An outbreak of scarlet fever has hit record levels, with about 600 new cases a week across England, public health chiefs warned today.

The highly contagious disease typically affects children aged about four, with 90 per cent of cases being in those under 10.

Public Health England issued the alert today as it confirmed 6,157 new cases since last September, a 24 per cent increase on the same period last year, and more than double the figure two years ago.

In London there has been a 30 per cent rise, from 454 to 593 cases. Numbers are expected to soar as it moves towards the traditional Easter peak.

GPs were put on alert and urged to treat infections with antibiotics as speedily as possible. Parents were advised not to delay seeking additional medical help if symptoms did not clear up within a few days.

Dr Theresa Lamagni, PHE’s head of streptococcal infection surveillance, said: “Parents can play a key role in recognising when their child needs to be seen by their GP.

“Early signs to look out for are sore throat, headache and fever with the characteristic pinkish/red sandpapery rash appearing within a day or two, typically on the chest and stomach but then spreading to other parts of the body.

“Individuals who think they or their child may have scarlet fever should seek advice from their GP without delay as prompt antibiotic treatment is needed.”

There has been a slight increase in the most serious group A streptococcal strain, which can lead to ear infection, throat abscesses and pneumonia.

Scarlet fever is spread through close contact with individuals carrying the organism (often in the throat) or indirect contact with objects and surfaces contaminated with the bacterium that causes scarlet fever.

Unusually high numbers of scarlet fever cases were noted in 2014, the highest since 1969. These continued last year and rose again this year.

PHE said symptoms usually clear up after a week and the majority of cases will resolve without complication as long as the recommended course of antibiotics is completed.

Children with scarlet fever – for which there is no vaccine – should stay off school for at least 24 hours after starting antibiotics.