Chart shows percentages of at-risk groups in major
"The information further demonstrates that NIDA has a critical role indeed in addressing the drug abuse-HIV connection and in focusing scientific research to understand and deal with the further spread of this devastating disease," he says.
The data confirm earlier figures from periodic CDC reports on the number of newly diagnosed cases of AIDS and HIV infection, which suggested that the proportion of new HIV cases linked to drug abuse was close to one-half. (See "NIDA Plays Key Role in Studying Links Between AIDS and Drug Abuse," NIDA NOTES, May/June 1995)
Dr. Holmberg set out to estimate the size and direction of the HIV epidemic in major U.S. cities with populations greater than 500,000. He compiled a large computer model for tracking disease trends by reviewing more than 350 documents, several large research data sets, and information from 220 public health authorities. Some of the reports date back 10 or more years.
The 96 metropolitan areas Dr. Holmberg looked at have an estimated 1.5 million IDUs, 1.7 million gay and bisexual men, and 2.1 million at-risk heterosexuals. Among these three risk groups there are currently an estimated 565,000 HIV infections, with 38,000 new infections occurring each year. Using these data to make nationwide projections, the review concludes that there are about 700,000 current HIV infections, with 41,000 new HIV infections occurring each year in the U.S. population.
An estimated 19,000 IDUs are infected each year in these 96 metropolitan areas, indicating an HIV incidence rate of about 1.5 infections per 100 IDUs per year, Dr. Holmberg reports. Infection rates are lower for the other two high-risk groups. Although gay and bisexual men still represent the group with the greatest number of current HIV infections, the rate of infection-except in young and ethnic/minority gay men-is much lower now than it was a decade ago, Dr. Holmberg reports. For gay and bisexual men, the HIV infection rate per 100 persons per year is 0.7; for at-risk heterosexuals-those who have sex with IDUs or gay and bisexual men-the rate is 0.5 infections per 100 persons per year. At-risk heterosexual women outnumber at-risk heterosexual men about 4 to 1.
In the research review, HIV incidence rates for metropolitan areas were broken down by estimated numbers of HIV-infected people in each of the three at-risk groups. An estimated HIV infection rate for each group in each city was also provided. "This is highly valuable epidemiological information for better targeting prevention strategies," says Dr. Leshner.
"The HIV epidemic is now clearly driven by infections occurring among injecting drug users, their sex partners, and their offspring," concludes Dr. Holmberg in his review. However, NIDA-funded efforts to educate IDUs to modify their risky drug use behaviors have proven effective, he says. Evidence shows that HIV infection rates in injecting drug users have declined over the past several years in the largest drug-using communities, he reports.
In cities in New York and northern New Jersey, the epicenter of the AIDS epidemic among injecting drug users, many IDUs are switching to practices that may lessen their risk of contracting HIV, such as using sterile, never-used needles and syringes; cleaning needles and paraphernalia; sniffing rather than injecting heroin and cocaine; or abstaining from drug use altogether. This shows that drug abuse and AIDS prevention programs targeting IDUs are working, Dr. Holmberg says.
His review further illuminates the link between the AIDS epidemic and drug abuse as primarily a public health issue. Within this public health perspective, the CDC scientist's review also provides important insights for policymakers, clinicians, and administrators who are planning and implementing drug abuse and HIV prevention and treatment programs. Targeting HIV treatment and prevention programs to IDUs also holds potential for reducing the spread of other blood-borne infections, including hepatitis B and C viruses.
Holmberg, S.D. The estimated prevalence and incidence of HIV in 96 large U.S. metropolitan areas. American Journal of Public Health 86(5):642-654, 1996.
From NIDA NOTES, March/April 1997
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