Measles

Measles is an acute infection caused by measles virus. It spreads chiefly through the air when an infected person breathes, coughs, or sneezes. The virus can remain infectious in the air or on contaminated surfaces for up to about two hours, so transmission can occur after the infected person has left a space. An infected person can transmit measles from four days before the rash appears until four days afterward. Because the disease spreads readily among people without immunity, cases can lead to outbreaks when vaccination coverage is insufficient.

Symptoms typically begin about 7–14 days after exposure. Early signs include fever, cough, a runny nose, and red, watery eyes. Small white spots, known as Koplik spots, may appear inside the cheeks. A red rash usually follows several days later, beginning on the face or hairline and spreading down the body. The rash is a characteristic sign, but the illness can be serious beyond its visible skin symptoms.

Many people recover, but measles can cause complications including ear infections, severe diarrhoea and dehydration, pneumonia, and encephalitis, which is inflammation of the brain. Severe outcomes are more likely among children under five, people with malnutrition or weakened immune systems, and pregnant people. Measles infection can also impair immune protection against other infections for a period after recovery. There is no specific antiviral treatment for measles; medical care focuses on supportive care and managing complications.

Vaccination is the most effective way to prevent measles and reduce the risk of outbreaks. The measles vaccine is often given in combination with vaccines against mumps and rubella, as the MMR vaccine. Two doses are recommended in routine immunization programmes because one dose does not produce immunity in every recipient; the schedule varies by country. Public health programmes combine vaccination with case detection, laboratory surveillance, and outbreak response. The World Health Organization estimates that measles vaccination prevented nearly 59 million deaths worldwide between 2000 and 2024, while noting that gaps in coverage allow outbreaks to recur.