For most of us, our only experiences with needles are in medical settings where technicians wearing protective gloves give us an injection or draw blood. We watch as the technician carefully disposes of the sharp in a bright red container with a label that states in large letters: INFECTIOUS WASTE BIOHAZARD. Sharps containers are present in all medical settings because used needles are categorized as a biohazard and so stringent regulations dictate safe disposal practices.
It is very unsettling for members of the public, then, that public health officials seem to downplay the hazard created by used needles that are improperly disposed of in public spaces. If strict medical protocols are in place to avoid needle stick injuries (NSIs), don’t these improperly discarded needles constitute a danger to the public?
Many blood borne pathogens and substances, such as illegal drugs or contaminants, can be transmitted through needle stick injuries but the three transmittable viruses that are the focus of research on needle stick injuries are human immunodeficiency virus (HIV), hepatitis B (HBV) and hepatitis C (HCV).
Most research on NSIs involves injuries to health care workers (HCW), including janitorial workers. The reported rate of NSIs among HCWs is fairly high and definitely much higher than the rate of NSIs reported by the general community. This makes sense as many HCWs use or are exposed to needles every time they go to work.
Using data from health care workers, the U.S. Public Health Service, estimates that the risk of contracting HIV through a percutaneous injury (needle puncture) is 0.3%. (1) This means that for every 1000 needle stick injuries, three will result in HIV infection. Hepatitis B (HBV) is the virus most easily transmitted through NSIs. Estimates vary with the CDC estimating 6-30% chance of contracting HBV from an NSI. More specifically, the risk varies with the source of the infection. Blood that is positive for two HBV surface antigens can result in clinical hepatitis B in 22-31% of NSIs but blood that is positive for only one antigen results in clinical hepatitis in 1-6% of NSIs. Estimates for contracting hepatitis C (HCV) from an NSI vary. Typically, an estimate of approximately 2% is cited for seroconversion to HCV infection from an NSI although one study estimated that the risk of hepatitis C virus transmission from a single NSI with hepatitis C virus RNA-positive blood was 10%. (2)
So what does all this NSI data collected from health care workers mean for people in the general community?
Extrapolating the statistics for NSIs involving health care staff to NSIs in the general community has several limitations. On the one hand, the needles that HCWs come in contact with are more likely to contain fresh blood and therefore are more likely to transmit infectious pathogens than are needles found discarded in the community. On the other hand, health care workers are aware of the possibility of a needle stick injury and so the degree to which NSIs are underreported by HCWs is likely very low. In addition, unlike victims of community acquired needlestick injuries, HCWs are more likely to be able to determine the source patient of the blood and have information as to the infectious status of the person. It is very likely that the number of needle stick injuries among community members is significantly under-reported. This is especially true for children, who might not realize the danger presented by discarded needles. Immigrants, especially those with limited English, are another group among whom NSIs are likely underreported. Many immigrants work in jobs, such as gardening, housekeeping, and sanitation, where they might be exposed to a needle that was not properly disposed of.
It is possible to become infected with a virus as a result of a community acquired needlestick injury as there have been documented cases (as reported by Papenberg et al, 2008).
One study of community acquired needlestick injuries (CA-NSIs) incurred by children (3) estimates the maximum rate of contracting HIV, HBV, or HCV from a CA-NSI to be 1.6%, 1.8%, and 1.9% respectively. The children in this study did not show evidence of serologic conversion, however, almost 25% did not have follow-up testing and the children who were tested were offered prophylactic (preventative treatment). The authors also note that HBV surface antigen, HCV RNA, and HIV DNA and RNA have been detected in discarded syringes found in community settings. For one study (4), researchers collected a total of 106 syringes in South London over a 4 month period and found evidence of HCV (4.7%) and HBV (4.7%). Another study found that HBV can survive in dried blood for at least one week. (5)
The statistics discussed above do not convey the whole picture.
The good news is that many people are vaccinated for HBV and that prophylactic treatment for HBV and HIV now exists. (A prophylactic is a medication or a treatment designed and used to prevent a disease from occurring)
The bad news is that;
1) there is no post exposure prophylaxis for HCV (hep c);
2) not all people who suffer needle stick injuries seek medical care and so the rate of infection is not only likely under-reported, but also testing and prophylactic treatment are not made available to these individuals;
3) testing and prophylactic treatment is expensive and, even if affected individuals have health insurance, they will likely be responsible for deductibles, copays and coinsurance;
4) a needle stick injury and the subsequent testing and treatment are anxiety provoking for both the person who experienced the needle stick injury and their family members; and
5) prophylactic treatments are not without risks and side effects and are not 100% effective.
The chance of virus transmission varies with each injury. Deeper punctures and the presence of fresh blood in the syringe are two factors that increase the likelihood of viral transmission. However, for liability reasons, the medical profession will almost always choose the safest option and people who suffer a needle stick injury will have the burden of making the decision on whether or not to opt out of prophylactic treatment.
- The small number of studies on community acquired needlestick injuries and likely under-reported by those who experience a needle stick injury (NSI) limit the preciseness of estimates of the chance an NSI will lead to disease transmission.
- The chance that a community acquired NSI will lead to transmission of HIV, HBV, or HCV is low.
- However, testing and prophylactic treatment (available for HIV and HBV but not HCV) is anxiety provoking, constitutes a financial burden for many individuals, is not without side effects, and is not always effective.
- Better needle exchange protocols, such as a strict 1:1 exchange, would best balance the public health interest of preventing transmission of disease in intravenous drug users while reducing the chance of a community acquired NSI.
1) U.S. Public Health Service Working Group. Updated US Public Health Service Guidelines for the Management of Occupational Exposures to Human Immunodeficiency Virus and Recommendations for Postexposure Prophylaxis in Infection Control and Hospital Epidemiology on August 6, 2013 (ICHE 2013; 34(9):875-892). Available at: http://stacks.cdc.gov/view/cdc/20711. Accessed 2/29/16.
2) Mitsui, T., Iwano, K., Masuko, K., Yamazaki, C., Okamoto, H., Tsuda, F., Tanaka, T. and Mishiro, S. (1992). Hepatitis C virus infection in medical personnel after needlestick accident. Hepatology, 16: 1109–1114. doi:10.1002/hep.1840160502
3) Papenburg et al. (2008). Pediatric injuries from needles discarded in the community: Epidemiology and risk of seroconversion. Pediatrics, 2008; 122;e487. Available at: http://www.academia.edu/942640/. Accessed 2/29/16.
4) Nyiri, P., Leung, T., & Zuckerman, MA. (2004). Sharps discarded in inner city parks and playgrounds-risk of bloodborne virus exposure. Communicable Disease and Public Health. 2004 Dec.; 7(4): 287-8. Available at: http://www.ncbi.nlm.nih.gov/pubmed/15779791. Accessed 2/29/16.
5) Bond WW, Favero MS, Peterson NJ, Gravelle CR, Ebert JW, Maynard JE. (1981). Survival of hepatitis B after drying and storage for one week. Lancet 1981;1:550-1.
The following article was written by a Public Health Researcher at the request of the Needles Solutions Team.