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1. Total population
  • In 2016, 3.5 million people were chronically infected with HCV
2. Current PWID
  • (38.1% to 68%) of current PWID are infected with HCV in 2016
3. Scaling to a population (assuming a growing PWID population)
  • In 2007 there were 2,248,500 PWID (current)

  • Allow PWID (current) population to grow with two model fitting parameters
4. Fit multiplier parameter for force of infection to model increasing incidence of HCV
  • Flat prior to 2009
  • 3 to 4 fold increase in incidence between 2010 and 2018

  • Assume increasing incidence and flattening in 2030 and steady incidence until 2040
5. Fit epidemic model parameters for best fit to 2 to 4. Allow the following model parameters to vary
  • Calibration multiplier for force of infection

  • Relapse (former to current) rate and Injecting career length (current to former)
6. Split of HCV case for PWID (current and former) and general population
  • Fit scenarios around a 60%/20% split

  • Adjust the split such that current PWID account for (74% to 82%) of incident cases

  • MSM and prison populations are not included in this model
7. Number of former PWID
  • Former PWID population with HCV = PWID% (point 6) * 3.5million - fitted pop in 2016 (point 3) * fitted prevalence in point 2
8. Baby boomer effect (contaminated blood) and endemic trend for general population
  • Subjects born in 1945 to 1964 infected from 1970 to 1990

  • Subjects in these age groups have 5 times HCV prevalence compared to other general population age groups

  • Chronic HCV exposure reduces life expectancy on average by 5 years

  • Converting life expectancy reduction to mortality rates

  • Assume that in the general population HCV is endemic, but not an infectious disease

  • So infection is for example from long term blood dialysis, needle sticks, sharps, or mucosal exposures rather than person-to-person exposure (in PWID)
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