Zacarias José da Silva

da Silva 2009 da Silva, Zacharias José. 2009. Trends in Retroviral Infections in Guinea-Bissau, West Africa. Cross-sectional surveys and longitudinal community-based studies. Bandim Health Project, Statens Serum Institut. Faculty of Health Sciences, University of Copenhagen.
  Objectives: The aim of this thesis was to describe the spread of retroviral infections in Guinea-Bissau, specifically to evaluate the prevalence of HIV and HTLV, and to identify risk determinants. Furthermore, we assessed the incidences and mortality associated with HIV status and HTLV between 1996 and 2006.

Background: In 1987 the two retroviruses HIV-2 and HTLV was endemic in Guinea-Bissau, having the highest prevalence of HIV-2 in the world. No case of HIV-1 had then been registered. In 1996 HIV-1 had been introduced and the prevalence was 2.3%. Blood screening was implemented in 1987. Retroviral treatment was not available in Guinea-Bissau until recently, after this study was initiated.

Methods: From May 2004 to January 2007, we conducted a HIV and HTLV community-based survey in three adjacent districts of Bissau, Bandim-1, Bandim-2 and Belém. The study population consisted of persons aged 15 years or older from 384 randomly selected houses, of which 296 had been followed since 1996. Blood samples were HIV and HTLV sero-tested at the National Laboratory.

Results: The overall prevalence of HIV-1 and HIV-2 including dual infection was 4.6% and 4.4% respectively, among the 2548 persons included in the study. From 1996 to 2006 there was a doubling of the HIV-1 prevalence from 2.3% to 4.6% and a halving in the prevalence of HIV-2 from 7.4% to 4.4%. The prevalence of HIV-1 increased most among young females (25-34 years old). The prevalence of HIV-2 had decreased for ages below 45 years, but remained high in older ages. The incidence rate in the period 1996-2006 was 0.5 and 0.24 per 100 PYO for HIV-1 and HIV-2 respectively. The incidence rate for HIV-1 had increased compared to the period 1987-96. The incidence rate for younger women (<45 years old) had increased significantly, the incidence rate ratio (IRR) being 2.58 (1.03-6.47).

The prevalence of HIV-1 was higher among Christian females (5.1%) compared to Christian males (2.4%). Muslims males had a higher prevalence compared to males of others religions, PR=1.84 (0.89-3.81). Apart from Muslims, HIV-1 prevalence doubled from 1996 to 2006; for Muslims the prevalence was stable.

Balanta women had a 5-fold higher prevalence compared to Balanta men, and Balanta women compared to Papel women had a higher incidence rate, IRR=5.00 (1.57-15.9). Widows had a higher HIV-1 prevalence compared to single and married women. The prevalence for widows had increased four times between 1996 and 2006, while the prevalence for others had increased two-fold. For men travelling abroad was a HIV-1 risk determinant, and the prevalence had increased 49%.

The prevalence of HTLV-1 was 2.3%. No case of HTLV-2 was found. The prevalence of HTLV-1 decreased from 3.6% in 1996 to 2.3% in 2006. Females had a higher prevalence (2.9%) relative to males (1.5%). The HTLV-1 prevalence increased with age, being 3-fold higher for participants aged 45 years or older compared to participants below 45 years. The prevalence of HTLV-1 was higher among HIV positive (7.7%) compared to HIV negatives (1.8%). The decline of HTLV-1 was independent of HIV status, but higher for HIV-1 infected than HIV-2 infected individuals.

HIV infected had a 2-4 fold increase mortality compared to HIV negative, and generally women had a 30% lower mortality relative to men, independent of HIV status. There was no significant difference in mortality between HTLV infected and uninfected.

Conclusion: The HIV-1 prevalence was 4.6% and is increasing in Guinea-Bissau, while the prevalence of HIV-2 and HTLV-1 is decreasing; however they are still prevalent in the country. The HIV-2 and HTLV-1 prevalences were 4.4% and 2.3% respectively, and are still higher than in most West African countries. Women are most at risk concerning both HIV and HTLV infection. Ethnicity seems to play an important role in the spread of HIV infection in Guinea-Bissau.



Last revised 6 October 2015