Study: Virus may live up to four weeks in syringes

Researchers simulate illicit drug-use conditions

HIV-1 cells that are capable of reproducing can survive in syringes for up to four weeks, say researchers who claim the study highlights the importance of government-sponsored needle-exchange programs to reduce the spread of HIV through drug addicts sharing dirty needles.

If HIV-1 can survive for more than two weeks in a syringe, then it could be spread quickly among an addict community, as research has shown that people in some cities reuse and share needles seven or more times, on average.1 When states or cities ban needle-exchange programs, addicts may use needles for even longer periods of time.

"It tells us that needle-exchange programs are effective," says Nadia Abdala, PhD, a post-doctorate associate and researcher in the department of public health at Yale University School of Medicine in New Haven, CT. Abdala co-wrote the study, published in January in the Journal of Acquired Immune Deficiency Syndromes and Human Retrovirology.

Needle-exchange programs reduce the circulation time of syringes and prevent people from sharing them, Abdala says. When needles were distributed, collected, and tracked by a New Haven syringe exchange program, investigators found that the average circulation time of syringes was seven days at the start of the exchange program, but it dropped to less than three days once the program was fully operational.1

Previous studies have attributed three out of 10 cases of AIDS to the use of HIV-1-contaminated syringes during illicit drug use.1,2

Drug users can contaminate needles when the plunger is withdrawn until blood becomes visible in the barrel of the syringe, which ensures that the syringe is inserted into a vein. In a worst-case scenario, which is what the study simulated, a drug user will pull up on the plunger a second time, introducing blood into the barrel of the syringe that mixes with the remaining drug solution.

Researchers worked on experiments and preliminary studies for two years, Abdala says. They found that infectious HIV can survive for as long as four weeks inside a syringe that contains one or two microliters of blood, Abdala says.

The study used a microculture assay that was sufficiently sensitive for the propagation of HIV-1 from small volumes of whole blood.

Study simulations based on field reports

"We worked with people who work in the field and have direct contact with injection drug users," she says. "They report what practices drug addicts are using, and we used simulations in the lab to try to repeat what they were doing."

The study also reported these findings:

    • Syringes with detachable needles are riskier for HIV transmission because they harbor more blood between the plunger and the base, and when the needles are replaced it can extend the life of the syringes.

    • Further studies should examine whether postinjection flushing with clean water may significantly lessen the chance of HIV-1 transmission when clean syringes and bleach are unavailable.

    • The experiments showed that the likelihood of encountering a potentially infectious syringe decreased with time, and the risk increased if the volume of infected blood was larger.


    1. Abdala N, Stephens PC, Griffith BP, Heimer R. Survival of HIV-1 in syringes. J Acquir Immune Defic Syndr Hum Retrovirol 1999; 20:73-80.

    2. Centers for Disease Control and Prevention. HIV/AIDS Surveillance Report 1997. Atlanta.