Hepatitis B HBV

Organism Hepatitis B virus (HBV).

Clinical features In many parts of the developing world, HBV infection is common, but only about 30% show any symptoms. However, these symptomatic cases present as a more severe disease than hepatitis A, with a persistent jaundice, often resulting in liver damage.

After an insidious onset with anorexia, nausea and abdominal discomfort, jaundice then develops, from which the patient either recovers or goes on to develop chronic active disease. Low-grade infection continues with periods of jaundice alternating with remissions, but invariably cirrhosis develops. The disease is more serious in those over 40 years of age, in pregnant women and newborn infants. Hepatocellu-lar carcinoma is associated with chronic hepatitis B infection.

Diagnosis can be made by finding the surface antigens (HBs Ag). There are four subtypes adw, ayw, adr and ayr, which vary in their geographical distribution providing useful epidemiological markers. A further antigen e (HBe Ag) is a marker of increased infectivity as well as indicating active viral replication in hepatocytes (which may result in liver damage).

Transmission can occur from blood, serum, saliva and seminal fluid. It is a hazard of blood transfusions, renal dialysis, injections and tattooing. It can be transmitted by sexual intercourse and during delivery. The virus has been found in some blood-sucking insects (e.g. bed bugs), but transmission by this means has not been shown to occur.

Certain people are more infectious than others resulting in a carrier state, with the period of communicability being considerable. The risk of an infant becoming infected from a carrier mother can be 50-70% in some ethnic groups. There is a greater likelihood of the mother passing on the infection if she has acute hepatitis B in the second or third trimester or up to 2 months after delivery. A high titre of surface e antigen or a history of transmission to previous children increases the risk of a mother infecting her infant. The carrier state is more common in males and in those that acquired their infection in childhood.

Incubation period 6 weeks to 6 months (usually 9-12 weeks), a larger inoculum of virus probably resulting in a shorter incubation period.

Period of communicability From several weeks before the onset of symptoms, continuing until the end of clinical disease, unless the person becomes a carrier in which case it is life long.

Occurrence and distribution The carrier state has been estimated to be present in over 350 million people with varying rates in different parts of the world: Western Europe, 1%; South and Central America 2-7%; and Africa, Asia and Western Pacific, >8%. Infection is thought to occur commonly in infancy or early childhood in the more endemic areas.

Control and prevention Hepatitis B vaccine can be given to those at risk and as part of the EPI programme. If given before infection, it prevents the development of disease and the carrier state. Ideally, Hepatitis B vaccine is given at the same time as DTP, but in countries where perinatal transmission is common, such as in Southeast Asia, a dose at birth is recommended. Immunity is thought to last for at least 15 years in the fully vaccinated. There is convincing evidence that reduction of carriers can prevent the development of primary liver cell cancer.

Preventive methods are strict aseptic precautions in giving blood transfusions, injections and the handling of blood. All blood donors should be screened with contributions to pooled blood being particularly scrutinized. The control of STIs has been covered above. Homosexual practice is particularly liable to lead to HBV infection. Persons at risk should be vaccinated.

Treatment There is no specific treatment, but alpha-interferon and lamivudine have a limited effect in some people, particularly in the early stage of infection. Long-term treatment may also be of value.

Surveillance As with HIV infection, blood obtained in antenatal clinics, STI clinics or for other purposes can be anonymously tested for HbsAg. Surveys in developing countries demonstrated the high levels of carriers, so with the implementation of routine vaccination, follow-up surveys will monitor the effectiveness of the vaccination programmes.

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