Measles
Measles is an acute, highly infectious viral illness caused by the measles virus (morbillivirus, family Paramyxoviridae). It produces a characteristic prodrome of fever with cough, coryza and conjunctivitis, a pathognomonic enanthem (Koplik spots) and a cephalocaudally spreading maculopapular rash.
Because of its transmissibility and the availability of effective post‑exposure interventions, any suspected case requires prompt isolation, laboratory confirmation and urgent public‑health action. (Green Book; UKHSA)
Aetiology and transmission
- Agent: measles virus (morbillivirus, Paramyxoviridae). (Green Book)
- Transmission: predominantly airborne and droplet spread from respiratory secretions; highly contagious. Infectious aerosols can persist in enclosed spaces and infect people beyond immediate close contacts. (Green Book; UKHSA)
Incubation and infectious period
- Incubation period: typically about 10 days (range approximately 7-18 days). (Green Book)
- Infectious period: from about 4 days before rash onset to about 4 days after rash appears; use these intervals for exclusion and contact management. (Green Book; UKHSA)
Clinical features
Prodrome
- Typical prodrome: high fever with the triad of cough, coryza and conjunctivitis. Generalised malaise, anorexia and irritability are common. The prodrome usually lasts 2-4 days before the rash. (Green Book)