Measles in Adults
On this page
Direct answer
Three days of cough, coryza, conjunctivitis and fever followed by a coppery maculopapular rash starting behind the ears and hairline is measles, an airborne RNA paramyxovirus illness. Koplik spots on the buccal mucosa opposite the lower molars appear in the prodrome and are pathognomonic, and infectivity runs from four days before to four days after the rash. Adults suffer more pneumonitis and hospitalisation than children, post-infectious encephalitis occurs in roughly one in a thousand cases, and subacute sclerosing panencephalitis appears years later in about one in a hundred thousand.
What you must remember
- The 3C prodrome — cough, coryza, conjunctivitis with fever for about three days; Koplik spots (grain-of-salt, bluish-white on an erythematous buccal base) confirm the diagnosis a day before the rash.
- Rash: blanching, coppery-red, maculopapular, beginning at the hairline and behind the ears and spreading downwards, fading in order with fine desquamation.
- Infectivity from four days before to four days after the rash; among the most contagious infections known.
- Giant cell (Hecht) pneumonia occurs especially in the immunocompromised and malnourished, who may die without ever developing a rash.
- Encephalitis: acute post-infectious demyelinating illness around day 4-6 with roughly 10-15 per cent mortality, and SSPE 7-10 years later with myoclonus, periodic EEG complexes, high CSF measles antibody, uniformly fatal.
- Vitamin A two doses 24 hours apart reduces mortality in children; adults are managed supportively, watching for otitis media and pneumonia.
- Pregnancy: measles raises preterm birth and fetal loss but is not a classic teratogen, unlike rubella.
- Measles IgM on a single sample confirms acute infection in an unvaccinated person; two documented vaccine doses or prior birth-year criteria define immunity.
A diagnostic pathway walked through
An unvaccinated 24-year-old has six days of illness: three days of red eyes and catarrh, then a rash from face to trunk, plus barking cough and photophobia. Step one anchors the diagnosis — did buccal spots precede the rash, and did the rash spread head to toe over three days? Blinding descent from the hairline with catarrh separates measles from dengue (retro-orbital pain, thrombocytopenia), rubella (mild illness, postauricular nodes, one-day rash) and drug eruption (no prodrome). Step two hunts complications: chest examination for viral or secondary bacterial pneumonia, liver tenderness with transaminitis, common in adults, and otitis media. Step three is public health — isolate for four days after rash onset, notify, and trace susceptible pregnant and immunocompromised contacts for vaccine or immunoglobulin decisions. Step four documents immunity status for the future. The examinable skill is the chain: recognise, exclude mimics, hunt complications, protect contacts.
How the exam frames it
Measles questions camouflage the diagnosis. A stem describing "sandy grains on the buccal mucosa opposite the lower molars" tests Koplik spots; one describing myoclonic jerks with periodic high-amplitude EEG complexes years after childhood infection tests SSPE. The recurring modified-measles trap is the partially immune patient — vaccinated or given immunoglobulin — whose mild short illness may lack Koplik spots, so IgM serology settles it. Examiners also probe the immunocompromised host, where "giant cell pneumonia without a rash" is the single expected answer.
Frequently asked questions
What are Koplik spots and when do they appear?
Bluish-white grain-of-salt spots on an erythematous buccal base opposite the lower molars, appearing one to two days before the rash and fading within two days of its onset; they are pathognomonic.
Which pneumonia is characteristic of measles?
Primary giant cell pneumonia, a direct viral infection with multinucleated giant cells seen chiefly in the immunocompromised and malnourished, who may have no rash; otherwise secondary bacterial pneumonia is commoner.
How does SSPE differ from post-infectious encephalitis?
SSPE appears 7-10 years later with progressive myoclonus, dementia, periodic EEG complexes and high measles antibody in serum and CSF, and is fatal; post-infectious encephalitis occurs within days of the rash as immune-mediated demyelination.
Why is vitamin A given in measles?
Two doses 24 hours apart reduce mortality, probably by restoring depleted retinol stores and supporting epithelial and immune integrity; the benefit is established in children and is standard programme practice.
How long is a measles patient isolated?
Airborne isolation for four days after rash onset in immunocompetent patients, and for the duration of illness in the immunocompromised, who may shed virus for weeks.