What is measles?
Measles is a highly contagious disease caused by morbillivirus. Initially the symptoms are like the common cold with fever, conjunctivitis (sore red eyes), cough, and characteristic Koplik spots (small white spots in the mouth). Between days 3 to 7 of the illness a red blotchy rash appears on the face that then becomes more generalised.
Measles is also known as English measles, rubeola and morbilli.
How common is measles?
Before widespread immunisation against measles in industrialised countries, measles was a very common childhood disease that carried a high death rate. Nowadays in countries where measles is part of an immunisation programme, the risk of exposure and incidence of actual disease cases is low. However, because of a recent trend by some parents not to immunise their children, the number of cases of measles, and its complications, is once again increasing.
In developing countries, measles still occurs frequently and is associated with a high rate of complications and death. It remains a common disease even in some developed countries of Europe and Asia. Measles still causes more than a million childhood deaths each year.
How do you get measles?
Measles is highly contagious and is easily spread from person to person by breathing in airborne respiratory droplets from an infected person's coughing or sneezing. An infected person is contagious from 2 days before any symptoms show to at least 5 days after the onset of rash.
An acute infection of measles almost always gives lifelong immunity.
Who is at risk of measles?
Groups of individuals who are at greater risk of measles infection include:
- Infants who have lost their passive immunity from their mothers (acquired from their mother through transfer of antibody across the placenta) and before their first immunisation
- Unvaccinated travellers to areas where measles is endemic (common)
- Individuals with immunodeficiency (e.g. due to infection with HIV/AIDS, leukaemia, cancer, corticosteroid therapy), regardless of their immunisation status
- Migrants and refugees
Individuals at greater risk for severe measles and its complications include:
- Malnourished individuals (particularly vitamin A deficient)
- Those with an underlying immune deficiency
- Pregnant women
What are the signs and symptoms of measles?
Measles appears as distinct clinical stages.
How is measles diagnosed?
Diagnosis of measles is based on the characteristic history and physical examination. Because the disease is now so rarely seen in developed countries, any suspected cases require laboratory confirmation. This is particularly useful in the following situations:
- Sporadic cases
- Atypical cases
- Confusion with other diseases
The usual way to diagnose acute measles is using a viral nasopharyngeal swab and throat swab for polymerase chain reaction (PCR). This needs to be done within 7 days of onset of rash. Blood is taken for measles IgM and IgG antibodies; this test can also be done after recovery from the illness.
What is the treatment of measles?
There is no specific treatment for measles which is why immunisation is so important. Treatment for mild cases of measles is supportive.
- Give paracetamol for fever
- Maintain fluid intake so dehydration doesn't occur
- Provide nutritional support if necessary
- Observe high-risk individuals carefully to prevent complications
Severe cases of measles usually require hospitalisation. Antibiotics may be given to treat secondary bacterial infections from complications such as otitis media, infectious diarrhoea, pneumonia and sepsis.
What are the complications from measles?
Approximately 30% of reported measles cases have one or more complications. The most common complications that occur are:
- Diarrhoea that may be fatal if dehydration occurs
- Otitis media (almost exclusively in children) which may lead to deafness
- Pneumonia (either primary viral or secondary bacterial). This is the most common cause of death.
Other complications include bronchitis, croup, conjunctivitis and/or corneal ulceration leading to blindness (especially if vitamin A deficient), mouth ulceration, acute glomerulonephritis (inflammation of kidneys), acute renal failure and malnutrition (especially if from poor community).
Measles infection during pregnancy increases the risk of premature labour and delivery, and fetal loss. There is also a risk of maternal death.
How to prevent measles
Measles can be prevented by vaccination with live attenuated measles vaccine. It is available as a single antigen preparation or combined with live attenuated mumps or rubella vaccines, or both. Combined measles, mumps and rubella (MMR) vaccine is currently part of routine immunisation programmes in most industrialised countries, including New Zealand.
Measles vaccine induces long-term (probably life-long) immunity in most individuals. Vaccination schedules recommend a two-dose immunisation strategy, the first dose at 12-15 months, followed by a second dose at 4-6 years. Individuals vaccinated prior to 1968 may require revaccination as vaccines used before this time may not have conferred life-long immunity.