HBV infection is a very large burden in all sub-Saharan African regions3. The present study revealed a significantly high active HBV infection of 10% (95% CI: 9.4 − 10.6%) in the adult population of Luanda, the capital city of Angola. We show that in the last 5 years (2018–2022), the active HBV infection was high (> 8%), ranging from 9.2 to 10.7%. It is worth mentioning that regions with high HBV endemicity have been associated with high mortality rates from primary liver cancer, since chronic HBV infection is responsible for 40% of the global burden of hepatocellular carcinoma (HCC), with a high fatality rate11. Indeed, our research team recently identified that approximately 80% of HBsAg-positive individuals in Luanda, Angola, had chronic liver disease, while 20% had acute liver disease, based on the AST/ALT ratio, indicating that individuals up to 40 years old (OR: 1.97), women (OR: 1.61), living in non-urbanized areas (OR: 1.69), with low educational level (OR: 1.64), and unemployed (OR: 1.81) were more likely to develop chronic liver disease12. These findings showed that authorities should consider including nucleic acid testing (NAT) to ensure the identification of occult infections, as well as provide an assessment of liver function in HBV-infected individuals, whether in the acute or chronic phase.
In the present study, active HBV infection is associated with certain sociodemographic and behavioural determinants such as age, gender, occupation, residence and marital status, that elucidate the multifaceted impact of sociodemographic and behavioural determinants on HBV infection risk, underscoring the necessity for targeted public health interventions in Angola. Indeed, the multivariate logistic regression model applied in the studied population revealed that men, employees and non-urbanized areas are more likely to test positive for HBsAg, while adult individuals aged 30 or over, and married were less likely compared to their counterparts.
The trend of active HBV infection over time in the capital of Angola increased from 16.8% in 2018 to 21.9%, equivalent to a rise of 5.1%. These results could jeopardize the WHO’s goal of eliminating viral hepatitis as a public health problem by 2030 1. The interactions between different sociodemographic and behavioural characteristics with susceptibility to HBV infections over the years remain poorly understood in Angola. According to our findings, the increase in active HBV infection in the Angolan population has been driven by the youngest individuals aged up to 30 years old, male, employed/student, resident in urbanised areas, and unmarried.
Younger individuals under 30 years old had a prevalence ratio of 1.52 times more likely to acquire HBV infection, with a prevalence of around 10.4 − 12.4%, which may be attributed to potential gaps in vaccination coverage or behavioural factors. As reported in other studies, in the age group up to 30 years, the most prominent presumptive source of HBV infection is sexual because it is a sexually active age13. However, future studies investigating the proportion of presumptive sources of HBV infection according to age should be carried out in Angola. Previous studies have indicated that prevalence rates in younger individuals in sub-Saharan African countries are up to 12% and are more pronounced among men3, which is consistent with our results, where a prevalence of 11.4% (95% CI: 10.4–12.4%) was observed in the young population aged 18–29 years, and the male gender is also predominant. From 1990 to 2005, there was an overall decrease in HBsAg prevalence in younger age groups globally, which might be closely related to widespread immunisation against HBV14. However, the increase in seroprevalence in the youngest Angolan population from 31.3% in 2018 to 52.5% in 2022 suggests a failure of immunisation measures against HBV in the younger population requesting urgent public health intervention in this risk group.
We revealed a remarkably increasing HBV positivity rate between 2018 and 2022 among males, although no statistical significance was observed (p = 0.149). Studies conducted with blood donors in Malaysia15, Brazil16, and China17 have also shown that male was associated with HBsAg seropositivity. Other studies conducted in Angola have also shown an increase in the prevalence and risk of sexually transmitted infections (STIs) such as HIV, HCV and Syphilis in the male population living in the capital of Angola7,18,19, pointing to men as the main source of the spread STIs. It is worth mentioning that unhygienic tattoos, piercings, high-risk sexual activities, and alcohol consumption are common practices among young men aged up to 30 years in Luanda. Therefore, conducting studies on the association between lifestyle or occupational risks and HBV could ensure control of the spread of HBV and related diseases in Angola.
The profile of infected individuals differed significantly according to place of residence, with non-urbanized areas being the most affected, with 10.1% prevalence and a prevalence ratio of 1.19 times (95% CI: 1.06–1.33, p = 0.004) more likely to be infected. Other studies have also reported that those living in non-urbanized areas had a higher risk of being HBsAg positive15. Differences in access to information about health services and prevention information, lifestyle, educational level, income, and other socioeconomic status of the population living in non-urbanized areas could help explain the increased prevalence as well as the high risk of HBV in these regions. Therefore, these findings emphasized that national strategies to prevent HBV infection should consider regional differences and demographic/socioeconomic status.
Interestingly, individuals with employment or some monthly income were 2.8 times more likely to contract HBV infection, suggesting that individuals with monthly income or financial power tend to have more than one sexual partner and engage in risky sexual practices which promote the dissemination of infectious agents. The number of sexual partners and its relationship with viral hepatitis was not assessed in the present study and deserves further investigation. Contrary results were observed in a study conducted with blood donors from Somalia, which found that unemployed blood donors (AOR = 3.78, 95% CI: 1.17–12.2), were more likely to become infected with HBV20. On the other hand, and as expected, married individuals were 0.62 times less likely to acquire HBV infections. These results may reflect the involvement of unmarried individuals with casual sexual partners and low use of protective measures during sexual encounters. Different results were observed in studies conducted in Pakistan, which showed that being married was significantly associated with HBV infection21, which can be explained by the shared use of common materials or equipment by the couple during family life, such as sharing personal hygiene items.
Some limitations should be considered in our study. The population of blood donor candidates may not represent the general population of Luanda, as well as the entire population of Angola. Our questionnaire included limited sociodemographic data to investigate risk factors for active HBV infection. We did not include important demographic determinants known to play a crucial role in the spread of viral hepatitis, such as sharing personal hygiene items, medical procedure history, practices associated with drug use, and sexual risk behaviours. Therefore, it is recommended that further studies be conducted to obtain more estimates of HBV infection considering questions that will examine a broader set of determinants related to STIs. Previous studies have also documented that HBV genotype might influence local epidemiology, due to variations in spatial distributions and genotype-specific determinants that affect its transmission potential. Therefore, further studies should investigate HBV genotypes as well as their impact on the increase in active HBV infection cases in Angola. It is also worth mentioning that the HBsAg used in the present study does not detect past infections and/or antibodies resulting from vaccination, suggesting that studies using other markers such as HBcAb (to identify exposure) and HBsAb (to detect immunity) should be performed including individuals HBsAg negative so that we can get a better picture of the HBV seroprevalence in Angola. Despite the weaknesses, our results highlight the growth of active HBV infections in the young Angolan population, which could serve to better understand the socioeconomic impact of STIs, evaluate the success of the HBV vaccination program and ensure targeted intervention in vulnerable populations to prevent new infections in Angola.
