Discarded needles

When injecting drug users or other people leave used needles or syringes in public places, this can often lead to anxieties and concerns about the risk of HIV transmission. In parks, play areas, beaches, public toilets or streets, people may step on discarded needles or children may handle them. Refuse workers are also at risk of coming into contact with discarded needles.

Moreover, studies have shown that HIV can survive in syringes for up to six weeks,^1,2 while hepatitis C can remain detectable for two months.³ Virus is more likely to survive when there are lower temperatures, greater volumes of blood and within larger syringes.

There have only been two reported incidents of blood-borne viral infections thought to be due to discarded needles. One was a case of hepatitis B in a child,⁴ the other of hepatitis C in an adult.⁵

There have been no reported cases of HIV infection through contact with a needle discarded in a public place.

A review of the literature up until September 2007, conducted by the Canadian Paediatric Society, identified twelve case series (articles describing what happened to a series of individuals who had had contact with discarded needles). Each came from an area of high prevalence of blood-borne viruses, in a range of countries. These involved a total of 483 children who had follow-up testing for HIV, 452 children who tested for hepatitis B and 265 tested for hepatitis C. Only a minority of children (130) received post-exposure prophylaxis (PEP) for HIV. There were no infections for any blood-borne virus.⁶

Subsequent to this, clinicians in Montreal published the largest single case series yet to describe the outcomes of contact with discarded needles.⁷ Beginning in 1995, 274 paediatric patients (aged 0 to 18) had presented to hospitals in the city after being injured by a needle. Most of the children had picked up or played with a needle (64%), while 9% had stepped on one. A quarter of the children had an injury which bled, but the needle or syringe was reported to have visible blood in just 13% of cases.

Eighty-two children took post-exposure prophylaxis for HIV. In the 189 children who came back for HIV testing six months later, none were HIV positive, whereas HIV prevalence in Montreal injecting drug users is 16%. Moreover, no child tested positive for hepatitis B or C.

The Canadian Paediatric Society⁶ note a number of reasons why injuries from discarded needles in community settings are less likely to lead to HIV infection than injuries in healthcare settings: injury does not occur immediately after the needle was first used; the needle rarely contains fresh blood; any virus present has been exposed to drying and environmental temperatures; and injuries are usually superficial.

Although infection is theoretically possible, they consider that “it is extremely unlikely that HIV infection would occur following an injury from a needle discarded in a public place.”

They recommend that the following factors are considered when making an assessment of the risk of HIV transmission:

• Source: consider the prevalence of HIV among injecting drug users in the local area.
• Device: consider the size of needle, whether it is hollow-bore, presence of visible blood in the needle or syringe, probability of exposure to drying, heat and freezing since use. Larger devices with visible blood are highest risk.
• Injury: consider depth and extent of trauma (scratch or deep cut, injection of blood and bleeding at the site). Injuries with actual blood injection are high risk. Superficial scratches are low risk.

Post-exposure prophylaxis for HIV is only recommended in cases where there is a high risk of HIV transmission. But post-exposure prophylaxis for hepatitis B, vaccination for hepatitis B and vaccination for tetanus is recommended in a larger number of situations.

In the UK, draft guidelines on HIV post-exposure prophylaxis from BASHH and BHIVA do not recommend the provision of PEP following injury with a needle discarded in a community setting. At the time of writing (October 2011), the final version of the guidelines has not been issued.