The number of cases of the highly contagious scarlet fever has reached a record weekly high, health officials have warned.
Public Health England (PHE) said that t here is a "continued significant increase" in the number of cases in England.
In the last week of March officials were notified of 883 new cases - the highest weekly total since 1982 when weekly records began, a spokeswoman said.
Since September 2013 PHE has noted 5,012 new cases when they would normally only expect to see around 1,400.
"We are continuing to see increases in scarlet fever notifications across England and are working closely with healthcare professionals to try and understand the reasons behind these increases and do our best to reduce the impact of this infection," said PHE's head of streptococcal infection surveillance Dr Theresa Lamagni.
"PHE urges people with symptoms of scarlet fever, which include a sore throat, headache and fever accompanied by a characteristic rash, to consult their GP. Scarlet fever should be treated with antibiotics to reduce risk of complications.
"Once children or adults are diagnosed with scarlet fever we strongly advise them to stay at home until at least 24 hours after the start of antibiotic treatment to avoid passing on the infection."
Scarlet fever is a highly contagious bacterial illness that causes a distinctive pink-red rash which feels like sandpaper to touch.
It can be itchy and start in one area, but soon spreads to many parts of the body, such as the ears, neck and chest.
Other symptoms include a high temperature, vomiting, a flushed face and a red, swollen tongue.
Scarlet fever usually follows a sore throat or skin infection and is most common between the ages of two and eight.
It is caught by breathing in bacteria in airborne droplets from an infected person's coughs and sneezes, or through touching their skin.
Sharing contaminated towels, baths, clothes, bedding, cups and utensils can also pass on the infection.
It is treated by antibiotics which must be taken for 10 days, even though most people recover after four to five days.
There are normally seasonal rises in scarlet fever between December and April each year. Every few years there is also a notable increase in the number of cases and the latest bout of infections is likely to be part of that cycle, experts have said.