General information, not a diagnosis Method and limitations

Fact sheetVirus

Measles

Measles is highly contagious by air. The eruption is not enough to confirm the diagnosis.

Documentary Enrichment: · General information

Essentials

Very contagious viral disease that can cause serious complications, especially in young unimmunized children.

Agent
Measles virus
Transmission or exposure
Respiratory

Situation and vulnerability

Unvaccinated children and pregnant or immunocompromised people may experience significant complications.

Signs and limits of their interpretation

Measles can start with fever, cough, runny nose and red eyes before rash. The eruption is not necessarily the first sign. Respiratory, digestive or neurological complications may occur, particularly in unimmunized individuals.

Diagnosis and monitoring

A suspicion must be reported to the professional before going to the waiting room to organize the recourse and limit contacts. The confirmation is based on the medical investigations and examinations indicated. Vaccine evidence and contact history help the assessment.

Check these benchmarks in the WHO reference →

Prevention and care

Prevention is based on vaccination according to the applicable schedule. After contact, a professional will quickly assess possible measures.

Practical issues

Do we have to warn you before we consult?

Yes. Report by telephone a suspicion or contact with measles so that the service organizes reception and limits exposures.

Can measles be transmitted before rash?

Yes. WHO describes a possible transmission from four days before and up to four days after its occurrence. Absence of rash does not prevent contact at risk.

Preparing for an exchange with a professional

  • Dates of fever and rash
  • Vaccine diary and documented history of measles
  • Contact with a case, pregnancy or immunosuppression in the surrounding area

Bring the full minutes and dates. This information facilitates evaluation; its collection must not delay an urgent appeal.

Individual decisionThe choice of a test, treatment or prevention depends on the local situation and recommendations. In case of distress, call 911.
An open window in an empty consultation room, natural light and spaced chairs. AI-generated illustration.
Prevention illustration — Rougeole — An open window in an empty consultation room, natural light and spaced chairs.
Image generated by artificial intelligence. AI illustration; it does not depict a disease, biological agent or diagnosis.

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Related fact sheets

These sheets share ways or contexts of exhibition in our catalogue. This reconciliation does not establish a differential diagnosis.

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In practiceObserve and understand

Infectiousness does not start with the rash

According to WHO, an infected person can transmit measles from four days before to four days after the rash begins. Contact tracing must therefore include the days before the rash.

Digitally colourised electron micrograph of measles virus
Measles virus: real electron microscope observation with added colour. CDC / Cynthia S. Goldsmith ; William Bellini, Ph.D. Public domain. Free source, credits and terms: CDC PHIL. A laboratory image cannot interpret personal exposure or establish a diagnosis.
Infectiousness does not start with the rash — explanations and limits
Detail to recordUse in the medical discussionLimit
Onset of the rashReference point for reconstructing contact dates.The first rash date does not establish when infection occurred.
Shared placesMention waiting rooms, school and public transport used, in particular.A list of places alone does not determine who was infected.
Vaccination recordsProvide documented doses and available dates.Professionals assess contacts and any necessary measures.
Keep in mind

If measles is suspected, contact the professional before entering a waiting room so they can arrange your arrival. This timeline is general guidance, not an individual calculation of when infectiousness ends.

References for these explanations

Sources consulted on . Examples and diagrams are educational; the original guidance defines its scope.