Epidemiology of hepatitis C virus infection among injecting drug users in Australia

Modelling the hepatitis C virus epidemic in Australia. Hepatitis C Virus Projections Working Group

INTRODUCTION

In Australia, to the end of 1997, more than 110,000 people have been diagnosed with hepatitis C virus (HCV) antibodies and reported to State/Territory surveillance systems. The available data indicate that the overwhelming majority (around 80%) of people with HCV antibodies were infected through injecting drug use.

METHODS

Models of the HCV epidemic in Australia were developed based on estimates of the pattern of injecting drug use in Australia. Estimates of HCV infections due to injecting drug use thus obtained were then adjusted to allow for HCV infections resulting from other transmission routes. Projections of cirrhosis and hepatocellular carcinoma (HCC) resulting from HCV were obtained by combining modelled HCV incidence with estimates of the progression rates to these outcomes.

RESULTS

Based on the models, it was estimated that there were 196,000 (lower and upper limits of 149,000 and 234,000) people in Australia living with HCV antibodies at the end of 1997, with HCV incidence in 1997 estimated to be 11,000 (8500-13,500). It was estimated that 8500 (4000-13,000) people were living with HCV-related cirrhosis in 1997 and that there were 80 (40-125) incident cases of HCV-related HCC.

DISCUSSION

Model-based estimates were broadly consistent with other sources of information on the HCV epidemic in Australia. These models suggest that the prevalence of HCV-related cirrhosis and the incidence of HCV-related HCC will more than double in Australia by 2010.

Assessment of long-term outcomes of hepatitis C virus infection in a cohort of patients with acute hepatitis in 1971-1975: results of a pilot study

BACKGROUND

To examine the long-term effects of hepatitis C virus (HCV) infection in a cohort of patients admitted to Fairfield Hospital with hepatitis from 1971 to 1975. The availability of stored sera from this time enabled testing to identify those who were anti-HCV positive on admission.

METHODS

Sixteen per cent (n = 230) of the cohort tested positive for HCV antibody (anti-HCV). The 'unexposed' group was selected from those who were anti-HCV negative. Systematic approaches were used to locate the cohort and health outcomes assessed by a study specific questionnaire and clinical review with repeat serology and liver function tests.

RESULTS

Complete follow up has been achieved on a subset of 35 HCV-seropositive and 70 seronegative individuals. The seropositive group was significantly more likely to have given a history of injecting drug use, the presumed route of infection. The seropositive group was also more likely to have elevated serum alanine aminotransferase levels, but only two (6%) were known to have progressed to cirrhosis.

DISCUSSION

The anti-HCV-positive individuals followed up to date are at increased risk of liver-related pathology, but few had progressed to cirrhotic liver disease. This differs from findings of transfusion-related studies and suggests, within the limitations of the study, that the natural history of community acquired HCV may be more benign.

A computer model of the spread of hepatitis C virus among injecting drug users

A number of behavioural and clinical parameters influence the transmission of an infectious agent through direct contact between two individuals. The behavioural parameters encountered in such situations are also likely to exhibit an enormous amount of variability. With the spread of hepatitis C among injecting drug users, the parameters associated with injecting behaviour play an important role in the modelling of the transmission process. Computer simulation modelling is an ideal approach to deal with a large number of parameters as well as high levels of variability without excessive simplification. The simulation model presented in this paper is tested on data from a cohort of injecting drug users and the results obtained are very encouraging from a public health perspective. The model clearly indicates that the rate at which HCV spreads through a population of injecting drug users is extremely sensitive to the interaction rate and to the probability of infection through a single contact with an infective. At the same time it shows that rate of spread is not very sensitive to initial prevalence, which is very encouraging from a public health perspective.

The prevalence of hepatitis C in patients admitted with acute hepatitis to Fairfield Infectious Diseases Hospital, 1971-1975

OBJECTIVE

To identify and determine trends in the prevalence of hepatitis C virus (HCV) antibody in stored sera from 1971 to 1975 and to determine associations with HCV seropositivity, including markers for other hepatitis infections and possible routes of transmission.

DESIGN

A retrospective cross-sectional study.

PATIENTS AND SETTING

1511 adults admitted to Fairfield Infectious Diseases Hospital, Victoria, with a clinical and biochemical diagnosis of hepatitis between 1 January 1971 and 31 December 1975.

MAIN OUTCOME MEASURES

Prevalence over study period of hepatitis A virus antibody (anti-HAV) IgM, hepatitis B core antibody (anti-HBc), hepatitis B surface antigen (HBsAg) and hepatitis C virus antibody (anti-HCV) in stored sera; sociodemographic data and risk factors for blood-borne viruses documented in original medical records.

RESULTS

Anti-HCV was detected in 17% of adults admitted with hepatitis from 1971 through 1975. Prevalence increased significantly over this period. Most cases were in young men who had a history of injecting drug use. HCV seropositivity was also significantly associated with markers for hepatitis B infection.

CONCLUSIONS

Given the 20-30-year period between infection with hepatitis and the development of liver disease, our findings predict significant liver-related morbidity in Australia in the next decade. The increase in prevalence over the five years studied suggests rapid spread of HCV through susceptible populations, principally injecting drug users.

Vietnamese-speaking injecting drug users in Melbourne: the need for harm reduction programs

While research on aspects of injecting drug use (IDU), including injecting and sexual risks for HIV transmission, has been progressing in 'mainstream' Australian populations, there has been little among non-English speaking background (NESB) communities in Australia, particularly the South-East Asian communities, of which the Vietnamese is the largest. This exploratory study employed and trained peer workers to recruit and interview IDUs of Vietnamese origin in Melbourne on a wide range of subjects related to risks associated with their drug using, as an initial assessment of risk-taking behaviours for blood-borne viruses among Vietnamese-speaking IDUs. A finger-prick blood sample was taken where possible to measure antibody status to HIV, HBV and HCV. The profile which emerged was not dissimilar to that of their English-speaking counterparts prior to the benefit of currently available harm-reduction programs. A relatively isolated group whose social world often related only to other Vietnamese-speaking drug users, they were engaging in unsafe sex and unsafe injecting and were unfamiliar with procedures for cleaning injecting equipment and where they could seek out information and services, including needle exchanges. This study has identified an urgent need not only to promote currently available information and services to this group, but also to provide culturally relevant education and other harm-reduction measures needed to prevent transmission of HIV, other BBVs and STDs. The study has highlighted the lack of responsiveness of mainstream health services to the needs of Vietnamese-speaking IDUs.