Epidemiology
Mehendale SM, Gupte N, Paranjape RS, Brahme RG, Kohli R, Joglekar N, Godbole SV, Joshi SN, Ghate MV, Sahay S, Kumar BK, Gangakhedkar RR, Risbud AR, Brookmeyer RS, Bollinger RC. Declining HIV Incidence Among Patients Attending Sexually Transmitted Infection Clinics in Pune, India. J Acquir Immune Defic Syndr. 2007;45(5):564-9.
A recent report suggesting declining HIV transmission rates in southern India has been based on HIV seroprevalence data to estimate HIV incidence. We analyzed HIV incidence rates among 3 cohorts (male, female non-sex worker, female sex worker [FSW]) presenting to sexually transmitted infection (STI) clinics in Pune, India over 10 years. Between 1993 and 2002, consenting HIV-uninfected individuals were enrolled in a prospective study of the risks for HIV seroconversion. Standardized HIV incidence estimates were calculated separately for the 3 cohorts. RESULTS: HIV acquisition risk declined by more than 70% for female sex workers (P = 0.02) and men (P < 0.001) attending the STI clinics. There was no significant reduction in HIV incidence among women attending STI clinics (P = 0.74). The decline in HIV acquisition risk among male patients with STIs was associated with an increase in reported condom use with recent female sex worker contact and a decrease in genital ulcer disease. We report the first direct evidence for a decline in HIV incidence rates in FSWs and male patients with STIs over time. The lack of change in HIV infection risk among non-sex worker women highlights the need for additional targeted HIV prevention interventions.
Editors’ note: Many estimates of incidence are based on HIV prevalence data. Here is concrete cohort-derived evidence of declines in HIV incidence over a 10 year period which are associated with increased condom use in commercial sex transactions – a 70% decline for sex workers and men attending sexually transmitted infection clinics. Reduced genital ulcer disease likely played a contributing role. Changing the conditions under which sexual services are bought and sold, by making condom use the norm, creates significant impediments for HIV and interrupts chains of transmission.
Ghys P, Zaba B, Prins D. Survival and mortality of people infected with HIV in low- and middle-income countries: results from the extended ALPHA network. AIDS 2007;21(suppl 6):S1–S4
Published at a time when antiretroviral treatment (ART) is rapidly being scaled up in most low- and middle-income countries, this paper introduces a collection of papers representing a major collaborative effort to quantify and analyse the survival from HIV seroconversion to death in the absence of ART. The advent of effective treatment means it will not be possible to conduct any further studies of this nature in the future, so the results from these analyses together with a small number of previously published survival studies will serve as a baseline against which to assess the impact of ART in low- and middle-income countries. In addition, this new information is important for deriving parameters to model HIV epidemics. These joint analyses suggest that the survival of people infected with HIV in low- and middle-income countries is broadly similar to survival in developing countries before ART became available, and that the survival functions are closer than previously believed. Based on the new evidence the UNAIDS Reference Group on Estimates, Modelling and Projections recommended that, for the purpose of modelling national epidemics, the assumption about average net survival in most low- and middle-income countries be changed from 9 years to 11 years, and be kept at 9 years in countries where subtype E is dominant. The new survival assumption has resulted in lower estimates of numbers of new HIV infections and AIDS mortality in many countries, and this is reported in the 2007 AIDS Epidemic Update report. This constitutes an example of the rapid incorporation of new evidence in the methodology for HIV infection and AIDS mortality estimates.
Editors’ note: Estimates of the burden of HIV infection, morbidity, and mortality that are used to keep track of the evolution of the epidemic need to be based on research findings. This supplement presents the new evidence that was rapidly incorporated into the estimation methods and assumptions which underpin the latest UNAIDS/WHO estimates. The latest estimates are on the UNAIDS website at www.unaids.org/en/HIV_data/2007EpiUpdate/default.asp
Gilbert MT, Rambaut A, Wlasiuk G, Spria TJ, Pitchenik AE, Worobey M. The emergence of HIV/AIDS in the Americas. Proc Natl Acad Sci U S A. 2007;104(47):18566-70
HIV-1 group M subtype B was the first HIV discovered and is the predominant variant of AIDS virus in most countries outside of sub-Saharan Africa. However, the circumstances of its origin and emergence remain unresolved. Gilbert and co-authors propose a geographic sequence and time line for the origin of subtype B and the emergence of the HIV pandemic out of Africa. Using HIV-1 gene sequences recovered from archival samples from some of the earliest known Haitian AIDS patients, the authors found that subtype B likely moved from Africa to Haiti in or around 1966 (1962–1970) and then spread there for some years before successfully dispersing elsewhere. A "pandemic" clade, encompassing the vast majority of non-Haitian subtype B infections in the United States and elsewhere around the world, subsequently emerged after a single migration of the virus out of Haiti in or around 1969 (1966–1972). Haiti appears to have the oldest HIV epidemic outside sub-Saharan Africa and the most genetically diverse subtype B epidemic, which might present challenges for HIV-1 vaccine design and testing. The emergence of the pandemic variant of subtype B was an important turning point in the history of AIDS, but its spread was likely driven by ecological rather than evolutionary factors. Based on their results, Gilbert and co-authors suggest that HIV-1 circulated cryptically in the United States for 12 years before the recognition of AIDS in 1981.
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