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NIDA. (1999, August 1). Infectious Diseases and Drug Abuse. Retrieved from

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August 01, 1999

Drug abuse involves health risks that often are as dangerous as the physiological effects of the drugs themselves. Injecting drug users (IDUs) are at high risk for direct exposure to a variety of blood-borne bacterial and viral infections. As a result, drug users are more likely than nonusers to contract a variety of infectious diseases and, when infected, to progress to serious illness and death.


Injection drug use has been responsible for more than one-third of all adult and adolescent AIDS cases reported in the U.S. since the beginning of the AIDS epidemic, according to the Centers for Disease Control and Prevention (CDC) in Atlanta. More than one-half of all preadolescent AIDS cases in the U.S. have resulted from a transmission chain whereby a woman contracts HIV as a result of injection drug use and passes the disease to her child during pregnancy or birth. Of adult and adolescent AIDS cases, approximately 32 percent were among IDUs, and another 4 percent involved heterosexual sex with an IDU. During 1998, approximately one-third of all new AIDS cases in the U.S. were related directly or indirectly to injection drug use (See chart for a breakdown of the injection drug use-related cases).

1998 AIDS Cases Related to Injection Drug Use1998 AIDS Cases Related to Injection Drug Use

Noninjection drug use can also contribute to HIV transmission. Studies have shown that inner-city youths who smoke crack cocaine are up to three times more likely to be infected with HIV than are inner-city youths who do not. Noninjecting drug users who trade sex for drugs or who engage in unprotected sex while under the influence of drugs increase their risk of infection.


Hepatitis B (HBV) and hepatitis C (HCV) are viral diseases that destroy liver cells and can lead to cirrhosis and liver cancer. People can become infected with HBV through sexual intercourse with an infected person or through exposure to an infected person's blood, as may happen when IDUs share needles. Blood transfusion and needle sharing are the most common routes of infection with HCV. NIDA-supported research has shown that the risk of infection by HBV and HCV is extremely high in the first year after beginning injection drug use. One study found overall HCV and HBV prevalences of 76.9 percent and 65.7 percent, respectively, in a group who had been injecting drugs for 6 years or less.


Tuberculosis (TB) is transmitted from person to person by airborne bacteria. This disease is most prevalent in crowded low-income areas with substandard health conditions. Drug users are from two to six times more likely to contract TB than nonusers. CDC estimates that in 1996 at least 11 percent of new TB cases were in drug users with noninjecting drug users twice as likely as IDUs to contract the disease. Compared to others with TB, IDUs are more likely to develop the disease in multiple organs and sites, rather than only in the lungs.

Other Infectious Diseases

Drug users have a high incidence not only of HIV/AIDS but also of other sexually transmitted diseases including syphilis, chlamydia, trichomoniasis, gonorrhea, and genital herpes. The geographic distribution of syphilis and gonorrhea infections across the U.S. reflect the geographical distribution of the use of crack cocaine and its associated high-risk behaviors, such as unprotected sex and the exchange of sex for drugs.

Among IDUs, the most common cause for medical treatment is skin infection at the site of injection. Complications from these infections range from skin ulcers and localized abscesses to stroke, botulism, tetanus, destruction of lung tissue, and infection of the heart valves.

Bacterial and Viral Infections

Associated with injection drug use can progress to systemic infections and damage any system. Directly observed medication therapy, in which the patient takes medications in the presence of a health care provider, is generally recommended for addicts, many of whom may have difficulty following treatment regimens.