To determine the effect of age on the prevalence of hepatitis B virus (HBV) infection during a routine screening programme of first-year students enrolled in Health Sciences Studies at the Chinese University of Hong Kong from 2001 to 2009.

In a retrospective cohort study, data on the hepatitis B surface antigen (HBsAg) status was retrieved from the University Health Service and analysed according to the age of the student at testing and year of birth.

Of the 2,688 students enrolled in the study group, 79 (2.9 %) tested positive for HBsAg. The prevalence increased significantly from 0.9, 2.3, 4.3 to 5.5 % for those tested at age ≤ 18, 19, 20 and ≥ 21 years, respectively (p < 0.001). On logistic regression analysis, taking age ≤ 18 years and year of birth before 1983 (before the availability of HBV vaccination) as the reference group, HBV infection increased progressively with age, with an adjusted odds ratio of 3.36 [95 % confidence interval (CI) 1.01-11.23], 6.04 (95 % CI 1.74-20.98) and 11.61 (95 % CI 3.20-42.13) for age 19, 20 and ≥ 21 years, respectively. There was no significant change in the odds ratio after adjustment for the year of birth before and after introduction of the vaccination programme.

Among the university students enrolled in our study, the overall prevalence of HBV infection before and after the introduction of HBV vaccination was lower than the 10 % found in the general population. There was, however, a significant progressive increase with age at testing from ≤ 18 to ≥ 21 years, suggesting a previously overlooked contribution of horizontal transmission to the high prevalence of HBV infection found in our adult population.

Familial clustering of HBV provides epidemiological evidence for the different modes of spread of the virus. Though the majority of the studies have addressed the issue of perinatal transmission in India, only a few reports have dealt with other modes of transmission.

The study was prospectively designed and data were collected from a total of 265 household contacts of 91 index patients with HBV-related chronic liver disease between January 2006 and July 2007. The prevalences of HBsAg and various antibodies; anti-HBs, anti-HBc and anti-HBe, were estimated in all household contacts using ELISA and VIDAS.

Among the various household contacts, the highest prevalence of HBsAg was seen in the pediatric age group (kids 1-15 years: 37.0%) and especially in siblings (48.3%), with statistical significance (p < 0.001). Hepatitis B virus (HBV) serological markers were found more commonly in contacts of female (68.8%) index patients as compared to males (p > 0.05). The development of anti-HBV antibodies showed an increasing trend with age (p < 0.001), with the highest prevalence in parents.

Horizontal transmission plays an important role in contributing to the high prevalence of HBsAg especially in young children. Hence, this age group needs to be targeted for primary prevention and effective vaccine.

Hepatitis B virus (HBV) infection is a worldwide health problem. The aim of the present study was not only to determine the prevalence of HBsAg in children of HBV-infected parents but also to identify all HBSAg-positive family members to protect as many children, in the present and future, as possible. The study was carried out with the participation of 2113 family members (1205 children, 453 mothers, and 455 fathers) at Sivas SSK Hospital, Turkey. They were screened for HBV markers using standard enzyme immunoassay between September 2001 and March 2005. The prevalence of any HBV markers and HBsAg among family members of index cases was 50.5% and 30.5% respectively. HBsAg carrier rate was higher among fathers (61%) than mothers (47%), (P<0.05). The children of mother index cases had higher rates of HBsAg compared with the children of father index cases (P<0.01). Our results suggest that intra-familial childhood horizontal transmission (especially mother-to-child) is important for HBV transmission in the Turkish community, and highlights the need for screening of adult siblings and mothers of adult HBsAg carriers in addition to their spouses and children.

Hepatitis B is endemic in the Amazon region.

Serological markers for hepatitis B virus (HBV) were determined in 266 household members for hepatitis B surface antigen (HBsAg)-positive women (G1) and 395 household members for HBsAg-negative women (G2), randomly selected in Acre State Women's Medical Care Program, in order to evaluate the prevalence of HBV in this population. Before blood sample collection an epidemiological questionnaire was applied.

The overall prevalence of HBV carriers (HBsAg) and exposed individuals (anti-HBc, IgG) was, respectively, 21.1% and 60.5% in G1 and 2.8% and 27.4% in G2 (P < 0.0000001). The frequency of HBsAg was higher among siblings from group G1 (75%) compared to the absence of any HBsAg-positive sibling in G2 (P < 0.00006). The HBV markers in other family members was as follows: G1 parents, 27.3% vs 4.5% (P < 0.03), sexual partners, 21.1% vs 2.5% (P < 0.04), and offspring, 10.4% vs 1.5% (P < 0.04). A low prevalence of HBsAg and anti-HBc (IgG) was observed for the last offspring of G2 mothers compared to the high prevalence among children of G1 mothers (0% vs 18.2%, P < 0.01 and 2.3% vs 59.1%, P < 0.0000005, respectively), with children younger than 1 year being the most affected. The frequency of the habit of sharing toothbrushes and the presence of at least one HBsAg carrier were higher in G1 than in G2 (P < 0.0001 and P < 0.000002), respectively. Genotypes A, D and G were found to be predominant by Innolipa test. There were cases that reacted to more than one genotype.

Intrafamilial transmission of HBV is evident in the present study and is possibly associated with the presence of more than one HBV carrier in the family and the shared use of toothbrushes among household contacts. Genotype analysis confirms intrafamilial transmission.

Quantitative determination of hepatitis B virus (HBV) DNA concentration is the most important measure for an estimation of the infectivity of an HBV positive health care worker and the basis for the decision whether he or she is allowed to perform exposure prone procedures. Thus questions are raised on how reliable quantitative HBV DNA assays are, and how stable is the HBV DNA concentration is in a healthy chronic HBV carrier. Therefore, in the present study two commercially available quantitative HBV DNA assays, the Amplicor HBV Monitor and the HBV Test Hybrid Capture II, and an "in house" quantitative HBV TaqMan PCR, analysing 101 sera of HBsAg positive patients for HBV DNA were compared. In addition, HBV DNA concentrations were followed in 14 healthy chronic carriers for up to 6 years. Despite a good overall correlation between the three tests considerable differences were found for the results of individual sera. Fifty-one percent of sera showed differences within one order of magnitude, 45% differed by a factor above 10 and 4% even by a factor of 100 and higher. The follow-up of the HBV DNA concentrations in 14 carriers showed in 7 carriers a rather stable course with variations within one order of magnitude, whereas in the other half the DNA concentrations fluctuated by factors between 10(2) and 10(6) over the observation period. Thus, viral load determinations in health care workers have to be interpreted with some caution, especially when they are the basis of far-reaching decisions.

Three-hundred forty-one HBsAg-positive family members of 152 patients with chronic hepatitis B virus infection (47 asymptomatic carriers, 59 with chronic hepatitis, 17 with cirrhosis and 29 with hepatocellular carcinoma) were prospectively studied to determine the morbidity and mortality from chronic hepatitis B virus infection in the family members of patients with malignant and nonmalignant hepatitis B virus-related chronic liver diseases. Most of the family members had no history of acute hepatitis, were asymptomatic and were unaware of their carrier status. However, 5.3% had stigmata of chronic liver disease, 6% had serum ALT levels that exceeded two times the upper limit of normal and 78% of those who had biopsies had chronic hepatitis with or without cirrhosis. During a follow-up period of 12 to 90 mo (median = 39 mo), 3% had symptoms of chronic liver disease; 24% had transient, recurrent or persistent elevation in serum ALT levels, 1.4% had cirrhosis and 1% had hepatocellular carcinoma. Neither hepatocellular carcinoma in the index patient nor a previous history of hepatocellular carcinoma in the family was associated with an increase in the morbidity and mortality from chronic hepatitis B virus infection in the HBsAg-positive family members.

A sero-epidemiological survey was carried out in Cameroon in January 1989 on a sample of 702 children of primary school age. A high HBV endemicity level was observed: 60.3% of the sera were positive to any HBV marker, 23.2% (163 sera) were HBsAg-positive. HBV-DNA positivity was observed in 38/163 (23.3%), thus showing a high level of infectivity among these carriers. Seventy-seven HBsAg-positive sera were tested for HBeAg/anti-HBe: 20 (26%) were HBeAg-positive 31 (40%) anti-HBe-positive, and 26 (34%) were negative for both. All sera were anti-HD-negative. Twenty-five per cent of HBeAg-positive sera were HBV-DNA-negative. This finding could be explained by a delayed HBeAg/anti-HBe seroconversion phase with fluctuant HBV-DNA. Only one case of HBV-DNA-positive anti-HBe-positive serum was observed. This study showed that HBV-DNA prevalence was significantly higher in boys (31.8%) than in girls (14.1%) (p less than 0.02). This difference was not observed for any HBV marker. We therefore conclude that in boys a prolonged HBV replicative phase might explain the observed high chronicity rate.