Parents are being warned to look out for signs of scarlet fever in children after the highest number of reported cases since 1982, health official said.
The highly contagious infection mainly affects young children and is not usually serious if treated.
Official figures from Public Health England (PHE) show there were more than 15,500 cases reported in the first three months of the year - twice as many as last year.
There were 1,624 cases in the most recent week, up to April 1, with a spike of 2,105 cases the week before nationally.
In Yorkshire and Humber, 191 cases of scarlet fever were reported that week, compared to 91 in the same week a year go.
Nick Phin, deputy director of National Infection Service at PHE, said: “While it is not uncommon to see a rise in cases of scarlet fever at this time of year, the numbers we have seen this year have not been seen since 1982 when PHE took over responsibility for collecting data on notifiable diseases.
“It is important to be aware that, with treatment, scarlet fever is not usually a serious illness.”
The latest Health Protection Report also showed 11,982 cases of scarlet fever were reported from mid-September to March, compared to an average of 4,480 for the same period over the last five years.
The first signs of scarlet fever can be flu-like symptoms, including a high temperature of 38C or above and swollen neck glands.
A rash, which looks like sunburn and feels like sandpaper, usually appears a few days later.
Those with symptoms should contact their GP, as early treatment with antibiotics can help reduce the risk of complications such as pneumonia and the spread of the infection.
Children or adults diagnosed with scarlet fever are advised to stay at home until at least 24 hours after the start of antibiotic treatment.
Dr Renu Bindra, of Public Health England Yorkshire and Humber, said: Scarlet fever is not usually a serious illness and can be treated with antibiotics to reduce the risk of complications and spread to others.
“We are monitoring the situation closely and remind parents to be aware of the symptoms of scarlet fever and to contact their GP for assessment if they think their child might have it.
“Whilst there has been a notable increase in scarlet fever cases when compared to last season, greater awareness and improved reporting practices may have contributed to this increase.”