There are two answers depending on what you mean by "needle." If you mean the kind used for sewing, this is very different from a needle attached to a syringe. A sewing needle would not be able to transmit HIV very easily because the tiny bit of blood left on the needle would be exposed to oxygen and low temperatures. HIV cannot survive outside the body unless it is sealed within a container. Therefore, a pin prick, like the malicious cases reported in India, even if they were tainted with HIV, would be an extremely inefficient means of infection. Even health care workers who are stuck with needles and medical instruments have a very low rate of infection (only 0.3%).
If, however, you are talking about a syringe, the scenario you describe would be similar to sharing a drug needle and would be a very efficient means of transmitting HIV and other diseases. What makes it risky is that blood from the infected person is drawn up into the syringe and then injected into the next person. The more blood transfused in this way, the greater the risk of infection. When injecting a substance into the body using a syringe, both health care workers and drug users will insert the needle and then pull back on the plunger to see if they have hit a vein. Even when injecting a vaccine into an arm or the butt muscle, health care workers routinely pull back to make sure they are not in a vein. When they are aiming for a vein they do the same thing to make sure they are in fact in the vein. Either way, this means that blood enters the syringe and several microliters will probably remain in the tip of the syringe after the syringe is emptied. For drug injectors, this blood residue can also infect the water and the cotton which are often shared when "cooking" the drug mixture.
In an ideal world, the best way to avoid contamination would be to dispose of the needles so they are never used again. Because needles are scarce, thanks to the ban on federal funding of needle exchange, most needle exchange programs can only afford a one-for-one exchange. As a result, many needles are reused by the same person and many are shared with, or "rented," to others.
In Geneva, last month I ran into, Robert Heimer, an expert on the viability of HIV inside syringes. I asked him how long the virus could remain infectious in a used syringe. Inside the hermetically sealed syringe, HIV can remain viable for up to 36 days, depending on the type of syringe and the amount of virus it contained to begin with. Syringes with detachable needles, your basic insulin needle and the most common type exchanged by needle exchange programs, can contain about 20 microliters of residual blood. In syringes with fixed needles the residue is only about one microliter, and as a result, HIV doesn't last as long in the fixed needle syringes.
Rinsing the syringe with full-strength bleach is the best way to inactivate the virus. It is unclear how long the bleach must stay in the syringe to inactivate the virus. According to Heimer, studies with syringes containing 50 microliters of HIV infected blood (much more than the usual 1 to 20 microliters of blood left in the syringe) showed that it took 30 seconds to inactivate HIV. But Hepatitis is even hardier than HIV. Syringes should be bleached for at least two minutes to neutralize both HIV and hepatitis. One technique would be to fill the syringe with bleach and shake it up and down for about the time it takes to sing "La Bamba". A similar technique has been dubbed the "syringe cha cha cha" by workers at San Francisco's Prevention Point. The syringe should be rinsed again with clean water before shooting up. Survival of Human Immunodeficiency Virus (type-1) in Injection Syringes.
Clay SP; Heimer R; Jariwala Freeman B; Negioanu D; Griffith B. Int Conf AIDS, 1996 Jul 7-12, 11:1, 355 (abstract no. Tu.C.2522)
Abstract Objectives: (1) To develop and deploy a whole blood quantitative microculture assay (WBQMA) able to utilize the small volumes of blood remaining in injection syringes after use. (2) To determine the duration of survival of HIV-1 in injection syringes. (3) To determine the viral load in syringes over the survival period. (4) To discern policy implications of the findings. Methods: A whole blood quantitative microculture for HIV-1 was developed and standardized to current PBMC quantitative culture techniques. Multiple syringes were loaded with blood infected by two wild-type strains of HIV-1 and stored in simulation of street use in accordance with ethnographic studies. Contents were removed at Day 0 through Day 28 and were cocultured with uninfected PBMCs for a maximum of 21 days. Testing for p24 AG in the supernatant, using Abbott kits, was conducted for viral load calculation. Statistical analysis included Chi Square, Median Test, and the Bonferroni Method for Multiple Comparisons. Results: Viable HIV-1 was cultured from syringes stored for as long as 28 days. 50% of Strain VS001- and 99% of VS002-loaded syringes were positive for viable virus; the overall syringe positivity rate was 75%. The two strains differed from one another by number of syringes positive per time of storage and by storage time specific viral loads (p is less than 0.05 and p is less than 0.01 respectively). Loads on Days 0, 1, 3, 7, 21, 28 differed (p is less than 0.05) from Day 14. Conclusions: (1) The WBQMA is capable of quantifying viral load from small inputs. (2) A 28-day survival time exceeds current estimates. (3) Load appears to be sufficient to effect transmission. (4) This survival time provides a scientific basis for needle exchange and supports the use of harm reduction techniques and the removal from circulation of used syringes and injection equipment. Back to: Questions sorted by topic |
