Horizontal transmission of hepatitis B virus

Decrease of hepatitis A and B virus infections in the population of Okinawa, Japan

In 1988 1282 serum samples were collected from healthy Japanese persons living on Hateruma Island (574 samples) and Iriomote Island (708 samples) in Okinawa, Japan. Serological markers of hepatitis B virus (HBV) infection [hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc) were investigated and the findings compared with samples taken in 1980 on Hateruma Island and in 1970 and 1980 on Iriomote Island. The samples collected in 1988 on Iriomote Island were also tested for antibody to hepatitis A virus (anti-HAV) and the findings compared with the results of the 1970 and 1980 surveys. The overall prevalence of HBsAg and anti-HBc was 3.7 and 64.8% for Hateruma Island and 3.8 and 44.9% for Iriomote Island. In both areas the overall prevalence of anti-HBc was lower than in 1980, the decrease being significant for the 10-19 year age group on Hateruma Island and the age groups under 39 years on Iriomote Island. The overall prevalence of anti-HAV had fallen to 50.9%. This remarkable decrease had occurred in children and young adults. These data suggest that Virus A (HAV) and HBV infections have dramatically decreased among children in Okinawa within the past 2 decades.

Horizontal or vertical transmission of hepatitis B virus? A serological survey in family members of hepatitis B carriers in Singapore

Hepatitis B serology was performed on 270 family members of 78 hepatitis B carriers and hepatitis B e antigen status determined in those found to be HBsAg positive. The mean age of index patients was 38 years (range 3-74) and that of family members was 28 years (range 1-71). 67 family members (25%) were HBsAg positive. The proportions of family members positive for HBsAg and those negative for HBsAg but positive for anti-HBs and/or anti-HBc were 25% and 20% for children, 10% and 68% for spouses, 36% and 26% for siblings and 29% and 55% for parents. For children of index parents the proportions positive for HBsAg and those negative for HBsAg but positive for anti-HBs and/or anti-HBc were similar whether the index patient was the mother (24% and 24%) or the father (26% and 18%). Our results suggest that horizontal transmission is a significant mode of spread of hepatitis B within the family in Singapore.

Characterization of HBV2-like infections in Spain

Hepatitis B viral serum markers suggestive of infection by hepatitis B virus type 2 were found in 354 patients tested in the laboratory during a 2.5 year period of study. Confirmation of the HBsAg reactivity by neutralization and subtyping analysis and determination of serum HBV-DNA by molecular hybridization were carried out on selected samples from these patients. Clinical and epidemiological data were obtained from 234 patients and serological follow-up was done in 70 cases. The results obtained from the confirmatory tests and DNA assays indicated that HBsAg reactivities were specific, being frequently associated to low levels of HBV-DNA. The incidence rates obtained for HBV2 serological patterns among patients at different level of risk for HBV infection, as well as the finding of a high rate of coinfection with hepatitis A virus among those showing acute hepatitis, suggested that the HBV2 agent could be transmitted by the oral route. An hypothesis considering the so called HBV2 infections as resulting from infections by an HBV variant strain which has an improved ability for non-sexual, non-parenteral transmission is suggested. Specific recommendations for detection and confirmation of such cases in blood banks are also outlined.

Hepatitis B infection of children in a mixed-race community in western New South Wales

A seroprevalence survey of markers of hepatitis B virus (HBV) infection in children aged 0-16 years was conducted in a mixed-race township in western New South Wales. A total of 408 children were screened representing 95% of the total 0-16-year-old population. Of the Aboriginal subjects, 69% had seromarkers which indicated previous infection with HBV and 14% were hepatitis B surface antigen (HBsAg) seropositive. In the non-Aboriginal subjects the prevalence of seromarkers was 10% with no subjects HBsAg positive. The township provided an ideal setting for studying possible crossinfection from children in a high risk (Aboriginal) population group to children in a low-risk (non-Aboriginal) group. The ratio of children in the high-risk group for HBV infection to those in the low-risk group was approximately 2.7:1. Although HBsAg was highly endemic in the Aboriginal population, the data indicate that little crossinfection has occurred. We conclude that in this and similar mixed-race communities action should be taken to accelerate vaccination programmes aimed at reducing HBV infection among neonates and children in the high-risk groups. This will provide an immediate overall reduction of potential risk to both high-risk and low-risk groups while the issue of universal vaccination is considered further.

Horizontal transmission of hepatitis B virus amongst British 2nd World War soldiers in South-East Asia

Infection with hepatitis B virus (HBV) is much more common in tropical than in temperate countries. Visitors to the tropics are thus at risk from HBV, though the degree of risk, and the routes of infection involved are uncertain. We report serological markers of HBV in two groups of 2nd World War soldiers, who served in the Thai/Burma jungles. The groups comprised 100 ex-prisoners of the Japanese (POW), and 100 Burma Campaign Veterans (BCV). Surface antigen to HBV (HbsAg) was positive in 0% of POW and 2% of BCV (P = not significant). Surface antibody (anti-HBs) and core antibody (anti-HBc) were both positive in 40% POW and 13% BCV (P less than 0.001). Quoted UK prevalence rates for these markers are 0.1% for HBsAg, 1.5% for anti-HBs and 0.7% for anti-HBc. Both groups thus show very high rates of past HBV infection. For the POW there were many possible reasons, including contaminated surgical instruments and needles, blood transfusions, and multiple beatings with common weapons. None of these factors operated significantly for BCV. Malarial transmission was, however, intense in both groups, though more so in POW. The data thus again raise the possibility of horizontal transmission of HBV by biting insects in tropical countries.

The hepatitis B virus

Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.

Markers of hepatitis B virus infection in schoolchildren in the Kimberley, Western Australia

In 1986 the Aboriginal community in Western Australia was identified as a high-risk group for hepatitis B virus infection. An immunization programme was commenced in 1988 but concerns were expressed about horizontal transmission, especially in schools, to the low-risk Caucasian group and whether they should also be included in the vaccination programme. To estimate the extent of this occurrence, a survey of schoolchildren from two district high schools in Broome and Derby in the Kimberley Region of Western Australia was carried out in March 1989. A total of 607 students aged 4 to 19 years were included in the study. None of the 300 Caucasian students had any serological markers of hepatitis B virus infection (95% confidence interval (CI) upper limit, 1.3%). Eighteen children were found to be seropositive for hepatitis B surface antigen (HBsAg); 17 were Aboriginal and one Asian. In addition, 61 Aboriginal students and one Asian had hepatitis B surface antibody (antiHBs). The hepatitis B virus infection rate in these Aboriginal children is 28.2% (95% CI, 23.2%-33.7%) with a carrier rate of 6.1% (95% CI, 3.9%-9.6%). This study demonstrates that Caucasian students have a very low risk of infection with hepatitis B virus in this community, and there is therefore no need to extend the hepatitis B vaccination programme beyond the already identified high-risk groups.

Vaccination of infants and children against hepatitis B

Hepatitis B infection and its sequelae constitute a significant public health problem in the United States. It is estimated that 300,000 acute hepatitis B infections occur each year, with about 25% accompanied by both clinical illness and jaundice. Some infections become chronic and ultimately may cause development of liver cirrhosis or primary hepatocellular carcinoma. The risk of chronicity is especially great with infections that occur in infancy. Highly effective vaccines comprised of purified hepatitis B surface antigen (HBsAg) particles are now available for the prevention of hepatitis B infection. A first-generation vaccine utilized HBsAg derived from the plasma of infected persons; this has now been replaced by two similar vaccines that incorporate HBsAg produced by genetically engineered strains of the common bakers' yeast, Saccharomyces cerevisiae. Improved use of vaccine is needed to reduce and ultimately eliminate hepatitis B infection. Vaccination already is recommended for persons recognized to be at increased risk of exposure to virus-containing blood or other body fluids (e.g., infants born to carrier mothers, household or sexual contacts of carriers); however, mass vaccination of adolescents and infants is needed to interdict effectively a majority of all exposures to the hepatitis B virus.