Measles can have serious complications. These are more likely in malnourished children. Vitamin A deficiency in particular worsens the course of measles.  The disease also tends to be more severe in infants younger than one year and in any person who is immunosuppressed, for example people with HIV-infection or leukaemia.

The complications that can occur, are as follows:

    • Croup (inflammation of the vocal cords and upper airways) is apparent by difficult and noisy efforts to inhale.

    • Pneumonia can be due purely to the measles virus itself, but is more often because of added infection of the damaged airways and lung surfaces by other viruses or bacteria. Pneumonia becomes evident through rapid, difficult breathing, worsening cough and chest pain.

    • Middle ear infection is very common and is apparent from pain in the ear.

    • Diarrhoea is usually mild but in malnourished children it can be severe and prolonged and further compromise the child’s nutrition.

    • Inflammation of the gut can, very occasionally, lead to appendicitis in measles.

    • Bacterial infection (profuse pus) of inflamed eyes and scarring of the cornea with partial blindness is another risk for malnourished children if the eyes are not attended to early enough.

    • Measles leaves the individual's immune system suppressed for some weeks to months afterward.

    • Another more immediate consequence of the immune dysfunction can be severe herpes ulceration of the mouth.

    • Encephalitis (inflammation of the brain) occurs in about 1/1 000 cases of measles. The complication can develop in mild cases of measles. Encephalitis usually occurs from two to seven days after the start of the rash, when the child should be starting to recover. At least 10 percent of children with measles encephalitis die and some are left with mental retardation, deafness, paralysis or epilepsy. A delayed, fatal form of encephalitis appearing weeks to months after measles can occur in immunocompromised persons.

    • Subacute sclerosing pan-encephalitis (SSPE) is an extremely rare but dreaded condition occurring usually many years after measles. For unknown reasons, the virus persists in a weakened form in the brain of a very small number of people infected with measles, and eventually begins to cause degeneration in areas of the brain. There is a slow downhill progression to death in every case.

    • Very rarely the rash may be dark ("black" measles) due to bleeding into the skin. This severe type of measles has a high fatality.

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