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NIDA. (1999, September 1). Drug Abuse and Addiction Research: 25 Years of Discovery to Advance the Health of the Public. Retrieved from

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Drug Use and Infectious Diseases

The use of illicit drugs is associated with the transmission of HIV/AIDS and other infectious diseases, such as hepatitis B and C and tuberculosis. Furthermore, drug use can result in many other health problems. With the establishment of NIDA's new Center for AIDS and Other Medical Consequences of Drug Abuse, NIDA has the unique opportunity to assess both short- and long-term medical consequences associated with drug use. It has long been known that injection drug use is related to a significant percentage of new AIDS cases each year. More recently, research has indicated that hepatitis C is spreading rapidly among injection drug users, with current estimates indicating infection rates of 65 to 90 percent among this population.

Since AIDS was first identified in 1981, more than 1 million Americans have become infected with HIV. According to the Centers for Disease Control and Prevention, drug use remains the second most common mode of exposure among AIDS cases nationwide. Through June 1997, injection-related AIDS cases accounted for 32 percent of total diagnoses.

Overall and in each age group surveyed, respondents who had used illicit drugs in the past year were more likely than those who had not to have had a blood test for HIV. In addition, illicit drug users were more likely than nonusers to be sexually active and to have had two or more sexual partners within the past year. At the same time, those illicit drug users who reported having two or more sexual partners within the past year were less likely to say that they always used a condom.

Approximately 170,000 new acute hepatitis C virus (HCV) infections occur annually, of which approximately 36 percent are estimated to be related to intravenous drug use. In 1992, the last year for which data are available, the estimated cost of drug use associated with HCV treatment was $429.8 million. HCV is most commonly transmitted through intravenous drug use and blood transfusions and is rarely acquired through sexual contact. In contrast to the epidemiological trends of hepatitis B virus (HBV), the proportion of reported HCV cases acquired through intravenous drug use remains high (12 percent versus 36 percent, respectively). The risk of acquiring HCV through intravenous drug use also increases as the duration and frequency of drug use increases. According to an Australian study, approximately 66 percent of intravenous drug users acquire HBV within 2 years of regular intravenous drug use, and virtually 100 percent of intravenous drug users acquire HCV within 8 years of regular use. However, the results of this study should be used with caution because characteristics of intravenous-drug-user populations (such as needle-sharing) have been shown to vary across and within countries.

Intravenous drug users contract both HBV and HCV by sharing contaminated needles. Studies have shown that intravenous drug users are at high risk to acquire HBV and HCV, as seroprevalence rates range from 65 to 90 percent. During 1993, 12 percent of HBV infections and 36 percent of HCV infections were attributed to persons who used intravenous drugs. These estimates may be conservative because at least 30 percent of adults who reported HBV and HCV cases did not specify a risk factor. It is possible that some persons with unidentifiable risk factors were reluctant to identify intravenous drug use as a risk factor.

As in HIV infection, intravenous drug users can infect not only other intravenous drug users but also their sexual partners. Transmission of HBV through heterosexual activity has been increasing each year, and perinatal transmission of HBV by mothers who use intravenous drugs or have sexual intercourse with an intravenous drug user is common, with transmission rates reaching 90 percent. However, sexual and perinatal transmission of HCV is rare.