Early outbreak context

  • within a few days / weeks of index case
  • limited data available
  • no or limited intervention
  • no depletion of susceptibles
  • urgent assessment needed to inform response

Data usually available

  • dates of symptom onset

  • contact data: exposure (who infected you?) and contact tracing (who could you have infected?)

  • dates of exposure / infection

  • dates of outcome: death / recovery

  • metadata on patients: age, gender, location, occupation, etc.

  • data from past outbreaks

Key questions

Disease-dependent, but generally includes:

  • How fast is it growing?
  • What is driving the epidemic growth?
  • What is the case fatality ratio?
  • Who is most severely affected?
  • How many cases should we expect in the next days / weeks?

Refresher on statistics

Some basic definitions

  • population: set of all possible observations of a given process/entity
    example: all possible cases of cholera in location xxx
  • sample: subset of the population
    example: all cases of cholera in xxx reported last week
  • a statistic: quantity used to describe sample / population
    example: % of fatalities in cholera cases in xxx last week
  • inference: statement about population(s) from sample(s)
    example: % of fatalities in cholera cases in xxx is greater than in yyy

Population, sample, uncertainty