Epidemiology of Hepatitis C Infection in Canada

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Epidemiology of Hepatitis C Infection in Canada

• Robert S. Remis MD, MPH, FRCPC
• Department of Public Health SciencesUniversity
  of Toronto
• 1st Canadian Conference on Hepatitis CMontreal,
  Quebec
• May 1-4, 2001

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Acknowledgements

• Hepatitis C Transfusion Working Group, June 1998
• Robert S. Hogg, Murray D. Krahn, Robert W.H.
  Palmer, Jutta K. Preiksaitis, Morris Sherman
• in collaboration with
• JoAnne Chiavetta, PhD, Martin Tepper MD, Shimian
  Zou MD and Bob Slinger MD
• HCV-HIV Study, February 2000-March 2001
• Marcel DuBois, Chris Archibald, Jennifer Geduld
• Morris Sherman, Kevin Craib, Shimian Zou
• Others
• Michel Alary, Kevin Craib, Elaine Whittingham

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Background

• Importance of hepatitis C was underestimated due
  to delay in recognizing infection
• difficulties in developing diagnostic tools
• long latency from infection to disease
• Need to better evaluate extent and distribution
  of HCV infection in Canada
• develop appropriate guidelines for primary
  prevention
• develop guidelines for HCV testing
• assess burden of infection and disease in
  shortand long term
• plan appropriate health services and support
  programs

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Overview of presentation

• 1. Review of literature (published unpublished)
• 2. Hepatitis C transmitted by blood transfusion
• 3. Hepatitis C prevalence and incidence in Canada
• 4. Estimating number of persons in Canada with
  dual HCV-HIV infection
• 5. Conclusions

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Selected seroepidemiologic studies among IDUs
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Selected seroepidemiologic studies among
prisoners
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Selected seroepidemiologic studies among patient
populations
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Selected seroepidemiologic studies among
variouspatient populations
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Hepatitis C infection due to blood transfusion
Methods

• Model 1 For each year, number of transfused
  units x HCV risk per unit
• Used survival function to calculate number of
  recipients surviving to July 1998
• Model 2 Estimated number of HCV-infected persons
  in Canada as of July 1998
• Calculated proportion and number due to blood
  transfusion
• Model 3 Estimated number of persons transfused
  in Canada
• Calculated proportion and number with HCV
  infection

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Modeled HCV risk and number of HCV-infected
transfusion recipients, 19801991
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Modeled HCV risk per transfusion episode and
number of HCV-infected transfusion recipients,
1980-1991
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Modeled number of surviving HCV-infected
transfusion recipients by period of
transfusion,19801992
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Modeled number of surviving HCV-infected
transfusion recipients by period of transfusion
(n34,800)
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Modeled number of surviving HCV-infected
transfusion recipients by period of transfusion
19801992
34,790
50
70
420
630
700
900
3,700
5,290
7,660
15,370
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Hepatitis C prevalence and incidence, 1998
Methods

• From HCV transfusion Model 2, estimated
  prevalent HCV infections
• Interpolated to each provinces
• Using population-based data (limited)
• Estimating relative population prevalence from
  first-time blood donors

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Modeled number of HCV-infected persons by
province, 1998 (n240,000)
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Modeled number of HCV-infected persons by
province (n240,000)
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Hypothetical number of HCV-infected persons in
Canada by mode of transmission
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Annual incidence of HCV infection in
CanadaPreliminary perspectives

• Method 1 Observed incidence among populations in
  sentinel surveillance study projected from
  proportion symptomatic to all HCV infections
• Method 2 Observed HCV incidence among
  susceptible IDUs in study cohorts projected
  from proportion IDU to all HCV infections
  (90,000 IDU - 68,000 HCV) x 20
• Preliminary estimate 3,000 - 8,000 new HCV
  infections per year

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HCV infections in CanadaInterpretation

• Estimates are subject to considerable uncertainty
  due to very limited Canadian data from
  representative study populations (only one
  study, in Quebec)
• HCV prevalence appears highest in British
  Columbia, Ontario and Alberta. Four provinces,
  British Columbia, Ontario, Quebec and Alberta
  account for 92 of HCV infections in Canada
• The majority (gt50) of prevalent HCV infections
  in Canada are among IDUs, where HCV prevalence is
  gt100-fold greater than other Canadians taken as a
  whole

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Estimating the number of persons in Canada with
dual HCV-HIV infectionMethods

• 1. Estimate the number of HIV-infected persons by
  HIV-defined exposure category and geographic
  region
• 2. Estimate HCV prevalence in each group (obtain
  data from available studies and review by expert
  consensus panel)
• 3. Multiply number by HCV prevalence
• 4. Plausible limits of outcome using Monte Carlo
  simulation
• 5. Special analysis for Aboriginal population and
  prisoners to estimate persons in each HIV-defined
  exposure category and then as above

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Modeled number of HCV-HIV infected persons by
exposure category, 1999
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Modeled number of HCV-HIV infected persons by
exposure category, 1999 (n11,194)
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Modeled number of HCV-HIV infected persons by
geographic region, 1999 (n11,194)
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Modeled number of HCV-HIV infected Aboriginal
people by exposure category, 1999 (n1,477)
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Modeled number of HCV-HIV infected prisoners by
exposure category, 1999 (n611)
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Conclusions

• Current estimates of HCV infections must be
  considered as hypotheses, not as conclusions
  the epidemiology of HCV infection in Canada
  remains largely unknown.
• Population-based studies are necessary
• Burden of HCV infection is greatest in four
  provinces which account for most HCV infections
  in Canada
• Most new HCV infections are probably among IDUs
  but a substantial proprtion, possibility as many
  as 40, are not related to injection
• Transmission of HCV (probability, determinants)
  in other populations needs further elucidation