The Japanese oversea immigrants have a history exceeding more than 100 years. Today, there is an estimate of 2.5 million Japanese-descendent people living outside Japan, of whom 1.3 million are in Brazil and one million in the United States .
Overall, the US population has approximately 0.2% of HBsAg positive individuals, but figures are different within ethnic groups. African Americans presented higher prevalence than Caucasians and Asian Americans even higher, especially the immigrants from China and Southeast Asia . In Brazil, data on prevalence of hepatitis B among Asian descendents as a comparative study between different ethnic groups are scarce and not precise.
In the present study, Asian relatives from patients with chronic hepatitis B (CHB) have shown higher anti-HBc and HBsAg prevalence than that observed in family members of patients from Western origin (Table 3). These results are very similar to the presented by others and to the predicted and observed prevalence from the mathematical model developed by Carrilho in 1987 [11–14].
At the "Hospital das Clínicas", research on familial HBV carriers began in 1971, when Carrilho and collaborators studied 19 Asian and 26 Western CHB patients and 165 and 186 respective relatives . The latter study found that, altogether, the prevalence of HBsAg and anti-HBs was 135/165 (81.8%) in the Japanese and 68/186 (36.5%) in the occidental relatives (p < 0.0001). These data are similar with those of the present study which, in turn, may also be confirmed by the mathematical model described by Carrilho .
It is noticeable in the present surveillance that 110 cases of HBsAg-positive individuals – the majority of Asian origin (Table 3) – were identified, whom otherwise would not have been diagnosed. Further study comparing the natural course of chronic hepatitis B in these populations is needed to assess the benefit of early detection of the disease.
The findings of a greater prevalence of HBsAg among the Asian families and, for the Western equivalents, a higher prevalence of anti-HBs suggest the longer state as chronic carriers for the Asians (Table 4). This may be due to the age of acquisition of the disease, which may influence the prognosis . Children infected by vertical route (mother to child) may have greater tolerance to HBV with less hepatic damage, but greater prevalence of the chronic stage . In fact, when we analyzed the mode of transmission of HBV in the proband groups (Table 6), it was observed that "mother to child" transmission was greater among the Asian patients and "sexual" transmission among the Western ones. Yet, it is important to mention that notable differences exist in the prevalence of acute flares of hepatitis in Asian and Western patients . Studies in patients with CHB have shown more serological fluctuation in Asians than in patients in the United States . In a study with 224 HBeAg positive Asian patients, flares of disease activity occurred in 40% but, unlike observed for the Western counterparts, this seldom led to seroconversion or to a sustained virologic response , what is in agreement with our results. The differences in the natural history of the infection in Asian and Western patients get particularly relevant when deciding on the need of antiviral treatment.
The marker anti-HBc was more frequent among Asian parents and brothers and the HBsAg, in turn, was more so in Asian mothers, brothers and sons (Table 5). These differences are significant and suggest, specially for the Asian subjects, that vertical or peri-natal transmission from mothers are the most significant way of acquiring HBV infection. The importance of familial screening for hepatitis B among the brothers and sisters of the Asian probands is highly endorsed by the finding of 81% HBsAg positive among their brotherhood.
While anti-HBc is the principal marker for HBV prevalence study in any population, anti-HBs is the hallmark of immunity conferred by vaccination or recovery from HBV infection. In the present study, for economical reasons, anti-HBs was checked only in those who were anti-HBc positive, thus investigating only the recovery cases. Since extended hepatitis B vaccine program was introduced in low prevalence areas in Brazil only in 1998 and vaccine was available for risk groups only, it remains important to evaluate the vaccine coverage in those areas.
In conclusion, Asian relatives from chronic HBV carriers have presented a greater prevalence of HBV markers when compared to Western equivalents. More Asian family members were HBsAg positive while more Western relatives presented anti-HBc and anti-HBs positive. Considering that hepatitis B can be asymptomatic, the present results emphasize the importance of screening the families of the CHB carriers, increasing the chances of a better treatment outcome and helping to halt the spread of this infectious disease.