Prevalence of hepatitis B surface antigen (HBsAg) positivity and its associated factors in Rwanda

Viral hepatitis caused an estimated 1.34 million deaths in 2015 worldwide [1]. These deaths were as many as those caused by tuberculosis and higher than those caused by HIV [2]. Most (720,000) hepatitis related deaths were due to liver cirrhosis, followed by primary liver cancer i.e. hepatocellular carcinoma (470,000 deaths) [3]. Globally, an estimated 257 million people were living with chronic hepatitis B infection (HBV) in 2015, and the global prevalence of HBV infection in the general population was 3.5% [4]. However, the prevalence of chronic HBV infection is much higher among people born before the HBV vaccine became available [5].

Despite the introduction of universal HBV vaccination and effective antiviral therapy, the estimated overall seroprevalence of HBV surface antigen remains high in Africa at 6.1% [6] and the Western Pacific regions (6.2%) [1]. According to the World Health Organization (WHO), HBV infection affects more than 5% of the local population in sub-Saharan Africa, with more than 8% in West Africa and reaching up to 15% in some areas [7]. In East African countries, only a few studies have been conducted on the epidemiology of viral hepatitis, and most of these studies focused on specific subpopulations, e.g. those living with HIV [8‐13]. Data for the general populations are mostly unavailable.

In Rwanda, HBV prevalence data is only available among specific population subgroups. One study among 13,121 pregnant women in 30 sentinel sites found a prevalence of HBsAg of 3.7% [8]. A recent study of 117,258 people living with HIV (PLHIV) found a prevalence of HBsAg of 4.3% [10]. However, there are limited data on the epidemiology of HBV in the general population.

In order to better understand the seroprevalence of HBV in the general population of the country, the Rwanda Biomedical Center (RBC) and its partners conducted several HBV screening campaigns to inform HBV prevention and treatment programming in Rwanda. This article analyzed the prevalence and risk factors of HBsAg seropositivity among people who participated in a national hepatitis screening campaign in Rwanda.

This study was the first national-level study of HBsAg prevalence in Rwanda and showed that the overall prevalence of HBsAg positivity was 3.9% in the screened population. This prevalence is comparable to the 4.3% prevalence among PLHIV and the 3.7% prevalence among pregnant women in Rwanda [8, 10]. From 2015 in Rwanda, there have been several wide scale vaccination campaigns among people at risk for HBV; these campaigns may have lowered the prevalence in adults. These findings indicate that the Rwandan HBV prevalence is intermediate according to WHO criteria, as the prevalence ranges between 2 and 8% [16]. Nearby East African countries also have prevalence ranges estimated at 2–8%. For example, Kenya, Tanzania, and Ethiopia have general population prevalence reported at 2, 6, and 8%, respectively [4, 13, 17].

In addition to estimating the prevalence of HBV infection in the population screened, this study has identified different factors associated with prevalent HBV infection. Identification of risk factors is essential as it informs HBV prevention programming especially in resource-limited countries [18]. The factors associated with HBsAg positivity in this study included male sex, province of origin, and some clinical and behavioral characteristics including history of tuberculosis, exposure to blood transfusion, and viral hepatitis in the family. These factors have also been identified to be associated with HBV infection in other studies. Many of the identified factors have very low odds ratios (and may have been overpowered given the large sample size).

Male sex was one of demographic characteristics associated with HBsAg positivity in this study. The reasons behind this association may be that males may be more prone to high risk behaviors like sexual contact, violence and conflicts in which blood contact may occur. Other studies from Pakistan [19] and Tanzania [13] also found that male sex was associated with HBV infection. In Rwanda, a prior study conducted among PLHIV also found higher HBV infection among men [10].

High HBsAg prevalence was found in Eastern province with the peak prevalence in Kirehe district (8.4%) as presented in Fig. 2. The Eastern province of Rwanda has a large number refugees and other migrants from bordering countries. It is possible that this population has a higher risk of HBV acquisition due to unhygienic living conditions, low vaccination rates, or possibly behaviors (like traditional scarification). The Eastern Province has now been targeted for future HBV vaccination campaigns.

Among risks factors found in this study, certain clinical characteristics like a history of tuberculosis, surgical operation, and traditional operational practices and scarification and a history of viral hepatitis in the family were found to be associated with HBsAg positivity. Being exposed to blood and blood products through medical and non-medical practices is the main source of HBV transmission and could be the reason why these factors were associated with HBV infection in this study. Previous studies have identified exposure to blood products, history of surgical operations, history of HBV in the family, undergoing body piercing as risks factors for HBV [20‐25]. In a study conducted in Sao Paulo, Brazil HBV infection was associated with a family history of hepatitis and tattoos practicing [26] were reported as main factors associated with HBV. Over the last decade, Rwanda has made great strides in securing and testing the blood supply, and it is though that iatrogenic HBV exposures should continue to decline.

The results from this study provide an estimate of the prevalence of HBV infection in Rwanda based on a large number of diverse participants from different districts in the country. These estimates help to inform HBV prevention and treatment programming in Rwanda while waiting for more generalizable prevalence estimates from studies conducted on random national samples. Additionally, identification of factors associated with HBV in this population can allow the design and implementation of interventions targeted to the most at risk populations in Rwanda. For instance, organizers of HBV screening, prevention and treatment programs could prioritize groups that were identified to be most at-risk including people with a history of TB, transfusions, and those from families with a history of HBV infection.

This study has strengths and several limitations. The study strength is its very large sample size and high coverage of 24 of the 30 districts in Rwanda (80%). However, the study population was not randomly selected and did not include Kigali city, so the prevalence results may not be generalizable to the whole country. There is also a possibility of selection bias, as people who participated in the screening program may have been more likely to have current symptoms, already know their HBV status, or be more likely to be HBV-infected. This study was aimed at individuals aged 25 years and older; the prevalence of HBV is likely higher in this group than in those under 25 years in Rwanda, as childhood HBV vaccination programs were begun in 2002. Future studies will need to determine the prevalence among the population less than 25 years old. Another bias may have been introduced by encouraging older individuals to come for testing, which may have resulted in an unequal age distribution. This study relied on chart review and self-reported information for clinical variables (e.g. HIV status) which may have led to misclassification through recall bias. There were also a limited number of variables available for analysis in the chart (e.g. HBV vaccination status), limiting the number of factors and confounders that could be included in the analysis. Finally, this study relied on HBsAg testing to determine prevalence of active HBV infection. Therefore, participants with acute infection or other chronic carriers may have been missed, thus underestimating the total burden of HBV disease. Without liver function testing or fibrosis data, subjects could not be assessed for the impact of chronic HBV infection. Despite these limitations, this study provides valuable baseline prevalence estimates to inform HBV programming in Rwanda and identifies groups for focused prevention efforts. Future studies using random sampling techniques may give a more complete estimation of the national prevalence.

This study shows that HBV is an intermediate epidemic in the studied population in Rwanda. The findings are similar to little available data on HBV in the region and may be applicable in other similar settings. These results have also identified groups of people with the highest HBV risk in Rwanda. More studies are needed in order to have people that should be prioritized in prevention interventions.