Bloodborne pathogensWhile there is some argument over exact timeframes and circumstances (eg. ambient versus laboratory conditions), the main bloodborne pathogens that the community is at risk of, in regards to discarded N&S (Hepatitis B virus (HBV), Hepatitis C virus (HCV), and human immunodeficiency virus (HIV)), can survive outside the human body for several weeks (Thompson 2003). Survival is influenced by the following factors:
- Virus titer
- Volume of blood
- Hepatitis D
- Haemorrhagic fever viruses (eg., Ebola and Lassa)
- In addition, abscesses and even septicaemia can result from a needlestick injury (PSA 2002)
- Direct transmission
- Airborne transmission
- Vehicle borne transmission (eg., from punctures or touching a contaminated item)
- Vector borne transmission
For infection to occur the following is required (DHA 2004):
- a source of infecting micro-organisms or other infectious agent (at a sufficient level to cause infection;
- a susceptible host; and
- a path or transmission for infectious agent to the susceptible host.
Thompson (2003) further indicates that other factors in relation to risk of infection are:
- The prevalence of a bloodborne pathogen with the IDU discarding the N&S
- The type of injury sustained
- The viability of the pathogen outside the human body
- How recently has the N&S been used
- The level of immunity of the person injured
- The use of post-exposure prophylaxis
Table 1 below by Thompson (2003) (modified), summarises the prevalence amongst IDU, major modes of transmission within Australia, potential virus survival and published cases of community transmission.
Gontasezewski (2003), estimates that in Australia, 4.4% of IDU have HIV infections and 65% infected with HCV. Given the longer estimated survival time for HCV, this bloodborne pathogen is probably more of concern in regards to transmission to the community from discarded N&S.
It is suggested that the survival rates for viruses outside the human body does not reflect reality due to the studies determining these times based on laboratory conditions and higher than expected blood volumes and/or virus titers. However, there are studies reporting similar survival times for a range of temperatures. Thus, while the risk of seroconversion following a needlestick injury is unlikely to be zero, the potential for virus transmission of HBV and HCV from a recently discarded N&S is the most likely hazard.
Given the lack of literature on transmission of bloodborne pathogens to the community from discarded N&S in public areas, it is diffi cult to accurately portray the probability and/or demonstrate the potential risks. However, extrapolation from studies that bear some relevance can be used to provide (as best can be determined), best/worst case scenarios and probabilities of seroconversion.
Thompson (2003), states that there have been no published cases of bloodborne virus transmission following community needlestick injury. However, Kermode (2003), states that there has been one documented case of probable bloodborne virus transmission due to a needlestick injury – that of HBV. This occurred in Spain, with a 4 year old boy presented with a history of needlestick injury involving a needle from a neighbour known to be HBV and HIV infected. Other conclusions made in Kermode's paper include:
- No other case of community-acquired transmission of a bloodborne virus has been reported either in Australia or elsewhere.
- A study of 50 community-acquired needlestick injuries (59% occurring in public places), revealed no seroconversion to bloodborne viruses.
- A study in Italy reported no seroconversion to HIV with 408 people following accidental needlestick injury (despite a high percentage of HIV amongst IDU or >50%).
Studies undertaken by Ekwueme (2002), demonstrate the following probability of infections attributed to discarded N&S (used by patients undergoing immunisation), to the community from improper disposal as:
- 0.000003% for HBV
- 0.000001% for HIV.
- 0.000007% for HCV
- 0.0000002% for HIV
A recent study conducted in Australia (Tooher 2005), that reviewed literature relating to waste workers exposure to, seroconversion and/or presence of antibodies to HAV, HBV and Tetanus concluded that there may not be any greater risk to solid waste workers as compared to other waste workers that would be more at risk (eg., sewage waste workers). The authors also concluded that more studies are necessary to arrive at fi rm conclusions.
To gauge what could be considered "worst case" scenario for seroconversion following a needlestick injury, data on such conversions was determined for healthcare personnel and IDU. These two groups have been determined as most at risk due to the potential of the needlestick injury occurring with fresh blood and higher titers of the virus within the blood.
Table 2 below provides data on seroconversion post-needlestick injury in the healthcare setting. While this data shows similar relative percentages, it does illustrate the differences in interpretation of data to arrive at the rates of seroconversion. Thus it can be inferred that each author would also state different (though similar), risk factors for seroconversion following a needlestick injury.
It could be argued that IDU to IDU transmission of bloodborne pathogens is in effect a needlestick injury (though an elective rather than accidental one). Based on this premise, data from the Victorian Department of Human Services illustrate the following. In 2002, 1.7% of those diagnosed with HIV were classified as injecting drug users, 58% with Hepatitis B and 73.4% with Hepatis C (DHS 2003). This data indicates that IDU to IDU transmission of bloodborne viruses is high and that this group does pose a risk to members of the community from discarded N&S. The level of risk, based on the lack of evidence of seroconversion of the community to these bloodborne pathogens, may be deemed to be extremely low.
It must be noted that it is when the syringe is accompanied by an uncapped needle that the risk for infection becomes more probable. This could arise from an accidental encounter (eg. the needle not noticed on the ground), or from a needlestick injury (eg. by picking the needle up to dispose of it or attempting to recap the needle).
In the United Kingdom, a study (Nyiri 2004), found that following laboratory testing of 106 syringes found at four parks in South London. The subsequent testing found that evidence of:
- HBV in 4.7% of syringes
- HCV in 4.7% of syringes
Top of pageHowever, while seroconversion to HIV and HCV has occurred through exposure of fluids onto the skin it is extremely unlikely that this route is of concern to the community from discarded N&S. Russell (2002), reported on studies conducted in Melbourne, Australia that found of 50 cases of a community acquired needlestick injury, there were no seroconversions to HIV, HBV or HCV. These results were also supported in a Canadian study (Slinger 2000) and an Irish study (Nourse 1997). An additional study in New South Wales, Australia, (O'Leary 2003), demonstrated no seroconversions from a community acquired needlestick injury.
Of interest was that, while not conclusive, the article by O'Leary (2003), indicated that the profile of those people most at risk of a community acquired needlestick injury were male and employed as cleaners or police officers.
While extrapolating data from studies undertaken in regards to risks associated with inappropriate disposal of sharps from healthcare facilities, Olowokure (2003), reports that while there are reports of needlestick injury in the community, the risk of infection is lower than that of healthcare facilities. Macalino (1998), supports this due to blood not being "fresh" and in lower volumes in the syringe (than for healthcare facilities).
To put into context, a risk based study conducted (Environment Agency 2002), in the United Kingdom states that the estimated infections resulting from needlestick injuries within the healthcare sector over a 20 year period are (it must be noted that this is probably the highest risk sector in regards to numbers of needlestick injuries and seroconversions):
- HIV – one individual
- Hepatitis B – 32 individuals
- Hepatitis C – 21 individuals
Table 1: Prevalence amongst IDU, major modes of transmission within Australia, potential virus survival and published cases of community transmission by pathogen (Thompson. 2003)
|Pathogen||Prevalence amongst IDU||Major modes of transmission within Australia||Potential virus survival at room temperature||Published cases of community transmission|
Sexual contact IDU
Up to 8 months (no decline in sensitivity)
Up to 8 months (9 fold decline in sensitivity)
Male homosexual contact
Up to 30 days but generally 1-2 days
Table 2: Seroconversion post-needlestick injury in the healthcare setting by pathogen
|Bloodborne Virus||PSA (2002)||CDC (2001)||Heimer (1998)||Collins (1997)|