Epidemiologic studies of HIV/AIDS and drug abuse
Categories: Drug AbuseDRUG ABUSE BEHAVIORS ASSOCIATED WITH AIDS
Drug abuse, and particularly intravenous drug abuse (IVDA), is an important factor in transmission of the human immunodeficiency virus (HIV). Since HIV is transmitted via infected blood and other body fluids, the common practice among IVDAs of sharing needles facilities the transfer of the virus. High risk sexual activity, too, increases the chance of drug abusers becoming infected with HIV and subsequently infecting others.
In order to fully delineate the connection between drug abuse and HIV, it is necessary to examine scientific information from both disciplines. Therefore, this article will review the status of epidemiologic studies concerning both the acquired immunodeficiency syndrome (AIDS) and drug abuse (focusing on IVDA). We will review reported AIDS cases, HIV seroprevalence studies of IVDAs, and surveys of drug abuse. We will critique several ongoing studies and suggest additional opportunities for epidemiologic research.
AIDS AMONG INTRAVENOUS DRUG ABUSERS
Between June 1981 and September 30, 1990, 152,126 cases of AIDS were reported to the Centers for Disease Control (CDC). In the last year (October 1989-September 1990), about 120 new cases of AIDS were reported to the CDC each day. This represents a 25% increase over the previous year (October 1988-September 1989). Approximately 29% of the AIDS cases in adults are among IVDA. Heterosexual IVDA accounts for 22% of all AIDS cases, whereas homosexual and bisexual IVDA account for an additional 7% of all cases. Twenty percent of all male cases were heterosexuals who reported using needles for self-injection of drugs not prescribed by a physician at least once prior to developing AIDS. Fifty percent of all females with AIDS reported such a drug abuse history.
The risk for AIDS in the drug-abusing community is not limited to those individuals who personally inject drugs illegally. Fifty-one percent of heterosexual AIDS cases were attributed solely to heterosexual contact with an IVDA. HIV infection among IVDA and their sexual partners is an important reservoir of infection and provides a conduit for infection for others in the heterosexual community. Children of drug abusers are also becoming infected with HIV during pregnancy and in the perinatal period. Fifty-one percent of the mothers of children with perinatally acquired AIDS reported a history of IVDA, and another 20% reported heterosexual contact with an IVDA [1].
As high as these figures are, they do not fully reflect the connection among heterosexual contact, drug abuse, and AIDS. For surveillance purposes, AIDS cases are categorized according to a hierarchy of risk factors. An AIDS patient reporting any intravenous drug use since 1977 is categorized as an intravenous drug abuser whether or not needles were shared. Some patients may have acquired the virus via heterosexual contact rather than through the use of contaminated injection paraphernalia.
In addition, many cases now listed as “undetermined” may actually be linked with HIV transmission to heterosexuals via sexual contact with IVDUs. For example, many male AIDS patients with “undetermined” risk admit to sexual contact with prostitutes or with a wide variety of heterosexual partners. If a patient does not know whether any sexual partner was an intravenous drug abuser and does not fall into other categories, the case is classified as “undetermined” rather than “heterosexual.”
SEROPREVALENCE STUDIES AMONG INTRAVENOUS DRUG ABUSERS
The number of AIDS cases does not adequately describe the extent of the problem of HIV among IVDUs. Because of the long latency period from infection with HIV to diagnosis of AIDS [2,3], and the persistence of infectivity of HIV-antibody positive individuals [4], the number of infected individuals would be a better measure of the extent of the epidemic among IVDA. However, social and political concerns preclude comprehensive HIV antibody testing at this time, thus limiting its utility for surveillance purposes in the United States.
A few general statements about HIV seroprevalence rates can be extrapolated from selected studies. Some caveats in regard to interpretation of the data are in order, however. Seroconversion rates may not always be reliable indicators of seroincidence. Most studies do not address possible changes in their study populations over time. Rates of refusal to participate in a study should be calculated and reported. Nevertheless, the following studies are reported as probably indicative of trends in seroprevalence among IVDAs.
The seroprevalence of HIV infection in a population of IVDA increases over time once infection has been introduced. This was illustrated by Des Jarlais et al. [5] who examined seroprevalence trends among IVDAs entering drug abuse treatment programs in Manhattan. In sera collected in 1978, 1/11 (9%) were HIV positive. This rose to 13/50 (26%) in 1979, 8/21 (38%) in 1980, and 14/28 (50%) between 1981 and 1983. From 1984 through 1987, seropositivity rates seemed to stabilize between 55 and 60%. In another, earlier study, Novick and colleagues [6] studied heterosexual men and women in New York City who were current or former IV heroin abusers, were on methadone maintenance, and were enrolled in a study of chronic liver disease. Stored sera from participants were tested for HIV antibody. In 1978, 0/7 sera were HIV positive; for 1979, 14/49 (29%); for 1980, 8/18 (44%); for 1981-83, 14/27 (52%); and 56% (numerator and denominator not included in report) in 1984.