CDC/CSTE Measles Case Definition
Classifies a febrile rash illness as suspect, probable, or confirmed measles under the CDC and CSTE case definition.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- A febrile illness accompanied by rash
- Yes
- Temperature at or above 101 F (38.3 C)
- Yes
- Generalized maculopapular rash lasting at least three days
- Yes
- Cough, coryza, or conjunctivitis
- Yes
Result: probable measles: 3 of 3 clinical criteria, 0 laboratory results, no epidemiologic link
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Suspect
- Any febrile illness accompanied by rash. That is the whole definition of the tier, and it is enough to isolate and notify on.
- Probable
- The clinical criteria met, with no contributory laboratory testing and no epidemiologic link to a laboratory-confirmed case.
- Confirmed
- An acute febrile rash illness with virus isolation, nucleic acid detection, a positive IgM or IgG seroconversion; or a direct epidemiologic link to a laboratory-confirmed case.
- Clinical criteria
- Absent a more likely diagnosis: a temperature at or above 101 F, a generalized maculopapular rash lasting at least three days, and cough, coryza or conjunctivitis.
- IgM timing
- A negative IgM in the first seventy-two hours after rash onset does not exclude measles. A positive IgM alone is not conclusive where prevalence is low.
- Vaccination
- Does not exclude measles. Only a rash seven to fourteen days after vaccination with vaccine strain identified is a vaccine reaction rather than a case.
What you enter
- A febrile illness accompanied by rash (the whole suspect definition)
- Temperature at or above 101 F (38.3 C) (clinical criterion)
- Generalized maculopapular rash lasting at least three days (clinical criterion)
- Cough, coryza, or conjunctivitis (clinical criterion)
- A more likely diagnosis has been made (defeats the clinical criteria)
- Measles virus isolated, or measles nucleic acid detected (laboratory evidence)
- Positive serologic test for measles IgM (laboratory evidence)
- IgG seroconversion, or a significant rise in measles IgG (laboratory evidence)
The other 2 fields
- Direct epidemiologic link to a laboratory-confirmed case (confirms on its own with a febrile rash illness)
- Rash began 7 to 14 days after vaccination, with vaccine strain identified (a vaccine reaction, not a case)
How this is calculated
Council of State and Territorial Epidemiologists / CDC. Measles (Rubeola) Case Definition. National Notifiable Diseases Surveillance System. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.