Estimating the Global Burden of Infections with Bloodborne Pathogens Associated with Unsafe Injections

1
Estimating the Global Burden of Infections with
Bloodborne Pathogens Associated with Unsafe
Injections

• Anja Hauri, Gregory Armstrong, Yvan Hutin
• Safe Injection Global Network Secretariat
• WHO, Geneva

2
Initial Modelling of the Burden of Disease
Attributable to Unsafe Injections Results

• Burden of disease
• HBV infections 8-16 millions
• HCV infections 2.3 - 4.7 millions
• HIV Infections 80,000 to 160,000

Patient with cirrhosis in Africa
Adam Kane et al.
3
Initial Modelling of the Burden of Disease
Attributable to Unsafe Injections Methods
Annual no of injections
Prevalence of susceptibility
P(infection) 1 - (1 - P(susceptible)
P(exposure) P(transmission) )n
Annual probability of infection from injections
Prevalence of active infection x prop of re-use
of equipment
Probability of infection if re-used
syringe/needle
Adam Kane et al. Bull WHO, Oct 1999
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Year 2000 Update of the Global Burden of Disease
Study

• Current and projected burden
• Selected diseases and injuries
• Selected major risk factors (special volume)
• Comparative risk assessment method to study risk
  factors
• Attributable fraction
• Avoidable fraction

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Attributable Fraction

• Proportion of disease that would have been
  prevented in the total absence of exposure
• Obtained though various published formulas using
• The strength of the association
• The proportion of cases exposed
• Provide information about what could have
  happened in the past

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Avoidable Fraction

• Proportion of disease that could be prevented
  through an intervention to reduce exposure
• Obtained through modelling the expected impact of
  reduction in exposure frequency between
• Observed frequency distribution
• Counterfactual frequency distribution
• Provide information about what may happen in the
  future

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Observed and Counterfactual Distributions of
Exposure
Counterfactual minimum distributions
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Input to the model

• Exposure prevalence
• Proportion of the population exposed to a
  contaminated injection
• Injection frequency
• Proportion of re-use
• Epidemiology of infections with bloodborne
  pathogens
• Relative risks
• Relative risk of infection when exposed to a
  contaminated injection
• Based upon
• Relative risks
• Proportion of contaminated injections

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Estimated Annual Ratio of Injections per Capita
by Region
Persons gt 14 years of age
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Proportion of Injections Given with Equipment
Re-used without Sterilization, By Region
Persons gt 14 years of age
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Updated Adam Kane Model
1999
2000 (provisional)
HBV
8,000,000 -16,000,000
32,780,000
2,300,000-4,700,000
HCV
7,043,000
80,000-160,000
98,000
HIV
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Expected Benefit

• World Health Report 2001
• Global burden of Disease 2000
• Special volume on major risk factor
• Basis for cost-effectiveness studies