China has one of the highest rates of hepatitis B virus (HBV) endemicity in the world. In a survey of five provinces, the overall HBV infection rate in the general population was found to be 42.6%, with 10.3% testing positive for hepatitis B surface antigen (HBsAg). Higher rates were found in rural than in urban areas. The prevalence of HBsAg among children under 1 year of age is quite low but increases rapidly thereafter, reaching a peak among 5 to 9 year olds. The pattern of age distribution suggests that horizontal transmission is an important route of HBV infection during early childhood, and the proportion of chronic HBsAg carriage attributable to perinatal transmission has been estimated at only 13-20%. Contact with infected family members probably accounts for much of the horizontal transmission in children. In a nationwide survey, 27.2% of families were found to have one or more HBsAg positive members and a strong tendency for family clustering has been identified. The strategy for prevention of HBV infection includes vaccination of all newborns, whether their mothers are HBsAg positive or negative, together with vaccination of high risk populations, and improved control measures in clinics and blood transfusion centres.

Hepatitis B remains one of the most important infectious diseases in China. In 1980, an overall hepatitis B virus (HBV) infection rate of 42.6% was reported and a hepatitis B surface antigen (HBsAg) carrier rate of 10.3%. HBsAg positivity among children under 1 year of age ranged from 5.1% in Beijing to 7% in Guangdong. A peak in carrier rate was observed in 7 to 14 year olds, reaching 24% in Guangdong. During the past decade, there has been no significant change in overall HBV carrier rates. However, in areas where hepatitis B vaccination for all neonates has been introduced, a decline in HBsAg positivity in lower age groups has been observed. Perinatal transmission is believed to account for 35-50% of carriers although horizontal transmission is also important, particularly within families. Infants born to HBeAg positive carrier mothers are at even greater risk of infection. HBV infection during childhood leads to an increased risk of serious longterm sequelae, including hepatocellular carcinoma (HCC). It is hoped that universal childhood immunisation will allow control of HBV infections in China within a few generations.

The carrier rate of hepatitis B virus (HBV) in black Africans averages 10.4% throughout the continent. Even within each country, however, there may be wide variations. HBV carriage in black Africans is largely established in early childhood, mostly through horizontal transmission. Perinatal transmission also occurs but to a much lesser extent than in the Far East. For unknown reasons, HBeAg positivity rates are much lower in black Africans of childbearing age than in women in the Far East. Universal HBV vaccination of infants in South Africa started in April 1995. Effective integration into the Expanded Programme on Vaccination will probably be necessary if administration of second and third doses is to be ensured. Fortunately, a natural process of urbanisation is also having a beneficial effect on the black carrier rate in South Africa, as urban carrier rates tend to be much lower than those in rural area. Within the next 20 years, therefore, there should be a great reduction in the numbers of acute HBV infections and new carriers. However, it will take much longer before there is any substantial impact on the burden of the longterm sequelae of HBV infection--that is, cirrhosis and hepatocellular carcinoma.

In the United States, the reported rate of hepatitis B has declined by over 50% since 1987, probably as a result of vaccination programmes, behavioural changes, refinements in blood screening procedures, and the availability of virus inactivated blood components. The majority of new hepatitis B infections occur in 20-39 year olds, and perinatal transmission is uncommon except in certain at risk groups. Initial efforts to control hepatitis B in the US were targeted at high risk groups, including health care personnel. Then, in 1988, the Centers for Disease Control and Prevention (CDC) recommended screening of all pregnant females for hepatitis B surface antigen and full immunisation of infants born to those testing positive. A recommendation for universal immunisation of infants was endorsed in 1991. Compliance has been slow but progressive. The CDC also has recommended 'catch up' immunisation of adolescents and high risk children and adults. Demonstration projects suggest that these can be successful, given the provision of free or low cost vaccine and appropriate support. Hepatitis B vaccination has been shown to be cost effective and should be integrated into the routine childhood immunisation schedule. Responses to hepatitis B vaccine have largely been shown to be durable, although at least one booster dose after five to 10 years seems prudent, especially if a low dose, yeast derived vaccine has been used.

Postnatal horizontal transmission of hepatitis B virus (HBV) in early childhood seems to be the predominant method by which high hepatitis B carrier rates in the Middle East are maintained. The prevalence of hepatitis B surface antigen (HBsAg) positive status among siblings of HBV carriers is similar during childhood and adulthood, suggesting that childhood intrafamilial transmission patterns persist into adult life. There is a tendency for asymptomatic HBV carriers to have higher alanine aminotransferase (ALT) values, a feature that also tends to cluster in families. Infection in the first five years of life contributes most to the case load of chronic liver disease and thus to mortality from HBV. Mass hepatitis B immunisation programmes have been started, and while they may eventually reduce the HBV carrier state and liver disease loads significantly, prospects for total eradication of HBV in the near future are not good.

The Western Pacific and South East Asia regions are the largest and most populous of the six World Health Organisation regions and include more than 40 countries. More than 75% of the world's estimated 350 million carriers are located here. The region has therefore provided many insights into the epidemiology, natural history, and control of hepatitis B infection and has been home to the first national control programmes. Hepatitis B is hyperendemic in most countries of the region, with carrier rates ranging from 5-35% except in Australia, New Zealand, and Japan, where the mean carrier rate is less than 2%. Patterns of infection vary considerably from country to country, city to city, and even village to village, and can change with time. Most infections are acquired early in childhood or in early adult life. A variety of control measures are in place and many countries in the region have introduced widespread or universal childhood immunisation policies with significant success. While it is theoretically possible that hepatitis B infection could be eradicated by universal childhood immunisation, there are several biological and practical issues that make this extremely difficult, suggesting that, for the foreseeable future, control may be a more realisable goal.

Although Singapore is in an endemic region for hepatitis B infection, the hepatitis B carriage rate of 5-6% is relatively low. The highest positivity rates for hepatitis B surface antigen (HBsAg) are found in the paediatric age group, with another peak in 40-49 year olds. Studies suggest that, although perinatal transmission is an important route of infection, most children acquire the virus through horizontal transmission between family members. Viral replication continues at a high rate in young carriers and tends to slow down with increasing age. Up to 50% of hepatitis B carriers in Singapore have chronic hepatitis, shown by raised serum ALT values and liver histology, and about 10% are infected with the precore mutant virus. About 20% of carriers have cirrhosis. Among patients with HCC, up to 75% are HBsAg positive, of whom 45% are still viraemic. Mass vaccination against hepatitis B was introduced into Singapore on a voluntary basis in 1983, with compulsory vaccination of babies born to HBeAg positive mothers since 1985. The number of cases of acute hepatitis B has fallen by 60% between 1989 and 1995 although the problems of the longterm complications of chronic hepatitis B still need to be tackled.

Both hepatocellular carcinoma (HCC) and iron overload are important health problems in Africa. Chronic hepatitis B virus (HBV) infection is recognised as a major risk factor for HCC, but iron overload in Africans has not been considered in pathogenesis. Up to half the patients with HCC in Africa do not have any recognised risk factors such as preceding chronic HBV infection, and other risk factors remain unidentified. HCC is an important complication of HLA-linked haemochromatosis, an iron loading disorder found in Europeans. It is proposed that African iron overload might also be a risk factor for HCC.

Susceptibility to primary biliary cirrhosis (PBC) may be partly inherited although instances of PBC within families are only infrequently described. The records of 736 patients with PBC seen over a 25 year period were examined to identify those with a positive family history. Ten patients originating from eight families were identified, giving a frequency of 1.33%. They comprised mother and daughter pairs; in two families both mother and daughter had been seen at our clinic. The daughters presented at an earlier age, median 36 years (range 24-54), than the mothers, 52 years (50-81). During follow up one daughter (45 years) and six mothers have died (range 53-81 years) and two mothers and one daughter have had a transplant aged 57, 57, and 30 years respectively. It is concluded that familial PBC is not rare, that it is related to maternally inherited factors, and that disease tends to present earlier in the second generation.

A 51 year old woman with a two year history of ulcerative colitis developed a wide spread gastrointestinal non-Hodgkin's lymphoma of low grade malignancy (MALT-lymphoma) involving upper and lower gastrointestinal tract, spleen, and bone marrow. After chemotherapy, clinical symptoms improved and lymphocytic infiltrates disappeared. Thirty nine cases of ulcerative colitis and 22 cases of Crohn's disease complicated by gastrointestinal lymphomas reported in published works are reviewed. In inflammatory bowel diseases any dense lymphocytic infiltrates seen in biopsy specimens obtained from ulcerative colitis or Crohn's disease should be assessed to exclude gastrointestinal lymphoma.