Hepatitis A HAV

Organism Infectious hepatitis is a viral infection caused by a member of the Picorna-viridae, which includes both enteroviruses and rhinoviruses.

Clinical features The main pathology is inflammation, infiltration and necrosis of the liver, resulting in biliary stasis and jaundice. The infection generally starts insidiously, the person feels lethargic, anorexic and depressed. Fever, vomiting, diarrhoea and abdominal discomfort ensue before the appearance of jaundice reveals the diagnosis. Once jaundice appears, the person generally starts to feel better. Hepatitis A is a mild disease leading to spontaneous cure in the large majority, with only a few cases developing acute fulminant hepatitis and even rarely severe chronic liver damage. There is an increase in symptomatic and severe cases with increasing age.

Diagnosis is made on clinical grounds and by the demonstration of IgM antibodies to HAV (IgM anti-HAV) in serum.

Transmission The early case is highly infectious contaminating food and water. Infection can also be transmitted directly from poor personal hygiene such as by hand-shaking. Intra-familial transmission is the commonest pattern generally due to contamination of food and utensils by a food handler, but large epidemics can occur where a person in the early stages of the illness prepares community food. Because of its insidious nature, the disease is not generally recognized until jaundice appears, by which time infection may have been widely transmitted.

Hepatitis is mainly a disease of poor sanitation, with water and food as the principal vehicles of transmission, but can also occur when sanitation is good. Salads, cold meats and raw sea food are common vehicles of transmission.

The carrier state is not important, but a large number of asymptomatic cases are produced. Epidemics occur when sewage contaminates water supplies producing infection in people who have previously acquired some immunity, suggesting that the disease may be dose-dependent. Where there is a large infecting inoculum, infection can occur despite previous experience of the disease. Chimpanzees and other animals have been found infected, but probably have no epidemiological significance.

Incubation period is 15-50 days, generally about 28 days.

Period of communicability is the later half of the incubation period until about 1 week after jaundice appears, so that most cases have already transmitted the virus to family and contacts before they report for medical attention.

Occurrence and distribution Hepatitis is endemic in most tropical countries, with children coming into contact early in life and developing a degree of immunity. Nonimmune persons, such as from an area of good sanitation coming into this environment, are likely to develop the disease. Epidemics occur in developed countries, especially in institutions, such as schools and prisons, due to poor food hygiene.

Control and prevention During an outbreak of hepatitis A, extra effort should be made to encourage scrupulous personal hygiene with hand-washing. Anybody who starts to feel unwell should be temporarily relieved of preparing food. In an epidemic situation, search should be made for the origin of the outbreak and preventive measures taken. In the long term, water supplies and sanitation should be upgraded.

HAV vaccine protects the individual at risk and should be mandatory for those going from an area of good sanitation to one of poor sanitation, such as tourists and expatriates. Two doses are required to be given 6-18 months apart, although one dose still gives high levels of immunity. Immunity from a two-dose regime may be lifelong, but a booster at 10 years is currently recommended. As most of the population in an endemic area would have met the infection as children and either had no symptoms or just a mild infection, there is no case for mass vaccination, except for high-risk groups.

Treatment There is no specific treatment and supportive measures should be undertaken. Fatty foods should be avoided and a good fluid intake maintained.

Surveillance Once hepatitis has been detected, health authorities should notify central authorities and surrounding areas.

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