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

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

Leading Causes of Childhood Deaths Source: WHO estimates of the causes of death in children, 2000-03 Bryce, Lancet, 26 March 2005

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

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

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.

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

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

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

Investigation allows us to (1): Identify the causative agent New pathogen causing new disease, e.g. HIV 1984.. 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

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

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 !

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

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

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

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

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

Substantial Rise in Malaria Cases Monthly malaria admissions and rainfall, Wajir,1996-98 50 100 150 200 250 300 350 400 450 500 J96 F M A J S O N D J97 J98 Malaria admissions Rainfall

Weekly incidence of meningitis, MSF/MOH/Epicentre, Mali, 1997 5 10 15 20 25 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 # cases/10,000/day

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

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

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?

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

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

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

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

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

Epidemiologic Curve

Epidemiologic Curve

Epidemiologic Curve

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

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

John Snow’s Map of Cholera Cases

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

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.

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

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

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

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

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

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 ?

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

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?

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?

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?

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