High HIV prevalence amongst injecting drug users in Valencia

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The proportion of individuals undergoing HIV testing in Valencia who received a positive result fell significantly between 1988 and 2003, according to an article published in the online edition of Sexually Transmitted Infections. Declines were seen in all HIV risk categories. Nevertheless, almost a quarter of all injecting drug users tested HIV-positive, and the investigators observed an increase in HIV incidence in gay men from 2001 onwards.

Few data are available on HIV infection trends over time in Spain. Therefore investigators from the Centre for AIDS Information and Prevention (CIPS) in Valencia, Spain, undertook a study to determine trends in HIV testing, serial HIV prevalence and HIV incidence in Valencia between 1988 and 2003. Their study sample included all 21,241 individuals who had an HIV test at a CIPS clinic in Valencia.

A little over two-thirds of the individuals attending for an HIV test were men, 27% were injecting drug users, 43% were heterosexuals, and 13% were gay men.

Glossary

sample

Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

maintenance therapy

Taking drugs for a period of time after an infection has been treated, to stabilise the condition or prevent a re-occurrence or deterioration.

Between 1988 and 1990, injecting drug users accounted for the majority (57%) of clinic attendees, but this fell to 14% of total attendances by 1997 – 2003. At the same time as attendances by injecting drug users fell, there was an increase in the number of heterosexuals requesting an HIV test, and by 1997 – 2003, a total of 56% of all individuals undergoing HIV testing were heterosexuals. The proportion of gay men attending for HIV tests remained stable over the 15 years of analysis.

A total of 3,234 individuals tested HIV-positive, representing an HIV prevalence of 15% for the entire study period. But HIV prevalence fell significantly over time. Between 1988 and 1990, prevalence was 35%, but there was a year-on-year fall thereafter, and by 1999 prevalence had fallen to 10%, and it fell to 3% by 2003.

Despite this overall fall, HIV prevalence amongst injecting drug users remained high: 26% in 2003.

The highest HIV prevalence observed in gay men was 25% in 1990. This was followed by a steady decline, and by 2003 the HIV prevalence amongst gay men had fallen to 6%.

Prevalence amongst heterosexuals peaked at 11% in 1988 and 1991, but by 2003 had fallen to 2%.

Repeated HIV tests were performed on 4,424 individuals and 340 of these were positive.

HIV incidence peaked in 1988 at 6%, and then fell dramatically in all HIV risk groups before peaking again at 8% in 1995. The 1995 peak was followed by another overall fall in incidence for all risk groups, but the investigators noted with concern a significant increase in HIV incidence amongst gay men from 2001 onwards.

The investigators attribute decreased HIV prevalence amongst drug users to prevention efforts such as methadone maintenance therapy and needle exchanges.

Although the investigators describe the apparent increase in HIV incidence amongst gay men as “worrying”, they suggest that this statistic should be treated with caution and write that it could “reflect either ineffective HIV prevention messages…or the use of HIV testing”.

Other countries in western Europe have experienced an increase in heterosexual HIV prevalence due to migration from high prevalence countries. Such increases are not supported by the data from Valencia which show decreases in both heterosexual prevalence and incidence.

References

Hurtado I et al. Trends in HIV testing, serial HIV prevalence and HIV incidence among people attending a Center for AIDS Prevention from 1988 – 2003: increases in recent years in HIV incidence in men who have sex with men. Sexually Transmitted Infections (online edition), 2006.