PERSISTENT HYPERENDEMICITY OF HEPATITIS C VIRUS INFECTION IN TAIWAN: THE IMPORTANT ROLE OF IATROGENIC RISK FACTORS

The purpose of this study was to investigate determinants of
endemic hepatitis C virus (HCV) infection within
communities in Taiwan. A two-phase study, including a
seroprevalence survey and a prevalent case-control study at
the first phase, which has been published previously, and a
follow-up seroconversion determination and an incident case-
control study during the second phase, was carried out to
evaluate correlates of persistent endemic HCV infection. At
the first phase, a total of 12,021 men and 1,819 women who
were 30-64 years old and living in seven townships in Taiwan
were tested for the seroprevalence of antibodies to HCV (
anti-HCV). In addition, a prevalent case-control study
involving 272 HCV-positive cases and 282 seronegative
controls identified from the anti-HCV testing was conducted
to investigate risk factors associated with HCV prevalence.
During the second phase, a total of 2,728 men and 834 women
who were seronegative at recruitment participated in the 1-
year prospective study on anti-HCV seroconversion.
Subsequently, an incident case-control study based on 39
seroconverters and 81 persistently seronegative controls
were carried out to elucidate determinants of HCV
seroconvertion, Antibodies to HCV were tested by the second-
generation enzyme immunoassay. Information on risk factors
of HCV infection was collected from subject interviews. The
prevalence of anti-HCV consistently increased with age (
range 2.9-5.4%), whereas no apparent age trend was observed
for anti-HCV seroconversion rate (range 0.9-1.7%). A
striking geographical variation in seroprevalence and
seroconversion rates of anti-HCV was observed in the study
townships. Furthermore, a significant geographical
correlation between HCV seroprevalence and seroconversion
rates was noted (r=0.962, P=0.001). From the results of both
prevalent and incident case-control comparisons, medical
injections were found to be the main mode to sustain the
persistent endemic state of HCV infection within a community
(odds ratios for prevalent and incident case-control studies
were 2.5 (95% Cl = 1.7-3.6) and 3.1 (95% Cl = 1.4-7. 1),
respectively. The data indicate that the basis for HCV
transmission has already been existed in study areas and the
iatrogenic risk factor tended to be the major determinant
for sustaining persistent endemicity within a community. (C)
2001 Wiley-Liss, Inc.