9261 HEPATITIS C REPORT GALLEY - North West Public Health ...

The high prevalence of infection among IDUs means that, when sharing needles or
other injecting equipment occurs, the probability of sharing with an infected individual
is very high. Furthermore, infection among IDUs occurs very quickly; the risk of infection
for each year of injecting has been estimated at between 15% and 30% (Rezza et al.
1996; Hagan et al. 1999), but results of a recent Australian study suggest that the risk
may be as high as 80% per year injecting in younger users (van Beek et al. 1998).
Compared to HIV, hepatitis C is transmitted in blood relatively easily. For example, the
probability of becoming hepatitis C positive following a needlestick injury (3% to 9%)
is ten times higher than with needlesticks involving HIV (0.3%) (Coutinho 1998). Thus,
although the length of time since onset of injecting behaviour is a strong predictor of
hepatitis C infection, a large proportion of users get infected within a year or two of
beginning injecting (e.g. Smythe et al. 1998; Lamden et al. 1998). Furthermore,
because of its infectivity, it is not only sharing needles that poses a risk, but also
syringes, spoons, filters, water; in other words any material used for the preparation of
the drug and potentially shared between users (collectively called paraphernalia)
(Renton & Main 1996). This ease of transmission and persistence of infective particles
increases the probability that those injecting in the presence of other injectors will come
into contact with the virus even if the user is taking fairly stringent precautions.
There has been a degree of behaviour change (such as not sharing needles) among IDUs
towards adopting safer injecting practice in order to avoid HIV infection (Stimson 1995).
However, the same awareness and behavioural change is yet to be realised for other
injecting equipment. Thus, many studies report a high prevalence of sharing injecting
equipment: for example 94% of IDUs in Berlin had shared syringes more than one
hundred times (Stark et al. 1996) and among British IDUs, 80% had shared some form of
injecting equipment in the last month (Hunter & Stimson 1998). Even if the probability of
contracting hepatitis C after a single occasion of sharing paraphernalia is relatively low,
the likelihood of infection can become high if such sharing behaviour is frequent.
Seventy percent of people currently living with hepatitis C have had their infections
attributed to injecting drug use, 10% to blood products, 2% to occupational exposure
(i.e. needlestick injuries), up to 2% to household contact, 1-2% to tattooing and related
procedures and up to 1% to sexual contact, with many of the remaining cases having an
unknown route of transmission (Dolan 1997). This high proportion of unattributed cases
remains an enigma in the study of the epidemiology of hepatitis C. Unlike HIV and
Hepatitis B, transmission of hepatitis C through sex appears to be relatively rare
(Zylberberg et al. 1999). For example, spouses of haemophiliacs infected with hepatitis C
do not appear to be infected at a higher rate than the general population (Brackmann et
al. 1993; Thomas 2000). Hepatitis C virus particles have been isolated from the semen of
infected men in some studies but not others (Semprini et al. 1998; Zylberberg et al.
1999). Although case studies suggest that sexual transmission is possible, the actual risk
appears too low to be accurately quantified (Renton & Main 1996). In the rare cases
H EPATITIS C IN INJECTING DRUG USERS IN THE N ORTH W EST
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