Background. HIV-1 infection emerged in Central Africa 50 to 60 years ago from a simian source (SIV_cpz from chimpanzees). At least 3 cross-species transmission events have occurred, generating groups M, N, and O. All 3 HIV-1 groups are co-circulating in Cameroon. The mechanism of HIV emergence is unknown. One theory explaining the mechanism and the timing of HIV-1 emergence proposes that multiple unsterile injections facilitated the cross-species transmission and fueled the spread of HIV in humans. In this regard, we have investigated the risks of HIV transmission by injections in a rural Anglophone region of Cameroon.

Methods: To examine the extent of contamination of injections in Kumba, Cameroon, we observed the circumstances of a sample of injections (n = 1500+) administered in a range of clinical settings in a three month period in 2001-2002. Plasma, cells, and matched syringe washes from these injections were collected and tested by Determine (Abbott) rapid test and Inno-Lia Immunoblot (Innogenetics). HIV RNA was extracted from positive and indeterminate samples and from syringe washings. PCR assays were performed to amplify gag, pol, and env genes. HBV (HBsAg) and HCV seroprevalence was tested by ELISA (Ortho), whereas their presence in needle washes was investigated by PCR.

Results: A high prevalence of blood-borne viral pathogens was observed in this rural area of Cameroon, with prevalences of 16.92%, 10.75%, and 10.12% for HIV, HBsAg and HCV, respectively in adults. False negative rapid test (Determine) results were characterized by early seroconversion profiles by Inno-Lia and positive PCR being thus due to a high incidence of HIV rather than to the circulation in the area of divergent strains. All sequenced viruses were group M, belonging mainly to the CRF_02 (IbNg) (>50%). Subtypes A, D, F2 and CRF11_cpx were also present. Only syringe washes from i.v. injections (32 % of the total) tested positive by PCR, and sequence analyses showed that the viral form was CRF_02.

Conclusions: A high prevalence of blood-borne viruses in rural Cameroon was found. In this region, the reliability of serological surveys may be influenced by high incidence of HIV. The limited diversity of the strains present in the syringe washes may be related to biological properties of CRF_02. Reuse of blood draw syringes and lack of testing of blood for transfusion may have fueled the massive expansion of CRF_02 in West Central Africa and contributed to SIV human infection.

Keywords: HIV diversity; Cameroon; i.v. injections