Two Distinct Epidemics: The Rise of HIV-1 and Decline of HIV-2 Infection Between 1990 and 2007 in Rural Guinea-Bissau.

van Tienen C, van der Loeff MS, Zaman SM, Vincent T, Sarge-Njie R, Peterson I, Leligdowicz A, Jaye A, Rowland-Jones S, Aaby P, Whittle H.  J Acquir Immune Defic Syndr. 2009 Oct. [Epub ahead of print]

This study set out to assess changes in HIV incidence and prevalence in Caió, a rural area of Guinea-Bissau, between 1990 and 2007. Three cross-sectional community surveys in 1990, 1997, and 2007, were conducted among adults. The prevalence of HIV-1 and of HIV-2 was estimated for each survey, and incidence rates were calculated for the first (1990-1997) and second period (1997-2007). The HIV-1 incidence was approximately 4.5/1000 person-years in the two periods, whereas the HIV-2 incidence decreased from 4.7 (95% confidence interval 3.6-6.2) in the first to 2.0 (95% confidence interval 1.4-3.0) per 1000 person-years in the second period (P < 0.001). HIV-1 prevalence rose from 0.5% in 1990 to 3.6% in 2007, and HIV-2 prevalence decreased from 8.3% in 1990 to 4.7% in 2007. HIV-1 prevalence was less than 2% in 15 to 24 year olds in all surveys and was highest (7.2%) in 2007 among 45 to 54 year olds. The HIV-2 prevalence was fivefold higher in older subjects (>/=45 yr) compared with those less than 45 years in both sexes in 2007. HIV-1 incidence is stable, and its prevalence is increasing, whereas HIV-2 incidence and prevalence are both declining. In contrast with what has been observed in other sub-Saharan countries, HIV-1 prevalence is lower in younger age groups than older age groups.

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Editors’ note: HIV-1 has spread globally while HIV-2 remains confined to West Africa where it is thought to have originated and to countries with socio-economic links to Portugal. HIV-2 has lower sexual and vertical transmissibility, likely due to the lower levels of viraemia seen in HIV-2 infection. This study, the largest community-based study monitoring changes in incidence and prevalence of HIV-1 and HIV-2, found a decline in HIV-2 incidence over an 18 year period and lower HIV-1 incidence and prevalence in 15 to 24 year olds compared with other age groups in this rural area of Guinea-Bissau, suggesting that public health HIV prevention programming from 2002 to 2006 could have influenced risk behaviour among young people. It would be useful to conduct behavioural research and qualitative studies with young people to obtain their views on serological and behavioural findings and what they think has been most effective in protecting them from HIV infection.

Baseline characteristics, response to and outcome of antiretroviral therapy among patients with HIV-1, HIV-2 and dual infection in Burkina Faso.

Harries K, Zachariah R, Manzi M, Firmenich P, Mathela R, Drabo J, Onadja G, Arnould L, Harries A. Trans R Soc Trop Med Hyg. 2009. [Epub ahead of print]

In an urban district hospital in Burkina Faso Harries et al investigated the relative proportions of HIV-1, HIV-2 and HIV-1/2 among those tested, the baseline sociodemographic and clinical characteristics, and the response to and outcome of antiretroviral therapy (ART). A total of 7368 individuals (male=32%; median age=34 years) were included in the analysis over a 6 year period (2002-2008). The proportions of HIV-1, HIV-2 and dual infection were 94%, 2.5% and 3.6%, respectively. HIV-1-infected individuals were younger, whereas HIV-2-infected individuals were more likely to be male, have higher CD4 counts and be asymptomatic on presentation. Antiretroviral therapy was started in 4255 adult patients who were followed up for a total of 8679 person-years, during which time 469 deaths occurred. Mortality differences by serotype were not statistically significant, but were generally worse for HIV-2 and HIV-1/2 after controlling for age, CD4 count and WHO stage. Among severely immune-deficient patients, mortality was higher for HIV-2 than HIV-1. CD4 count recovery was poorest for HIV-2. HIV-2 and dually infected patients appeared to do less well on antiretroviral therapy than HIV-1 patients. Reasons may include differences in age at baseline, lower intrinsic immune recovery in HIV-2, use of ineffective ART regimens (inappropriate prescribing) by clinicians, and poor drug adherence.

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Editors’ note : HIV-2 is thought of as being less pathogenic than HIV-1. People with HIV-2 have a much longer asymptomatic stage, slower progression to AIDS, a slower decline in CD4 count, and lower mortality. So why did this Burkina Faso study find poorer immunological responses to antiretroviral treatment and worse treatment outcomes in adults with HIV-2 infection? Several possibilities deserve further attention. Aside from the fact that people with HIV-1 infection tended to initiate treatment at a much earlier age, 25% of HIV-2 infected patients were given non-nucleoside reverse transcriptase inhibitor (NNRTI) regimens when HIV-2 is naturally resistant to NNRTI. About 38% were also placed on a nelfinavir-containing regimen that has limited virological benefit in people with HIV-2. Matching viral type with treatment regimen is clearly important and it requires correct diagnosis, training, and mentoring along with adequate access to effective antiretroviral drug regimens.