Needlestick injury: HIV risk and what to do

First aid, right now

CDC’s guidance for workers who are stuck by a needle or splashed with blood is:

1. Wash needlestick wounds and cuts with soap and water.
2. Flush splashes to the nose, mouth or skin with water.
3. Rinse eyes with clean water, saline or a sterile eyewash.
4. Report the incident to your supervisor.
5. Get medical care right away so a clinician can assess the risk.

How big is the risk?

If the needle had just been used on someone with HIV who wasn’t on effective treatment, CDC estimates the risk from one needlestick at 0.23% (about 1 in 430). That figure comes from studies of healthcare workers.

Some features of the injury make it more likely. A large study of healthcare workers (Cardo 1997) found that each of these raised the odds several-fold:

• A deep injury. The calculator multiplies the odds by 15. For a deep injury from a needle used on someone with HIV, that gives 3.3% (about 1 in 30).
• Visible blood on the needle or device, odds multiplied by 6.2.
• A needle that had been in a vein or artery, odds multiplied by 4.3.

When several apply, the calculator uses the largest one rather than multiplying them together.

When you don’t know whose needle it was

Most needlesticks involve someone who doesn’t have HIV. If the source person’s status is unknown, the chance they have HIV matters as much as the injury itself. For a needlestick from someone of unknown status in the United States, the estimate is 0.00092% (about 1 in 110,000). At work, it may be possible to test the source person with their consent, which can settle the question quickly.

Needles found in public

A needle found in a park, on a beach or in a bin is a common worry, especially for parents. The risk is usually very low: the person who used it would need to have HIV, and the needle would need to contain their blood. But it isn’t zero. In lab tests, live HIV was recovered from blood left inside syringes kept at room temperature for more than four weeks (Abdala 1999), so an old needle isn’t automatically safe.

Treat it like any other needlestick. Wash the wound, then get medical advice the same day. CDC advises against testing the needle itself: the results aren’t reliable, and handling it risks another injury. If it’s still lying there, tell your local council or health department so it can be removed safely.

What happens at the clinic

A clinician will ask how the injury happened, how deep it was, and what is known about the needle and its source. They will usually test your blood at the start, and may also test for hepatitis B, which can spread through needlestick injuries too.

If the risk is high enough, you’ll be offered PEP: HIV medicines taken daily for 28 days. PEP must start within 72 hours of the injury, and the sooner the better. Started within 24 hours, the calculator estimates it lowers the risk by about 90%. After 72 hours, PEP is no longer recommended. If you take PEP, follow-up HIV tests are usually at 4 to 6 weeks and 12 weeks after the injury.

At work

Report every injury to your supervisor, however small, so you can be assessed quickly and the injury is on record. Your workplace’s exposure plan should tell you where to go, day or night. Ask for a copy of what was recorded.

What to do now

• Under 72 hours: wash, report, and get assessed for PEP today.
• Over 72 hours: PEP is no longer recommended, but testing is still worth doing. A lab antigen/antibody test (blood from a vein) is conclusive from 45 days after the injury. The HIV test accuracy by week page shows when each test is reliable.
• Feeling anxious? That’s normal. For most needlesticks the risk is small, and a test after the window period gives you a definite answer.