Measles used to be common in childhood illness, During one of the worst measles epidemics in Jan 1959 the British medical Journal described Measles as the most common childhood infection, complications are extremely rare. Since vacines were developed we are told it is a killer disease. Cases in the UK are rising - they are at their highest level for 20 years. The surest way to be immune from measles is to catch it.

Measles is caused by a virus that is spread by droplets. The virus is passed on through direct contact with someone who's infected, for example by touching or kissing them, or through breathing in contaminated air. It's fairly easy to catch if you haven't been vaccinated and come into contact with someone who has the infection, which is why epidemics often occur among schoolchildren.

The infectious period is from four days before the rash to four days after it's appeared. It's most infectious before the rash appears so people tend to spread the virus before they realise they have it. Although people of any age can get measles, it's most common among those aged between one and four.

People at increased risk from measles

• young babies under one year
• People whose immune system is suppressed, for example by cancer or HIV
• malnourished people
• children with vitamin A deficiency
• pregnant women - the infection may cause miscarriage or premature delivery

Who's affected?

All children who have not contracted measles or not been vaccinated can catch measles. Children who have problems with their immune system (particularly with T lymphocytes) may suffer from a more severe illness.

Children in developing countries are more at risk, malnutrition and vitamin A deficiency often impair a child's immunity and their ability to fight the infection.

What are the symptoms?

Symptoms take about ten to 14 days to develop after exposure to the virus (the incubation period). Early symptoms are like a cold, with runny nose, cough, conjunctivitis and fever. A couple of days later tiny white spots surrounded by red (Koplik spots) may develop on the inside mucosa of the cheeks. These are diagnostic of measles but difficult to see.

The measles rash appears a day or two later, starting behind the ears or on the face and spreading down across the body. It's a fine red rash which becomes blotchy and confluent, fades after three to four days and may peel off after a week or so. Abdominal symptoms may include nausea and vomiting, abdominal pain and diarrhoea. Symptoms usually last about 14 days in all and it's recommended that children stay off school for five days after the start of the rash.

The infection isn't usually serious but there's a risk of complications like there is with a vaccine. These include otitis media, pneumonia, hepatitis, conjunctivitis and encephalitis Although rare, Encephalitis, for example, typically develops after about eight days, with headaches, lethargy and irritability, progressing to convulsions. If your child shows any worrying symptoms during measles get urgent medical .

Your doctor may have never seen a case of Measles so the best people to ask for advice initially may be your grandparents who will have contracted measles themselves. Children may be treated at home, they should be encouraged to drink lots of fluids. Measles is a notifiable disease - if you think your child may have it your doctor  can confirm the diagnosis with a simple saliva test and must then let the local health authority know.

The child is infectious from one day before the onset of symptoms until about five days after the start of the rash, so let friends, family and other potential contacts know.

Vaccination against measles

Children in the UK are offered vaccination against measles as part of the MMR vaccine, which is given to them between 12 and 15 months of age (with a booster dose before they start school).There are concerns about possible risks from vaccination, especially with the combined MMR vaccine, after several researchers (including one at the London's Royal Free Hospital) suggested links with autism.