Epidemiology of hepatitis B virus in Africa, its genotypes and clinical associations of genotypes

Abstract

Of approximately 360 million people in the world chronically infected with hepatitis B virus (HBV), 65 million reside in Africa. Thus, Africa, with 12% of the world's population, carries approximately 18% of the global burden of HBV infection, with hepatocellular carcinoma and cirrhosis accounting for 2% of the continent's annual deaths. Despite HBV being endemic or hyperendemic in Africa, there is a paucity of data on the genotypes and their distribution. Genotype A is found mainly in southern, eastern and central Africa. Most African genotype A strains belong to subgenotype A1, with subgenotype A3 found in western Africa. Genotype D prevails in northern countries and genotype E in western and central Africa. Ithas become increasingly evident that heterogeneity in the global distribution of HBV genotypes may be responsible for differences in the clinical outcomes of HBV infections and the response to antiviral treatment and vaccination. A limited number of studies have been published relating genotypes to clinical outcomes in African countries. Because observations from other regions of the world can not be extrapolated from one locale to another, the HBV strains circulating in Africa should be studied and related to clinical outcomes.

A novel hepatitis B virus (HBV) subgenotype D (D8) strain, resulting from recombination between genotypes D and E, is circulating in Niger along with HBV/E strains

“…HBV/E is the most prevalent genotype in Africa, spreading in a vast crescent, with a span from Senegal to Namibia. In contrast, HBV/A strains are relatively rare, and are found mainly in southern, eastern and central Africa (Hubschen et al, 2009;Kramvis & Kew, 2007;Kramvis et al, 2002;Owiredu et al, 2001), whilst HBV/D is the dominant genotype in northern Africa (Ayed et al, 2007;Bahri et al, 2006;Ezzikouri et al, 2008;Khelifa & Thibault, 2009;Meldal et al, 2009). However, although HBV/E strains are predominant in Africa, they show a low genetic diversity.…”

“…In contrast, several subgenotypes of genotype A (A1-A5) and a potential new subgenotype identified in Rwanda (Hubschen et al, 2009) have been reported in Africa (reviewed by Andernach et al, 2009; see also references herein). Similarly, three of the seven subgenotypes identified so far for HBV/D (D1, D3 and D7) were isolated in Africa -in Egypt, South Africa and Tunisia, respectively (Kramvis & Kew, 2007;Meldal et al, 2009).…”

“…Very recently, new HBV/ D-E recombinants were identified in the Central African Republic, Ireland (in a west African patient), Tunisia and Guinea, with all of them sharing the same recombination profile (Bekondi et al, 2007;Garmiri et al, 2009;Laoi & Crowley, 2008;Meldal et al, 2009). Interestingly, Niger is situated in the Sahara region, between the Maghreb (Algeria, Morocco and Tunisia) in the north, where HBV/D is predominant (Khelifa & Thibault, 2009), and Mali, Burkina Faso, Benin and Nigeria in the west and south, where HBV/E is predominant (Hubschen et al, 2008;Kramvis & Kew, 2007). Two earlier studies showed that Niger is a region highly endemic for HBV infection, with an HBV surface antigen (HBsAg) seroprevalence ranging from 17.6 % (Soubiran et al, 1987) to 29.8 % (Cenac et al, 1995.…”

“…int/csr/disease/hepatitis/HepatitisB_whocdscsrlyo2002_2.pdf), among whom over 360 million are in a chronic carrier state with a high risk of developing cirrhosis and hepatocellular carcinoma (Ganem & Prince, 2004;Lee et al, 1997;Lok, 2004). About 70-140 million of these carriers live in Africa, and about 250 000 of the 1.3 million HBV-related deaths recorded each year throughout the world occur in Africa (Andernach et al, 2009;Hubschen et al, 2008;Kramvis & Kew, 2007;Kramvis et al, 2002;Mulders et al, 2004). HBV belongs to the family Hepadnaviridae and is characterized by a partially double-stranded circular DNA genome of 3These authors contributed equally to this work.…”

Avaliação de fatores virológicos associados ao desenvolvimento de carcinoma hepatocelular (CHC) em pacientes com hepatite B crônica

“…Sabe-se também que os genótipos se correlacionam com as regiões geográficas, motivo pelo qual são boas ferramentas para estudos epidemiológicos (33). Existem genótipos associados a distintas regiões geográficas do mundo, de tal maneira que sua discriminação permite conhecer a origem da cepa.…”