By: Kylie E C Ainslie, Caroline Walters, Han Fu, Sangeeta Bhatia, Haowei Wang, Marc Baguelin, Samir Bhatt, Adhiratha Boonyasiri, Olivia Boyd, Lorenzo Cattarino, Constanze Ciavarella, , Zulma Cucunubá, Gina CuomoDannenburg, Amy Dighe, Ilaria Dorigatti, Sabine L van Elsland, Rich FitzJohn, Katy Gaythorpe, Lily Geidelberg, Azra C Ghani, Will Green, Arran Hamlet, Katharina Hauck, Wes Hinsley, Natsuko Imai, David Jorgensen, Edward Knock, Daniel Laydon, Gemma Nedjati-Gilani, Lucy C Okell, Igor Siveroni, Hayley Thompson, Juliette Unwin, Robert Verity, Michaela Vollmer, Patrick GT Walker, Yuanrong Wang, Oliver Watson, Charles Whittaker, Peter Winskill, Xiaoyue Xi, Christl A Donnelly, Neil M Ferguson , Steven Riley

In: Report 12, the WHO Collaborating Centre for Infectious Disease Modelling within the MRC Centre for Global Infectious Disease Analysis, J-IDEA, Imperial College London.

Date: 26 March, 2020

Summary 

• Project the health impact of the pandemic in 202 countries.
  • 182 out of 202 countries now have reported cases.
  • Use age-specific contact patterns and COVID-19 severity data.
• Large degree of variation among countries, regions and economic status.
  • Differences in age-profile, distribution of co-morbidities, age-specific contact patterns and social mixing.
• These differences have material consequences for transmission and the associated burden of disease.
  • Variation in the extent to which infection spreads to the older, more vulnerable members of society.
• Varying factors reviewed include:
  • Age demographics (high income countries -> older populations, low income countries -> younger populations).
  • Prevalence of other infectious diseases (higher in low income countries).
  • Average size of households with resident over 65 years old (substantially higher in low income countries).
  • Contact patterns between age groups (steeply decline in high income countries).
  • Healthcare capacity (obviously worse in low income countries).
• Compare global predicted mortality:
  • Unmitigated epidemic.
    • 7 billion infections (range: 6.4-.7.2 billion).
    • 40 million deaths globally (range: 35-42 million).
    • Ro of 3.0 (range: 2.4-3.3).
  • Mitigation A (see below).
    • 33% less infections than no mitigation (range: less by 30-38%).
    • 24 million deaths (39% less than no mitigation, range: less by 19-55%).
  • Mitigation B:
    • 20 million deaths (49% less, range: less by 23-67%).
  • Suppression:
    • 1.9 – 10.5 million deaths.
      • Lower number start suppression strategy when there are 0.2 deaths per 100,000 per week.
      • Higher number: start at 1.6 deaths per 100,000 per week.
• Lower income countries predicted to have less severe disease, hospitalization and deaths.
  • Mainly due to younger average age.
  • But, lack of healthcare facilities and difference in co-morbidity prevalence may drive low income country numbers higher.
• As per previous study, mitigation strategy leaves healthcare systems overwhelmed.
  • 25x capacity at peak.
  • Especially in lower income countries (about 7x for high income countries).
• Need early and wide-spread implementation of suppression strategy:
  • Testing, isolation of cases, wider social distancing.
• Same caveats as before:
  • Social and economic costs and impact high and not take into consideration here.
  • Suppression strategy needs to be in place for a long time (until there is a vaccine).
• Scenarios and assumptions:
  • Unmitigated epidemic.
  • Mitigation A.
    • Uniform reduction in social contacts (about 44%).
  • Mitigation B.
    • Elderly: shielding (60% reduction in social contacts).
    • Wider population: interrupting transmission (40% reduction in social contacts)
  • Suppression.
    • Uniform 75% reduction in social contacts.
    • Start suppression when weekly death rate per 100,000 exceeds 0.1, 0.2, 0.4, 0.8, 1.6, or 3.2 deaths per week per 100,000 population.
• Fatalities for unmitigated epidemic and suppression by region: