Hepatitis B virus (HBV) infection is a serious global public health problem. It is estimated that there are around 400 million chronic carriers of the hepatitis B virus (HBV)  and more than one million deaths per year worldwide (WHO, 2016; Atipo-Ibara et al., 2015). Estimates of hepatitis B antiginaemia    seroprevalence   of   5-20%    have   been reported (Te and Jensen, 2010), making sub-Saharan Africa a hyper-endemic region. The lifetime and mortality risks from hepatitis B infection in this region are estimated to be around 25% (Matthews et al., 2014). In countries in sub-Saharan Africa, hepatitis B virus seroprevalence levels ranging from 8 to 15% have been reported in blood donors (Tagny et al., 2010).

Gabon, a middle-income country of approximately 2 million inhabitants, with approximately 241,080 individuals with hepatitis B (Makuwa et al., 2009; Bivigou-Mboumba et al., 2016; Schweitzer et al., 2015), is among the countries of 'High endemicity with marked heterogeneity of HBsAg seropositivity among population subgroups.

In Gabon, some studies have reported the prevalence of HBsAg in first time blood donors, with estimated rates ranging from 5.63 to 7.28% (Kounegnigan Rerambiah et al., 2014; Eko Mba et al., 2018). However, there is little literature on assessment of the prevalence of HBsAg among blood donors in the Estuary region, Libreville in Gabon.

Determinants and markers of hepatitis B virus disease outcome pose challenges in understanding the routes of transmission of infection and characterizing actively infected individuals. While transfusion of infected blood and unsterile needles played a role (Jayaraman et al., 2010; Eke et al., 2015), host factors (exposure to alcohol, traditional medicine, sex, age, presence of co-infections) and environmental factors do not support transmission via a singular mode (Ragheb et al., 2012; Hoffmann et al., 2012). An earlier study in Gabon suggested that certain demographic and behavioural factors were potentially relevant modes of HBV transmission (Groc et al., 2019). These data mainly concern the general population with low socio-economic status and high risk groups. However, blood donors including those mono-infected with HBV were not taken into account. We thus sought to assess the seroprevalence and risk factors associated with HBV infection among blood donors in Gabon.

Ethics statement

The study protocol was reviewed and approved by the National Ethics Committee for Research (Authorization n° 0088/2019/PR/SG/CNER) and the National Blood Transfusion Center (Authorization n° 527 /MS/SG/CNTS/DG) of the city of Libreville, Gabon. After obtaining verbal informed consent, their answers to 12 questions were recorded.

Study design, setting and population

This cross-sectional and analytic study was carried out on data from blood donors recorded by the blood bank in the Gabon Estuary area, from June 2020 to August 2020 (Figure 1). The Gabonese National Blood Transfusion Center is the largest specialized institution for the collection and supply of blood in the Gabon Estuary. Currently, the amount of blood collected by the Blood Center is approximately 22, 200 units each year. There are two collection methods in this transfusion center, in particular a collection on a fixed site and on a mobile site from which a mobile vehicle ensures the collection.

From June to August 2020, a total of 3665 donations were collected on fixed site. Out of 3665 blood donors, 1610 (43.9%) were first-time blood donors that were screened at the Gabonese National Blood Transfusion Center. The age distribution of blood donors is shown in Table 1. The proportions of male and female donors were 65 and 35% respectively. The majority (32.9%) of donors were between 20 and 29 years old, while the younger group (<20 years) comprised the smallest blood donor population (3.6%).

Prevalence of HBV among first time blood donors

In Gabon, the overall  prevalence  of  hepatitis  B  surface antigen among the total number of first-time donations in Gabonese National Blood Transfusion Center during this study period was 5.5% (95% confidence interval [CI] = 4.4 - 6.7) or 88 reactive ELISA tests out of 1610 first time blood donors (Table 3). The highest prevalence was recorded among the 20-29 years age group (8.1%) (95% confidence interval [CI] = 5.9-10.8), higher than that of 30 years and over age group, and the least prevalence of 0% was observed among younger groups (<20 years) donors. Seventy-five (7.2%) (95% confidence interval [CI] = 5.7-8.9) males were tested HBsAg positive as compared to thirteen (2.3%) (95% confidence interval [CI] = 1.2-3, 9) females. The prevalence was highest among males in all the age groups (Table 2) with the risk of being HBsAg positive found to be 3-fold higher in males than in females (Table 3).

Risk factors of HBV infection

From 100 blood donors who tested repeatedly reactive for HBsAg between June and August 2020, 29 declined to participate in the study and 71 (71% of all HBsAg positives) consented to participate in the study. A total of 212 comparison donors of unknown HBsAg status were recruited during the same time period from among 284 randomly selected donors at blood drives approached at the same locations from which the HBsAg positives were drawn. The case-cohort study included 71 cases and 212 comparison subjects. Demographic characteristics are presented in Table 4.

90.4% of the participants were replacement donors, 72.4% resided in Libreville and 43.1% were between 20 and 29 years old against 47.3% for all donors. There were differences according  to  HBsAg  status (Case  and control group) on several socio-demographic and blood donation characteristics, including age, place of residence, voluntary donor versus replacement donors and first-time donor status versus repeat donors. Data on behavioral risk factors according to HBsAg status, with unadjusted ORs, showed that HBsAg positive cases had significantly higher uncorrected odds of having contact with blood exposure (OR= 2.98) (Table 5).

This study documented a prevalence of 5.5% of HBsAg-positive among overall blood donor tested by two rounds of screening with different enzyme-linked immunosorbent assays in post-donation, between June and August 2020.

This was higher than in Marocco in previous studies (1.34%) (Adouani et al., 2013) and in other developing countries such as Burundi (2.5%), Egypt (1.4%), Rwanda (4.1%), Burundi (2.5%), Iran (0.15%) and Botswana (1.02%) (Tagny et al., 2010; Wasfi and Sadek, 2011; Twagirumugabe et al., 2017; Farshadpour et al., 2016; Choga et al., 2019) and some blood bank from industrialized countries like China (0.87%); France (0.65%) and the United States (0.76%) (Song et al., 2014; Meffre et al., 2010; Dodd et al., 2016).

The high rate among blood donors, which represents a large part of the population, objectively reflects the prevalence of HBV in Sub-Saharan Africa (Te and Jensen, 2010). More attention should be paid to blood safety  to  promote  the  need   for  strict  donor  selection criteria.

Several plausible demographic and behavioural risk factors were found to be associated with HBsAg status among blood donors in Gabon. First-time donor status is previously recognised as risk factors for HBV infection. In addition, association with place of residence is a novel ?nding for Gabon and may have relevance for blood safety and public health.

It was amazing to ?nd that donors living outside Libreville had more than 1 time the odds of being HBsAg⁺ than donors from Libreville while adjusting for other factors. The researchers are also aware of recognised high-prevalence areas for HBV in the Libreville region, although a higher frequency of percutaneous exposure could be more common in rural areas. Further investigation of Geography-speci?c lifestyle issues is needed to understand what might explain this increased risk for HBV.

Although not signi?cant in the logistic regression model, having contact with blood exposure were signi?cant in the univariate analysis. This parenteral risk factors is biologically plausible and have been found to be associated with HBsAg status in previous studies (Jayaraman  et  al.,  2010;  Eke  et  al.,  2015).  It  is  also  conceivable that previous reports may have been due to confounding, as we did not detect an association between these variables and HBV after controlling for likely confounders such as age and gender by exclusion and multivariate analysis. Donor deferral based on risk behaviour assessment is a routine part of blood donor screening in the Europe and United States; yet in Gabon, donor screening procedures are not uniform across blood centers. Few centers in Gabon use individual risk behaviour questionnaires.

Local blood bank personnel realise the need for an individual donor screening questionnaire. However, behavioural risk factors for HBV infection and other TTIs in blood donors in Gabon are not well studied.

Volunteer blood donors, especially young volunteer donors representative of demographics currently being recruited to replace family replacement donors in Gabon, are a healthy group of people from low-risk populations (WHO, 2008). They were screened for potential risk factors such as gay men, drug use, and a history of diabetes. These high-risk behaviors were not associated with HBV infection in this study because subjects were excluded from donation. However, this does not mean that these risk factors are not potential factors for infection with HBV. Some blood donors may conceal exposure to high risk factors on the medical history questionnaire. For a complete and accurate investigation, further study is warranted.

Our study had some limitations. Of note, the analysis with HBsAg does not cover occult hepatitis B infection, suggesting an underestimate of the real burden. The sample size was limited and the completeness of the self-reported risk factor questionnaire was not always effective. The study period was semingly short, which restricted time-dependent variation analysis.

Our findings suggest that the prevalence of overt HBV infection is at a moderate-level endemicity among blood donors. Overall, first time blood donation and living in peripheral areas are driven factors of HBV serpositivity. These provide useful information in the development of individual pre-donation questionnaires to defer those at risk from donating blood. However, our study also highlights the need to continue throrough epidemiological surveillance for blood safety in Gabon.

The authors have not declared any conflict of interests.

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