The hepatitis C virus epidemic in Cameroon: Genetic evidence for rapid transmission between 1920 and 1960 Richard Njouom a, * , Eric Nerrienet a,1 , Martine Dubois d , Guillaume Lachenal c , Dominique Rousset a , Aurelia Vessie `re a , Ahidjo Ayouba a , Christophe Pasquier d , Re ´gis Pouillot b a Laboratoire de Virologie, Centre Pasteurdu Cameroun, BP 1274 Yaounde, Cameroon b Laboratoire d’Epide ´miologie et de Sante ´ Publique, Centre Pasteurdu Cameroun, Yaounde, Cameroon c Laboratoire d’Histoire des Sciences (REHSEIS), CNRS-Universite ´ Paris VII, Paris, France d Laboratoire de Virologie, CHU Purpan, Toulouse, France Received 22 March 2006; received in revised form 5 October 2006; accepted 16 October 2006 Available online 29 November 2006 Abstract Hepatitis C virus (HCV) infection in Cameroon is characterized by widespread seropositivity and great virus genetic diversity (3 genotypes and over 10 subtypes). A total of 244 HCV NS5B sequences of 382–405 bp long (95 type 1, 58 type 2, and 91 type 4) were phylogenetically analyzed to estimate the history of the HCV epidemic in Cameroon. The newly developed Bayesian coalescent approach was used to infer the history of each HCV type. The estimated dates of the most recent common ancestors (MRCA) for genotypes 1 (1500; 95% confidence interval (95% CI): 1300– 1650) and 4 (1500; 95% CI: 1350–1700) were in the same range, while the date for genotype 2 MRCA (1600; 95% CI: 1400–1750) was slightly more recent. The mean genetic distance between HCV genotype 1 sequences was greater than that of HCV type 4 sequences, itself greater than that of HCV type 2 sequences. The initial infected populations of all three genotypes did not grow until recently, when they grew exponentially. The growth rate has now begun to slow, with a less steep exponential growth curve. The period of exponential growth of all the three genotypes was between 1920 and 1960. These results (i) confirm that HCV genotypes 1 and 4 have produced long-term endemics, (ii) suggest that genotype 2 was introduced into Cameroon more recently, and (iii) indicate that the exponential spread of the three genotypes between 1920 and 1960 coincided with the mass campaign against trypanosomiasis and mass vaccinations in Cameroon. # 2006 Elsevier B.V. All rights reserved. Keywords: HCV; Epidemic history; Bayesian inference; Iatrogenic transmission; Cameroon 1. Introduction Many of the people of Cameroon (over 10%; Madhava et al., 2002) are seropositive for hepatitis C virus (HCV). This overall estimate does not reflect a high variability: the pattern of infection depends greatly on socio-geographic conditions, increases with age and involves great virus genetic diversity (Delaporte et al., 1994; Kemmegne et al., 1996; Kowo et al., 1995; Louis et al., 1994; Ndjomou et al., 2002, 2003; Ndumbe and Skalsky, 1993; Njouom et al., 2003a,b, 2005; Nkengasong et al., 1995). Moreover, a recent large retrospective and prospective serological study that we conducted on 3500 individuals living in five distinct geographical areas of Cameroon revealed a cohort-effect, indicating large variations in the HCV transmission rate over time (Nerrienet et al., 2005). Research carried out in Egypt demonstrated that the HCV epidemic resulted from the use of non-sterile injection equipment used in parenteral antischistosomal therapy of the general population (Frank et al., 2000; Rao et al., 2002). This was also established by sero-epidemiological and molecular studies (Drummond et al., 2005; Pybus et al., 2003; Tanaka et al., 2004). These molecular studies were conducted using standard analyses of genetic diversity together with coalescent theory (Donnelly and Tavare, 1995; Pybus et al., 2005), which www.elsevier.com/locate/meegid Infection, Genetics and Evolution 7 (2007) 361–367 * Corresponding author. Tel.: +237 223 18 03; fax: +237 223 15 64. E-mail address: njouom@pasteur-yaounde.org (R. Njouom). 1 Present address: HIV and Hepatitis Unit, Institut Pasteur du Cambodge, Cambodia. 1567-1348/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.meegid.2006.10.003