Tuesday, 21 May 2013

What is Measles and Why is there an Outbreak in the UK?

Measles has been in the news a lot lately. It's usually rare in developed countries but may be common in developing ones. However, last year nearly 2,000 cases were recorded in the UK, which was a record at that time. More than 1,200 cases have already been diagnosed this year. Generally only a few dozen cases appear each year in the UK.

The Measles Vaccine

A child with measles
Barbara Rice and the CDC, public domain image
The increase in the incidence of measles is blamed on a 1998 report in which a doctor claimed that the MMR vaccine (for measles, mumps and rubella) was linked to the development of autism. Many parents refused to get their children vaccinated based on this report. The report was heavily criticized and was eventually discredited. The doctor was accused of dishonesty and was prohibited from practicing medicine in the UK, but by then the damage had been done. The public's belief that the vaccine was dangerous persisted.

There is now a large pool of children and teenagers who have never been vaccinated against measles (although vaccination is increasing during the present disease outbreak). These people have a high probability of developing measles and of infecting other people.

How is the Virus Spread?

The measles virus is very infective. It's spread in liquid droplets released by the nose and mouth as a person breathes, talks, coughs or sneezes. When unvaccinated people live in the same house as an infected person, there is a ninety percent probability that the healthy people will become infected too.

Symptoms of Measles

For one to two weeks after the initial infection there are no symptoms. This is known as the incubation period. Then symptoms such as a cough, a runny nose, red eyes and a fever appear. There may also be sensitivity to light. The affected person may at first appear to have a cold or the flu. About two days after the symptoms appear, red spots may be seen inside the cheeks. The spots often have blue-white centers and are known as Koplik or Koplik's spots. About two days later a skin rash made of red or red-brown blotches appears. The rash first appears on the forehead, behind the ears or on the face. Then it spreads downwards, eventually covering the body. The affected person can pass the disease to another person from about four days before the rash appears until about four days after it first appears.

Possible Complications

Most people recover from measles. Some people experience complications, however, which may be serious. These complications include pneumonia, croup and otitis media (a middle ear infection). In some cases a dangerous inflammation of the brain called encephalitis develops. The effects of measles are generally more severe in adults than in children.

Protecting the Population

Experts say that more than 90% of a population needs to be vaccinated to prevent a measles outbreak. In some parts of the UK the vaccination rate amongst people aged ten to sixteen is less than 50%, according to an Associated Press report. The worst hit area is Wales. Vaccination clinics are being held, but it isn't compulsory for parents to get their children immunized. Some children have been hospitalized during the current outbreak, and one adult with measles has died. It's not known if the the measles infection caused the death, however.