Measles is a highly contagious viral infection that spreads easily from an injected person by coughing, sneezing or even just breathing.
Symptoms develop between six and 19 days after infection, and include a runny nose, cough, sore eyes, a fever and a rash.
The rash appears as red and blotchy marks on the hairline that travel down over several days, turning brown and eventually fading.
Some children complain of disliking bright lights or develop white spots with red backgrounds on their tongue.
In one in 15 cases, measles can cause life-threatening complications including pneumonia, convulsions and encephalitis.
Dr Ava Easton, chief executive of the Encephalitis Society told MailOnline: ‘Measles can be very serious.
‘[It] can cause encephalitis which is inflammation of the brain.
‘Encephalitis can result in death or disability.’
Treatment focuses on staying hydrated, resting and taking painkillers, if necessary.
Measles can be prevented by receiving two vaccinations, the first at 13 months old and the second at three years and four months to five years old.
Source: Great Ormond Street Hospital