Measles cases could reach their highest level for a decade because of parents shunning vaccinations for their children, a Government scientist has warned.
Dr Mary Ramsay, an epidemiologist at the Government's Health Protection Agency, said 60,000 unvaccinated children started school this year, raising fears that the disease could spread easily through classes.
Official figures this week are predicted to show that Britain is heading for a second consecutive year of record measles cases, with children between five and nine hit the hardest.
Measles can cause meningitis, pneumonia, liver infection, inflammation of the brain, bronchitis and a dramatic drop in white blood cells.
A 13-year-old boy died from measles in 2005 and it is feared that if the numbers of cases continue to rise another death is inevitable.
Dr Ramsay said: "I think we are definitely going to have an epidemic at some stage but it is difficult to predict when."
Last year, there were 739 cases of measles. So far this year there have been 644.
Leeds and North London are particular hotspots, with Great Ormond Street Hospital having treated two children in intensive care.
One of those was Lydia Ayirebi, of Potters Bar, Herts, who almost died after contracting measles-related pneumonia at the age of seven months.
For three days she was so weak that she could not breathe for herself. Her mother Annette Ayirebi, 43, said: "One doctor shook his head and said this kind of thing should never be seen in our society. He was clearly moved and angry.
"It really brought it home how dangerous this disease is. We should fear measles much more."
Uptake of the measles, mumps and rubella (MMR) injection plummeted after Dr Andrew Wakefield published research in 1998 linking it to bowel disorders and autism.
Despite widespread condemnation of the research, parental confidence has remained low since, although uptake rates are rising again.
Vaccine coverage needs to be at 90 to 95 per cent for "herd immunity" — where even the unvaccinated are protected because there is so little of the disease circulating in the community.
At its lowest, uptake of the MMR injection was 88 per cent but in some parts of the country, particularly London, rates plunged to just 50 per cent.
Dr Ramsay said it was "no coincidence" that MMR coverage was lowest in London and the city is now having its biggest outbreak of measles for 10 years.