proportion of susceptible people in the population and the level of exposure to the virus should be considered. Several countries, including Argentina, China, Israel, Turkey, and the United States of America have introduced the vaccine in routine childhood immunizations.
While the 2 dose regimen of inactivated hepatitis A vaccine is used in many countries, other countries may consider inclusion of a single-dose inactivated hepatitis A vaccine in their immunization schedules. Some countries also recommend the vaccine for people at increased risk of hepatitis A, including:
- travellers to countries where the virus is endemic;
- men who have sex with men; and
- people with chronic liver disease (because of their increased risk of serious complications if they acquire hepatitis A infection).
Regarding immunization for outbreak response, recommendations for hepatitis A vaccination should also be site-specific. The feasibility of rapidly implementing a widespread immunization campaign needs to be included.
Vaccination to control community-wide outbreaks is most successful in small communities, when the campaign is started early and when high coverage of multiple age groups is achieved. Vaccination efforts should be supplemented by health education to improve sanitation, hygiene practices and food safety.
WHO is working in the following areas to prevent and control viral hepatitis:
- raising awareness, promoting partnerships and mobilizing resources;
- formulating evidence-based policy and data for action;
- preventing transmission; and
- executing screening, care and treatment.
WHO also organizes World Hepatitis Day on July 28 every year to increase awareness and understanding of viral hepatitis.
1 Halliday ML1, Kang LY, Zhou TK, Hu MD, Pan QC, Fu TY, Huang YS, Hu SL. An epidemic of hepatitis A attributable to the ingestion of raw clams in Shanghai, China. J Infect Dis. 1991 Nov;164(5):852-9.
2 Jacobsen KH, Wiersma ST. Hepatitis A virus seroprevalence by age and world region, 1990 and 2005. Vaccine 28 (2010) 6653–6657.