"Hepatitis" means inflammation of the liver cells. There are many causes of hepatitis and viral infection is one of them. Others include alcohol, drugs, chemicals and hereditary disease.

The term "viral hepatitis" is commonly used for several clinically similar diseases that are etiologically and epidemiologically distinct. Symptoms include poor appetite, tiredness, nausea, vomiting, diarrhoea, fever, upper abdominal discomfort, jaundice and tea-coloured urine. Nowadays, at least 6 different agents have been identified, namely hepatitis A, B, C, D, E and G virus. Hepatitis A and E are spread by the faeco-oral route while hepatitis B, C, D and G are transmitted parenterally. In Hong Kong hepatitis A and B infection are more common than the others.

Hepatitis A
Hepatitis A is probably the most common of all hepatitis. It is transmitted by the faeco-oral route through contaminated food, drinks and shellfish. It has an incubation period of 2 to 6 weeks. Most patients have a complete recovery but in a few cases, the liver may be severely affected. Immunity is usually life-long and there is no chronic carrier state.

Prevention
Hepatitis A immunoglobulin only provides short-term protection. The protection period of Hepatitis A vaccine is still under investigation. Therefore the more practical way to prevent this disease and other similarly transmitted infections is to drink only boiled water and eat well-cooked food (100¢ºFEJ boiling water of 5 minutes can kill hepatitis A virus)

Hepatitis B
Infection by the hepatitis B virus (HBV) is extremely common in Hong Kong. Half of the local population has been infected by the virus. HBV is present in blood and body fluids of carriers and is spread in four ways: (i) blood contact, (ii) sexual contact, (iii) mother to infant transmission at or around the time of delivery, (iv) close intrafamily contact. It has an incubation period of 6 weeks to 6 months. The virus causes acute hepatitis which can be followed by chronic liver damage, including cirrhosis and liver cancer. Approximately 5-10 % of adults and 70-90% of infants infected are unable to clear the virus, thus becoming chronic carriers and serve as a source of infection to others.

Prevention
The most effective way of prevention is by hepatitis B vaccination. Newborn babies and pre-school children at or below the age of 6 can receive free vaccination service in all Maternal and Child Health Centres. Babies born to carrier mothers should receive an additional dose of hepatitis B immunoglobulin at birth. Health care workers are at higher risk of contracting HBV and should therefore be vaccinated.
Three doses of vaccine are necessary to ensure maximum protection. The basic schedule is as follows:
1st and 2nd dose: at an interval of 1 month.
2nd and 3rd dose: at an interval of 5 months.

Universal blood precautions should be taken to prevent transmission of HBV or other bloodborne pathogens. All wounds should be properly dressed. Wear disposable gloves before touching wounds. Equipments for acupuncture, tattooing and ear-piercing should be adequately sterilized. Do not share toothbrushes and razors. Limit the number of sexual partners and always practise safe sex.

Hepatitis C
Hepatitis C is mainly acquired by blood transfusion and sharing needles among injecting drug users. It can lead to severe chronic hepatitis and even liver cancer. Since July, 1991 the HK Red Cross Transfusion service has been screening all donated blood for hepatitis C antibody. In Hong Kong there is 0.2% of the population is estimated to be infected with hepatitis C. At present there is no effective vaccine to prevent hepatitis C infection.

Hepatitis D
Hepatitis D virus (HDV), also known as the Delta Agent, is transmitted by the same routes as HBV and is an important cause of acute and severe chronic hepatitis in many parts of the world but is uncommon in Asia. HDV is an incomplete viral particle which cannot reproduce in liver cells without the presence of HBV. In other words, effective prevention of hepatitis B will also prevent against hepatitis D.

Hepatitis E
Hepatitis E virus (HEV) like HAV, is transmitted by the faeco-oral route. It has been responsible for large outbreaks of infection in some developing countries. Hepatitis E infection is uncommon in Hong Kong. Vaccine is not yet available.

Hepatitis G
Hepatitis G virus is a newly found virus. It is uncommon in Hong Kong. The main route of transmission is by blood contact. The possibility of developing chronic hepatitis or liver cancer is still under study. Vaccine is not yet available.

Sources: Dept. of Health
CT/vn/No. 30 (Sep, 2002)