Brennan and colleagues1 published a paper entitled ‘Epidemiology of Hepatitis C in Ireland’ in EPI-INSIGHT in May 2004.  The authors collated information on hepatitis C from a variety of sources1. In Ireland there is no estimate of the prevalence of hepatitis C among the general population.  According to the Irish Blood Transfusion Service,1 the prevalence of hepatitis C among new donors decreased from 0.06 per cent in 1997 to 0.01 per cent in 2004; this decrease reflects changes in eligibility criteria for blood donation rather than a true decrease among the population.  The prevalence of HIV and hepatitis B among the general population was three times that among new blood donors living in Dublin. There is no reason not to believe that a similar risk ratio between new blood donors and the general population exists for hepatitis C. 

The prevalence estimates among injecting drug users attending community-based drug services range between 52 per cent and 84 per cent (Table 1). 2–6  Hepatitis C is endemic among injectors in prison; the prevalence of hepatitis C antibodies among injector-inmates and entrants was 81 per cent7 and 72 per cent8 respectively (Table 1).   

Allwright et al.7 and Long et al.8 (2001) reported that injecting drug use was the most important risk factor for hepatitis C. Allwright et al.7 (2000) and Smyth et al.9 (2003) reported that spending time in prison prior to testing was associated with an increased risk of testing positive for hepatitis C antibodies.  Length of time injecting appears to be strongly associated with contracting the infection.2,3,4,7 For example, among drug users attending Trinity Court Drug Treatment Centre the prevalence of hepatitis C was 52 per cent among those injecting for less than 25 months, compared to 84 per cent among those injecting for 25 months or more. Also, the prevalence of hepatitis C was 65 per cent among prison inmates injecting for less than 36 months, compared to 85 per cent among those injecting for 36 months or more.2 Injecting practices such as injecting frequency and sharing needles were also associated with testing positive for hepatitis C.7,8

Table 1   Review of studies estimating the prevalence of hepatitis C among injecting drug users in Ireland

  a Following initial infection with hepatitis C, antibodies to this virus develop on average three months after infection but may take up to six months to develop. The presence of hepatitis C antibodies (anti-HCV) indicates either previous or current infection.

 Since January 1 2004 there is a statutory requirement to notify both laboratory and clinical diagnosis of hepatitis C.10  Up to the end of 2003, there was a statutory requirement to notify clinical cases of viral hepatitis type unspecified (also known as non A and non B) to the public health departments in each health board.  Since mid 2000, the type of hepatitis was notified when hepatitis C was the cause of hepatitis and it was observed that the vast majority of cases had this virus type.1  From 2001 to 2003, just over 80 cases of hepatitis C were notified each year.  In 2002, approximately 85 new cases of hepatitis C were reported to public health departments through the clinical notifications system, while the National Virus Reference Laboratory reported 1,233 new hepatitis C antibody cases in the same year.  This suggests serious under-reporting of clinical cases, which should be rectified under the new statutory instrument.  The notification system does not allow us to identify risk factors so it is unclear how many of these cases were injecting drug users.  This indicates the need for an extended notification process for hepatitis C.  

 Between 1992 and 1998, Smyth et al. estimated the incidence of hepatitis C among 100 injecting drug users who had an initial negative test and a repeat test within 24 months.9 The authors reported that the incidence of hepatitis C was 66 per 100 person years (95% CI 51 to 84 per 100 person years); this is 30 per cent higher than estimates reported in injecting drug users living in other countries. 

 There were 6,085 discharges from acute hospitals with hepatitis C as a primary or secondary diagnosis recorded by the Hospital In-Patient Enquiry Scheme.1  This scheme is an event- based register so cases may be represented more than once. 

Of the 6,085 cases:

• 18 per cent had hepatitis C as a primary diagnosis;
• 57 per cent had chronic hepatitis C;
• 21 per cent had a diagnosis of problem opiate use;
• 7 per cent also had a diagnosis of hepatitis B recorded;
• 24 per cent also had a diagnosis of HIV/AIDS recorded;
• 11 per cent had a diagnosis of chronic liver disease or sequelae;
• 0.4 per cent had a diagnosis of liver cancer.

These data suggest the existence of co-morbidity between blood-borne viruses and the damage that hepatitis C can do to the liver.  

Brennan and colleagues1 requested the Central Statistics Office to select cases where the primary cause of death was hepatitis ICD 9 category 070.4, 070.5 or 070.6.  This allowed the authors to calculate the number of deaths with a primary diagnosis of hepatitis C using the diagnoses hepatitis ‘other specified’ or ‘unspecified’ as proxy diagnoses. Fifty persons died as a result of hepatitis C between 1995 and 2002.  Up to 2001, the numbers for each year fluctuated between three and seven cases, with a rise to 15 cases in 2003.  The main risk factors for hepatitis C cannot be identified accurately through mortality data held by the Central Statistics Office.  This suggests the need for a special register to record the contribution of hepatitis C to premature mortality among injecting drug users.

Taken together, these data suggest hepatitis C is endemic among injecting drug users and it has serious health consequences which can be seen in both morbidity and mortality statistics.   

1. Brennan A, Thornton L, Connell J, O’Neill W, O’Riordan J (2004) Epidemiology of Hepatitis C infection in Ireland. EPI-INSIGHT, 5 (5):2-4. 
2. Smyth R, Keenan E and O'Connor JJ (1995) Hepatitis C infection among injecting drug users attending the national drug treatment centre. Irish Journal of Medical Science, 165(4): 267–268.
3. Smyth R, Keenan E and O'Connor JJ (1998) Blood-borne viral infection in Irish injecting drug users. Addiction, 93(11): 1649–1656.
4. Smyth B, Keenan E and O'Connor JJ (1999 a) Evaluation of the impact of Dublin's expanded harm-reduction programme on prevalence of hepatitis C among short term injecting drug users. Journal of Epidemiology and Community Health, 53: 434–435.
5. Cullen W, Bury G, Barry J and O’Kelly F (2000) Drug users attending general practice in the Eastern Regional Health Authority area. Irish Medical Journal, 93(7): 214–217.
6. Fitzgerald M, Barry J, O'Sullivan P and Thornton L (2001) Blood-borne infections in Dublin's opiate users. Irish Journal of Medical Science, 170(1): 32–34.
7. Allwright S, Bradley F, Long J, Barry J, Thornton L and Parry JV (2000) Prevalence of antibodies to hepatitis B, hepatitis C and HIV and risk factors in Irish prisoners: results of a national cross-sectional survey. British Medical Journal, 321; 78-82
8. Long J, Allwright S, Barry J, Reaper-Reynolds S, Thornton L, Bradley F and Parry JV (2001) Prevalence of antibodies to hepatitis B, hepatitis C and HIV and risk factors in entrants to Irish prisons: a national survey. British Medical Journal, 323: 1209–1213.
9. Smyth B, O'Connor JJ, Barry J, Keenan E (2003) Retrospective cohort study examining incidence of HIV and hepatitis C infection among injecting drug users in Dublin. Journal of Epidemiology and Community Health, 57: 310–311.
10. Changes to Notification of Infectious Diseases (January 2003)

   The paper ‘Epidemiology of Hepatitis C in Ireland’ is available on the National Disease Surveillance Centre website at https://www.drugsandalcohol.ie/12916/