1. Investigation and Response
Disease Outbreak
Investigation and Response
Tom Handzel IERHB, CDC Thanks to Brad Woodruff

2. What are the leading causes of death among children under 5?
Participants should know this – ask for the top killers

3. Leading Causes of Childhood Deaths
Source: WHO estimates of the causes of death in children, Bryce, Lancet, 26 March 2005

4. Where do 10 million children die each year?
The size of the pie is proportional to the number of deaths. The African and South Asian regions account for 70% of worldwide deaths annually among children <5 years. Notice that the sizes of the wedges are relatively constant in the highest mortality regions.
Be sure to focus on the region where this is being presented.
WHO estimates of the causes of death in children, Lancet, 2005

5. What are the major causes of under 5 deaths in emergency settings?
Ask participants to name the leading causes of death in emergency settings.

6. Major Causes of Death in Emergencies for <5 Years
Somalia: Gedo Region 7 Camps, January, 1980
Sudan: Wad Kowli Camp
February, 1985
Measles
ARI
Malaria
Diarrhea
Other
Compare causes of death with previous figures – stressing the importance of these top 4 communicable diseases in emergencies, setting the scene for the proceeding sessions on Measles, Diarrheal diseases, Malaria, Pneumonia and Meningitis.
Source: Centers for Disease Control and Prevention, Famine-Affected, Refugee, and Displaced Populations: Recommendations for Public Health Issues. MMWR, 1992;41(No. RR-13):8.

7. Examples of Recent Outbreaks
Cholera – Kenya, South Sudan
Measles – Aceh, South Sudan, Kenya
Yellow fever – South Sudan
Meningitis – Darfur
Hepatitis E – Darfur
Dysentery – Liberia
Malaria – Ethiopia, Uganda

8. Outbreak Investigations
Why investigate an outbreak?
When to investigate?
How to investigate?

9. Why investigate an outbreak ?
Public Health rational
To design control and preventive measures
To reduce morbidity
To reduce or prevent mortality
Delayed or improper interventions = DEATHS

10. Investigation allows us to (1):
Identify the causative agent
New pathogen causing new disease, e.g. HIV
Old pathogen causing this outbreak (e.g. Hep E, salmonella)
Toxic substances (e.g. insecticides, heavy metals, etc.)
Identify modes of transmission
Design effective and efficient interventions
Identify who is at risk
Geographic location
Age or sex group
Occupation
Other

11. Investigation allows to (2):
Evaluate health services (e.g., vaccine efficacy)
Evaluate public health interventions
Evaluate the surveillance system
Sensitivity, specificity etc.
Contribute to medical knowledge
Communicate and advocate
TAKE ACTION: disease control and prevention

12. Investigation requires:
Basic medical & public health knowledge
Basic concepts of epidemiology
Sources of specialized information (e.g. reference books & specialists)
Knowledge of the environment
Laboratory testing (but not always)
COMMON SENSE !

13. But before investigating an outbreak…
PREPARE for an outbreak if it is likely!!

14. Steps in Investigating an Outbreak
What are the steps in investigating an outbreak?

15. Steps in Investigating an Outbreak (1)
Establish the existence of an outbreak
Confirm the diagnosis
Define a case and count cases
Perform descriptive epidemiology (person, place and time)
Determine who is at risk
Develop hypotheses explaining exposure & disease

16. Steps in Investigating an Outbreak (2)
Evaluate hypotheses
As necessary, reconsider/refine hypotheses and execute additional studies
additional epidemiologic studies
other types of studies – laboratory, environmental
Communicate findings
written report
presentations
Implement control and prevention measures

17. Confirm the Existence of an Outbreak
Definition of outbreak
One case – for diseases of epidemic potential (e.g., measles, cholera)
More than the expected number of cases – for endemic diseases
Sometimes is quantitative threshold (e.g.meningococcal meningitis)
Importance of a good surveillance system for early warning

18. Substantial Rise in Malaria Cases
Monthly malaria admissions and rainfall, Wajir, 50
100
150
200
250
300
350
400
450
500
J96 F M A J S O N D
J97
J98
Malaria admissions
Rainfall

19. Weekly incidence of meningitis, MSF/MOH/Epicentre, Mali, 19975 10 15 20 25 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19
# cases/10,000/day

20. Confirm the Diagnosis Talk with health workers
Examine cases yourself !
Laboratory testing (e.g., malaria, cholera, hemorrhagic fevers, etc.)
Exaggeration of reported outbreaks is common

21. Develop a Case Definition
Must be easily applied by health workers
Preferably does not require laboratory results
Short time with each patient
Must be standardized
Should be relatively sensitive
Detect most cases
May pick up false positives

22. Develop a Case Definition
Measles: 3 possible case definitions
Fever and runny nose?
Fever and rash and Koplik’s spots and conjunctivitis?
CDC case definition: generalized maculopapular rash > 3 days and fever and at least one of the following: cough, coryza or conjunctivitis?

23. Develop a Case Definition
Measles: 3 definitions
Fever and runny nose
Too sensitive
Too many other illnesses produce same symptoms
Call many illnesses “measles”
Fever and rash and Koplik’s spots and conjunctivitis
Too specific
Many cases of measles do not have all these signs
Miss many real cases of measles
CDC case definition: generalized maculopapular rash > 3 days and fever and at least one of the following: cough, coryza or conjunctivitis

24. Develop a Case Definition
Sometimes define levels of certainty regarding diagnosis; for example, meningitis or Ebola
Confirmed case: laboratory confirmed
Probable case: fits all components of clinical case definition
Possible case: suggestive clinical signs but not fit case definition

25. Once Case Definition is Established
Count cases !
Reinforce passive surveillance
Active case finding
You do not have to count all cases, but
What proportion should be detected?
Depends on what you do with data

26. Descriptive Epidemiology
TIME, PLACE, PERSON
May be possible to answer:
Who is at risk?
What is source of infection?
What is mode of transmission?

27. Descriptive Epidemiology - Time
Distribution of cases by date of onset
X axis: time Y axis: number of cases
Shows:
Time limits / duration of the outbreak
Peak / incubation period
Form of curve: evolution of outbreak
Formulate hypothesis regarding source

28. Epidemiologic Curve

29. Epidemiologic Curve

30. Epidemiologic Curve

31. Descriptive Epidemiology - Person
Numerators
Describe cases in terms of
age, sex,
other parameters : refugee / displaced / residents
immunized , not immunized
Denominators
Distribution in the overall population (age, sex,...)
Compare rates to identify high risk groups

32. Descriptive Epidemiology - Place
Map cases: identify geographic places at risk
Determine where disease acquired: Home, work, travel, etc..

33. John Snow’s Map of Cholera Cases

34. Ebola epidemic, Yambuku, Zaire 1976
Yasoku 0.2
Ebola epidemic, Yambuku, Zaire 1976
Yambala 0.1
Yambala 0.7
Yapiki 0.7
Yambuku 4.5
Yamolembia 2.6
Yamisole 2.7
Yaeto-Liku 1.3
Yalosemba 1.0
Badjoki 1.8
Bongola 1.6
Modjambole 0.8
Kokoko 0.8

35. Information to Collect on Cases
Personal information
Age
Sex
Place of residence (address)
Other relevant “exposures”
Refugees vs locals
Food source
Water source
Ethnicity, religion, etc.

36. Information to Collect on Cases
Disease data
Date of onset of symptoms
Clinical symptoms and signs
Immunized or not (measles, meningitis)
Laboratory results (if any)
Duration of disease, outcome (death, cured,..)
Treatment received

37. Develop Hypotheses Often obvious from descriptive epidemiology
Formulate idea about source of outbreak and mode of transmission

38. Test Hypotheses Cross – sectional study? Cohort study
Case – control study
Identify cases
Select control group
Possibly matched on age or sex or location
Community control, clinic control etc.
Compare exposures among cases and controls
Calculate odds for various exposures

39. Write a Report Clarifies your own ideas / synthesis
Presents data and conclusions to anyone interested
Often epidemiologist don’t implement interventions
Must communicate to those who will intervene
Advocacy: MOH, UN, other NGOs, donors
Basis for future reference

40. Implement - Take ACTION
Interventions include
Prevention of further cases
Control of transmission and source of infection
Improve case management, lower case-fatality rate

41. What would SAVE’s role be in responding to an outbreak?
Outbreak of acute watery diarrhea confirmed as cholera?
Large cluster of measles cases in displaced persons camp?
Sharp increase in measles cases in which SAVE is supporting clinical services ?

42. What preventive measures can be taken to reduce likelihood of an outbreak?
Measles?
Cholera?
Dysentery?
Meningitis?
Malaria?

43. Exercise
SAVE supports clinical services in a large IDP camp with 75,000 persons. A large number of cases of acute jaundice syndrome is detected and local physicians suspect hepatitis. Your clinicians report several deaths among adult women.
What would you do to investigate or confirm this?

44. Exercise – part 2
Laboratory confirms agent is Hepatitis E. Over 1000 cases have been reported at your clinics. You suspect there are more cases in the camp that have not come to the clinic.
What other epidemiologic information would you like to see? What environmental information?
What would you do about those not coming to the clinics?

45. What do you recommend on the prevention side?
Exercise part 3
An active case search is conducted and more than 3500 cases are detected. Water sources include water from distribution system (sometimes chlorinated), hand pumps. Some persons collect water from streambeds. There are approximately 100 latrines in the camp.
What do you recommend on the prevention side?

46. Example part 4 Steps Taken Chlorination of all water sources (week 32)
Latrine construction
Hygiene promotion and soap distribution
Active surveillance