The use of epidemiological tools in conflict-affected populations: open-access educational resources for policy-makers

Table of Contents

1. Welcome
2. Introduction: Epidemiology in crises
3. Ethical issues in data collection
4. Need for epidemiologic competence
5. Surveys - Introduction
6. Surveys - Description of sampling methods
7. Surveys - Sampling error, bias, accuracy, precision, & sample size
8. Surveys - Resources required for surveys
9. Surveys - Critiquing survey reports
10. Surveillance - When to do surveillance
11. Surveillance - Methods
12. Surveillance - Common problems
13. Programme data
14. Rapid assessment
15. Mortality - Indicators and their measurement
    1. Why measure mortality
    2. Parts of mortality rate
    3. Formats for mortality rate
    4. Types of mortality rates
    5. Mortality rates for children
    6. Number of excess deaths
    7. Measurement of causes of death in surveys
16. Mortality - Data sources
17. Mortality - Interpretation and action
18. Nutrition - Introduction and background
19. Nutrition - Indicators and their measurement
20. Nutrition - Data sources
21. Nutrition - Interpretation and action
22. Health services
23. Vaccination programmes
24. Water supply, sanitation, and shelter
25. Violence
26. Presentation of results
27. Formulating conclusions and recommendations
28. Dissemination and action

Number of excess deaths

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Many surveys which measure mortality in emergency-affected populations present the number of excess deaths which have occurred since the emergency began. This is hypothetically the number of deaths caused by the emergency itself, or rather the number of deaths that would not have occurred had the emergency not happened.

Calculation of excess deaths requires a baseline, pre-emergency mortality rate, which is often difficult to obtain. The difference between this baseline and the mortality rate found in the survey is then multiplied by the population size to obtain the number of excess deaths. The number of excess deaths is heavily dependent on what pre-emergency mortality is assumed and on the estimated population size.

1

In a population of 10 million people, a survey was done to measure mortality since an emergency began one year ago. The pre-emergency baseline crude mortality rate was 6 deaths per 1000 per year. The crude mortality rate estimated from the survey for the past year was 8 deaths per 1000 per year. How many excess deaths have occurred since the emergency began one year ago? a) 5000 b) 1000 c) 500,000 d) None e) 20,000 Correct. For each 1000 persons in the population, an extra 2 deaths occurred since the emergency began a year ago: 2 x (10 million divided by 1000) = 20,000. Incorrect. Think of it this way: For each 1000 persons in the population, an extra 2 deaths occurred since the emergency began a year ago: 2 x (10 million / 1000) = 20,000. Your answer has been saved.

For a much more complete discussion of this and other issues in measuring mortality rates, see Checchi F and Roberts L. Interpreting and using mortality data in humanitarian emergencies: a primer for non-epidemiologists. Humanitarian Practice Network No. 25. Overseas Development Institute, 2005. (Click here to open this docuent.)