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Measles Outbreak Investigation Steps for Public Health Response

Understand the steps involved in investigating a measles outbreak to control its spread and prevent further cases. From preparing for fieldwork to establishing case definitions, verifying diagnoses, and implementing control measures.

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Measles Outbreak Investigation Steps for Public Health Response

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  1. Measles Outbreak Danae Bixler, MD, MPH

  2. WVDHHR / BPH / OEHP / DSDC / IDEP

  3. Steps of an Outbreak Investigation • Prepare for fieldwork. • Establish the existence of an outbreak. • Verify the diagnosis. WVDHHR / BPH / OEHP / DSDC / IDEP

  4. Steps of an Outbreak Investigation 4. Define and identify cases. • Establish a case definition • Identify and count cases • Perform descriptive epidemiology. • Develop hypotheses. • Evaluate hypotheses. WVDHHR / BPH / OEHP / DSDC / IDEP

  5. Steps of an Outbreak Investigation (2) 8. As necessary, reconsider, refine hypotheses and execute additional studies • Additional epidemiological studies • Other types of studies – laboratory, environmental • Implement control and prevention measures. • Communicate findings. WVDHHR / BPH / OEHP / DSDC / IDEP

  6. WVDHHR / BPH / OEHP / DSDC / IDEP

  7. Step 1. • Prepare for Fieldwork • Accumulate knowledge, equipment, sample questionnaires, etc. • Anticipate employee health issues • Make travel and leave arrangements • Know your role in the investigation WVDHHR / BPH / OEHP / DSDC / IDEP

  8. Employee Health • Interviewers must be immune: • Two doses of measles-containing vaccine one month apart on or after the first birthday; OR • Laboratory evidence or history of prior disease • Birth before 1957 • consider 1 dose MMR if no history of disease or laboratory evidence of immunity WVDHHR / BPH / OEHP / DSDC / IDEP

  9. WVDHHR / BPH / OEHP / DSDC / IDEP

  10. Measles Basics • Clinical WVDHHR / BPH / OEHP / DSDC / IDEP

  11. Measles Basics • Clinical • Prodrome: • Stepwise increase in fever up to 103-105 F • Followed by cough, coryza, conjunctivitis • Koplik’s spots • 1-2 days before rash to 1-2 days after rash • Punctate blue-white spots on red background WVDHHR / BPH / OEHP / DSDC / IDEP

  12. Measles Basics • Clinical(2) • Rash: maculopapular, begins at hairline, progresses downward • Blanch for first 3-4 days • Discrete => confluent • Fades in order of appearance • May desquamate WVDHHR / BPH / OEHP / DSDC / IDEP

  13. Measles Basics • Complications WVDHHR / BPH / OEHP / DSDC / IDEP

  14. Measles Basics • Complications • Diarrhea 8% • Otitis media 7% • Pneumonia 6% • Encephalitis 0.1% • Death 0.2% • Hospitalization 18% WVDHHR / BPH / OEHP / DSDC / IDEP

  15. Measles in Chicago, 1989MMWR, 1990; 39:317 • Cases = 2232 • Hospitalization 755 (33.8%) • Diarrhea 340 (15.2%) • Pneumonia 186 (8.3%) • Otitis media 52 (2.3%) • Encephalitis 1 (0.04%) • Deaths 8 (0.36%) WVDHHR / BPH / OEHP / DSDC / IDEP

  16. Measles Basics • Reservoir • Transmission WVDHHR / BPH / OEHP / DSDC / IDEP

  17. Measles Basics • Reservoir • Humans • Transmission • Person-to-person via droplets • Airborne in closed area for up to 2 hours after a person with measles occupied the area WVDHHR / BPH / OEHP / DSDC / IDEP

  18. Measles Basics • Incubation period WVDHHR / BPH / OEHP / DSDC / IDEP

  19. Measles Basics • Incubation period • Exposure to prodrome: • Average 10-12 days • Exposure to rash: • 7-18 days • Average 14 days WVDHHR / BPH / OEHP / DSDC / IDEP

  20. Measles Basics • Infectious period WVDHHR / BPH / OEHP / DSDC / IDEP

  21. Measles Basics • Infectious period • From 4 days prior to rash onset to 4 days after rash onset WVDHHR / BPH / OEHP / DSDC / IDEP

  22. Measles Basics • Control measures WVDHHR / BPH / OEHP / DSDC / IDEP

  23. Measles Basics • Control measures • Post-exposure vaccination within 72 hours provides protection • MIG for immunosuppressed, pregnant or infants. • In school or daycare: • exclude unless 2 doses of measles vaccine are documented • In health care • Exclude susceptibles from day 5 through day 21 after exposure WVDHHR / BPH / OEHP / DSDC / IDEP

  24. WVDHHR / BPH / OEHP / DSDC / IDEP

  25. Jay S. • 3 year old healthy male • Onset of ‘cold symptoms’ on 3/7/03; RX amoxicillin on 3/8 because of fever = 105 F • Rash onset 3/10/03 • Blood test ‘negative’ for measles WVDHHR / BPH / OEHP / DSDC / IDEP

  26. Jay S WVDHHR / BPH / OEHP / DSDC / IDEP

  27. Anything else you want to know ???????????

  28. Step 2. • Establish the Existence of an Outbreak • Outbreak (epidemic): occurrence of more cases than expected in a given area or among a specific group of people over a particular period of time. • Cluster: aggregation of cases in a given area over a particular period without regard to whether the number is more than expected WVDHHR / BPH / OEHP / DSDC / IDEP

  29. WVDHHR / BPH / OEHP / DSDC / IDEP

  30. WVDHHR / BPH / OEHP / DSDC / IDEP

  31. Is this an outbreak?

  32. Step 2. • Establish the Existence of an Outbreak • For measles: 1 case = outbreak WVDHHR / BPH / OEHP / DSDC / IDEP

  33. Step 3. • Verify the diagnosis • Typical clinical presentation + • Laboratory confirmation: • Isolation of measles virus (e.g., nasopharynx, urine) • Significant rise in measles IgG by any standard serologic assay • Positive serologic test for measles IgM WVDHHR / BPH / OEHP / DSDC / IDEP

  34. What do you want to do now?

  35. Step 4 • Establish a case definition • Identify and count cases WVDHHR / BPH / OEHP / DSDC / IDEP

  36. Establish a Case Definition • Clinical case definition An illness characterized by all of the following: • A generalized maculopapular rash lasting > 3 days • A temperature > 101 F • Cough, coryza or conjunctivitis WVDHHR / BPH / OEHP / DSDC / IDEP

  37. Establish a Case Definition (2) • Laboratory criteria for diagnosis • Positive serologic test for measles immunoglobulin M (IgM) antibody, or • Significant rise in measles antibody level by any standard serologic assay, or • Isolation of measles virus from a clinical specimen WVDHHR / BPH / OEHP / DSDC / IDEP

  38. Establish a Case Definition (3) • Case Classification • Suspected: Febrile illness accompanied by generalized maculopapular rash • Probable: A case that meets the clinical case definition, has noncontributory or no serologic or virologic testing, and is not epidemiologically linked to a confirmed case • Confirmed: A case that is laboratory confirmed or that meets the clinical case definition and is epidemiologically linked to a confirmed case. A laboratory-confirmed case does not need to meet the clinical case definition. WVDHHR / BPH / OEHP / DSDC / IDEP

  39. The report on Jay S. arrives . . . WVDHHR / BPH / OEHP / DSDC / IDEP

  40. Is Jay a case? • 3 year old healthy male • Onset of ‘cold symptoms’ on 3/7/03; RX amoxicillin on 3/8 because of fever = 105 F • Rash onset 3/10/03 • Blood test ‘negative’ for measles WVDHHR / BPH / OEHP / DSDC / IDEP

  41. Is Jay a case? • Case Classification • Suspected: Febrile illness accompanied by generalized maculopapular rash • Probable: A case that meets the clinical case definition, has noncontributory or no serologic or virologic testing, and is not epidemiologically linked to a confirmed case • Confirmed: A case that is laboratory confirmed or that meets the clinical case definition and is epidemiologically linked to a confirmed case. A laboratory-confirmed case does not need to meet the clinical case definition. WVDHHR / BPH / OEHP / DSDC / IDEP

  42. Step 4 • Establish a case definition • Identify and count cases WVDHHR / BPH / OEHP / DSDC / IDEP

  43. What type of surveillance would you like to do? • Active surveillance • Individually phone / visit health care providers to search for additional cases • Enhanced passive surveillance • Disseminate written request for reports of additional cases WVDHHR / BPH / OEHP / DSDC / IDEP

  44. . . . Good surveillance pays off! WVDHHR / BPH / OEHP / DSDC / IDEP

  45. Peter M. • 7 ½ year old home-schooled previously healthy male • Onset of runny nose, cough, fever of 104 on 3/10/03 • Rash began on the forehead 3/13/03; progressed downward, now fading from the face • Measles IgM (+) on 3/14/03 WVDHHR / BPH / OEHP / DSDC / IDEP

  46. Peter M. WVDHHR / BPH / OEHP / DSDC / IDEP

  47. Is Peter M. a case? • Onset of runny nose, cough, fever of 104 on 3/10/03 • Rash began on the forehead 3/13/03; progressed downward, now fading from the face • Measles IgM (+) on 3/14/03 WVDHHR / BPH / OEHP / DSDC / IDEP

  48. . . . Good surveillance really, really pays off! WVDHHR / BPH / OEHP / DSDC / IDEP

  49. Step 5. • Perform Descriptive Epidemiology • Person • Place • Time WVDHHR / BPH / OEHP / DSDC / IDEP

  50. Measles in Chicago, 1989MMWR, 1990; 39:317 • N = 2,232 • Age • Less than 5 1,663 (74.5%) • Less than 1 422 (18.9%) • Race / ethnicity • Black 1,594 (71.4%) • Hispanics 506 (22.7%) WVDHHR / BPH / OEHP / DSDC / IDEP

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