HIV risk from sharing needles and injection equipment

The risk per shared injection

When you share a needle or syringe, a small amount of the previous person’s blood can be injected straight into your vein. If that person has HIV and isn’t on effective treatment, CDC estimates the risk from one shared injection at 0.63% (about 1 in 160). That is higher than any kind of sex except receptive anal sex.

Risk adds up when sharing happens often. Ten shared injections with someone who has HIV give a combined risk of about 6.1% (about 1 in 16).

If you don’t know whether the person has HIV, the chance they do is a big part of the picture. Among people who inject drugs, HIV is more common than in the general population. UNAIDS estimates people who inject drugs are about 14 times more likely to acquire HIV than adults in general. For one shared injection with someone in the United States who injects drugs and whose status you don’t know, the estimate is 0.034% (about 1 in 3,000).

It’s not only the needle

CDC notes that HIV and other infections spread through shared syringes and through shared drug preparation equipment. Anything that touches blood or the drug solution can carry the virus, so the safest approach is not to share any of it.

Equipment used days or weeks ago isn’t safe either. In lab tests, live HIV was recovered from blood left in syringes kept at room temperature for more than four weeks (Abdala 1999). How much virus survived depended on how much blood was left inside.

Treatment and U=U

A person with HIV who keeps an undetectable viral load doesn’t pass HIV on through sex. That protection hasn’t been established for sharing needles, so don’t rely on it here.

Harm reduction: what protects you

Use new, sterile equipment every time. This is the single most effective step. Syringe services programs (SSPs), also called needle exchanges, are community programs that provide sterile syringes and injection equipment and safe disposal. Many also offer vaccination, testing, and links to infectious disease care and substance use treatment. CDC describes comprehensive SSPs as safe, effective and cost-saving, and says they play an important role in reducing HIV and hepatitis.

Consider PrEP. PrEP (pre-exposure prophylaxis) is HIV medicine taken before exposure. Taken as prescribed, it lowers the risk of HIV from injection drug use by at least 74%. A clinic can tell you which form of PrEP suits you. With consistent PrEP, the estimate for one shared injection with someone who has HIV drops to 0.16% (about 1 in 610). Sterile equipment still matters on PrEP, because it also protects you from other infections spread by sharing, such as viral hepatitis.

Test regularly. Knowing your status, and encouraging the people you inject with to know theirs, means anyone with HIV can start treatment.

Help with substance use is there if you want it. In the United States, SAMHSA’s free, confidential National Helpline answers 24 hours a day at 1-800-662-HELP (4357) and can point you to treatment services.

What to do now

• If it was more than 72 hours ago, get tested. A lab antigen/antibody test (blood from a vein) is conclusive from 45 days after the exposure. See HIV test accuracy by week.
• If you inject regularly, ask a clinic or SSP about PrEP and where to get sterile equipment near you. More in PrEP and PEP.
• If you have shared many times, the repeated exposures page explains how risk adds up and why regular testing helps.