Incidence of dual presence of antibodies to HIV1 and HIV2 in seropositive cases seen in Ibadan, Nigeria.

Between July 1987 and December 1988, sera from 6,385 individuals were screened for HIV1 but only 1,861 of these samples were screened for HIV2. Majority of those screened for HIV infection (89.7%) were blood donors, 4.9% were international travellers/volunteers, 3.8% were patients (i.e. those with haematological malignancies, multiply transfused patients and those suspected of having HIV infections), and the rest (1.6%) were female sex workers. Screening for HIV1 antibody was done using Welcozyme anti-HTLV III (Wellcome Diagnostics, Dartford, England) or Elavia I (Diagnostics Pasteur, Marnes La Coquette, France). ELAVIA Ac-Ab-Ak II was used to detect HIV2. The confirmatory test employed was western blot, using LAV Blot I and LAV Blot II (Diagnostic Pasteur, Marnes La Coquette, France). The seroprevalence rate for HIV1 in the blood donors was 0.51% while that of HIV2 was 0.33%. The seroprevalence rates for HIV1 and HIV2 amongst the adult travellers were 1.64% and 0.55% respectively and the comparative rates in the multiply transfused patients (including those with haematological malignancies) were 1.23% each. All the HIV2 positive cases in this group had refractory anaemia. In those suspected of having HIV infection, the seroprevalence rate of HIV1 was 2.94% and no patient in this group had HIV2. Evidence of dual infection by HIV1 and HIV2 was obtained from 18.5% of the seropositive individuals. The dual infection rate in seropositive Nigerians is similar to that reported for some West African countries. We would strongly suggest that all blood samples for HIV tests in Nigerians should be screened for both HIV1 and HIV2. The two blood donors with evidence of dual infection could not be contacted due to fictitious addresses. The only patient with a dual infection has refractory anaemia and he is still being followed up but has not yet developed full-blown AIDs.