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In order to plan the control of hepatitis C in our community, both in the general population and in hospitals, we need a clear picture of the prevalence and changing incidence of the infection in the overall population and in various subgroups.
The prevalence of hepatitis C virus (HCV) infection in the UK general population is not well established. Seroprevalence rates in established blood donors are very low (0.002% )1 indicating a low incidence of infection at the present time, after institution of blood screening and an increased general awareness of HCV in the medical community. However, this is a highly selected population and gives no indication of the prevalence in the general population. New blood donors are also selected, being devoid of groups at high risk of acquiring blood transmitted viruses—in this group the seroprevalence rate is 0.06%.1
In a small study of the general population in south London, the prevalence of HCV viraemia was 0.7%2 and in an unpublished study of the general population examined in a “DOH Look-Back” study in the southwest of England (subjects operated on by a HCV positive surgeon), a prevalence rate of 0.3% was observed. All of these values suggest that although the prevalence of HCV is lower in the UK than elsewhere in Europe and North America, it is still significant, suggesting that there are several hundred thousand people with this persistent infection.
The study of Thorburn and colleagues from Glasgow in this issue ofGut reports that the prevalence in healthcare workers is 0.28%,3 similar to that observed in previous studies in healthcare workers4 5 and in the general population both in Glasgow (0.24%)3 and in southwest England (0.28%), suggesting a low overall rate of transmission from patients to healthcare workers (see page 116). The subgroup analysis showed that the prevalence rate in those carrying out “exposure prone procedures” (invasive procedures where the hands or fingers of the surgeon, nurse, or other staff are in a patient's wound, and where there is a risk of injury to the worker that may result in exposure of the patient's open tissues to the blood of the worker), principally surgeons, was 0.23%, similar to those not involved in these procedures (0.30%) and to the prevalence in the general population (0.28%). In considering only those healthcare workers undertaking exposure prone procedures, the lifetime risk of a UK surgeon acquiring HCV infection was 1.4% (1 in 70) over a surgical career of 35 years (0.04 per 100 person years), similar to that calculated in France (0.3–3.1%).6
What impact do these values have on the assessment of the risk of transmission from healthcare workers to their patients during exposure prone procedures?7 Using the Glasgow values, the risk of transmission from healthcare workers and infection of a patient during exposure prone procedures can be calculated as 1 in 150 000 (the prevalence of HCV infection in healthcare workers (1 in 500)×transmission rate (1 in 300 in the recent DoH “Look-Back” studies, personal communication from Dr Martin Wale)) and the risk of developing chronic infection 1 in 187 500, assuming an 80% rate of viral persistence. The consequences of persistent infection are delayed in that increased liver specific mortality is not seen for 20 or more years and even then it is small (approximately 1 in 50 per year). The risk of dying from HCV infection acquired from a surgical procedure is probably less than 1 in a million, comparable with the risk of being killed by lightning.8
Epidemiology will always be an important approach to the control of disease and HCV is no exception. We know that hospital acquired infection is relatively infrequent and in the general population intravenous drug abuse is an important method of transmission. For the future we need to know much more about how infection spreads in the general community outside of intravenous drug use; in 40% of HCV infected people donating blood in the UK between 1993 and1995, the method of acquisition of the virus was unknown9!
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