Childhood illnesses - Measles

Useful information on the symptoms, diagnosis, treatment and complications of measles, plus advice on the measles vaccine.

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Measles, also known as rubeola, is a common disease caused by a virus of the genus Morbillivirus. It is highly infectious and used to be the commonest childhood disease.

Reports of measles go back to at least 700, however, the first scientific description of the disease and its distinction from smallpox is attributed to the Muslim physician Ibn Razi (Rhazes) 860-932 who published a book entitled Smallpox and Measles. In 1954, the virus causing the disease was isolated, and licensed vaccines to prevent the disease became available in 1963.

Measles is spread through respiration (contact with fluids from an infected person's nose and mouth, either directly or through aerosol transmission), and is highly contagious. 90% of people without immunity sharing a house with an infected person will catch it. Airborne precautions should be taken for all suspected cases of measles.

The incubation period usually lasts for 10-12 days (during which there are no symptoms). Infections occurs by droplets from the mouth or nose. It may start like a bad cold with lots of catarrh and a temperature. Infected people remain contagious from the appearance of the first symptoms until 3-5 days after the rash appears.

Symptoms

The classical symptoms of measles include a fever for at least 3 days duration, and the three C's, cough, coryza (runny nose) and conjunctivitis (red eyes). The fever may reach up to 40 degrees Celsius (105 Fahrenheit). Koplik's spots seen inside the mouth are pathognomic (diagnostic) for measles but are not often seen, even in real cases of measles because they are transient and may disappear within a day of arising.

The rash in measles is classically described as a generalised, maculopapular, erythematous rash that begins several days after the fever starts. It starts on the head before spreading to cover most of the body. The measles rash also classically stains by changing colour to dark brown from red before disappearing later. The rash can be itchy.

Diagnosis

A detailed history should be taken including course of the disease so far, vaccination history, contact history and travel history.

Clinical diagnosis of measles requires a history of fever of at least 3 days together with at least one of the three Cs above. Observation of Koplik's spots is also diagnostic of measles. Alternatively, laboratory diagnosis of measles can be done with confirmation of positive measles IgM antibodies or isolation of measles virus from respiratory specimens. Positive contact with other patients known to have measles adds strong epidemiological evidence to the diagnosis.

Treatment

There is no specific treatment for uncomplicated measles. Patients with uncomplicated measles will recover with rest and supportive treatment.

Complications

Complications with measles are relatively common, ranging from relatively common and less serious diarrhea, to bronchitis, ear infections, and croup; to pneumonia and encephalitis (affecting the nervous system). Complications are usually more severe amongst infants and adults who catch the virus.

The fatality rate from measles for otherwise healthy people in developed countries is low: approximately 1 death per thousand cases. In underdeveloped nations with high rates of malnutrition and poor healthcare, fatality rates of 10 percent are common. In immunocompromised patients, the fatality rate is approximately 30 percent.

Public Health

In developed countries, most children are immunised against measles soon after birth as part of a three-part MMR vaccine (measles, mumps, and rubella). Vaccination rates have been high enough to make measles relatively uncommon. Even a single case in a college dorm or similar setting is often met with a local vaccination program, in case any of the people exposed are not already immune. In developing countries, measles remains common.

Measles is a significant infectious disease because, while the rate of complications is not high, the disease itself is so infectious that the sheer number of people who would suffer complications in an outbreak amongst non-immune people would quickly overwhelm available hospital resources. If vaccination rates fall, the number of non-immune persons in the community rises and the risk of an outbreak of measles consequently rises.

According to the World Health Organisation, measles is the leading cause of vaccine preventable childhood mortality - there are 30 million cases and 875,000 deaths caused by measles every year.