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 morality. 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. Epidemic related to contaminated food or water can erupt explosively, such as the epidemic in Shanghai in 1988 that affected about 300,000 people. 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.
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 in frequent, 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, diarrhea, 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 order 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
- Lake of safe water
- Injection drugs
- Living in a household with an infected person
- Being a sexual partner of someone with acute hepatitis A infection
- 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 trascriptase polymerase chain reaction (RT-PCR) to detect the hepatitis A virus RNA, but may require specialished 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 edequate nutritional balance, including replacement of fluids that are lost from vomiting and diarrhorea.
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
- 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 dose 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 people at increased risk of hepatitis A, including:
- Travellers to countries where the virus is endemic
- Men who have six with men
- 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 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.
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