Parents are being urged to take their child to a GP if they suspect scarlet fever, after cases rose in some areas of England.
From September to the end of January, more cases have been reported in the West Midlands compared with the same period last year (369 compared with 309), London (386 compared with 336) and the North West (546 compared with 500).
Public Health England (PHE) urged parents to be vigilant, but said other regions of England are experiencing the same or lower levels of scarlet fever than last year.
Scarlet fever is a bacterial illness that mainly affects children and is distinctive due to its pink-red rash. It is highly contagious and should be treated with antibiotics.
A PHE spokeswoman said: "It's not uncommon to see more cases of scarlet fever during winter and spring.
"Although we have seen a small increase in cases this year, scarlet fever is usually a mild illness that can be treated with antibiotics to reduce the risk of further complications and to minimise the risk of its spread to others.
"Scarlet fever's symptoms include a sore throat, headache and fever with a characteristic sandpapery, fine, pinkish or red rash.
"Parents should pay particular attention and if you or your child develops any of these symptoms you should contact your GP for assessment.
"Children or adults diagnosed with scarlet fever are advised to stay at home until at least 24 hours after the start of antibiotic treatment to avoid spreading the infection to others.
"Since September, 3,325 cases of scarlet fever have been reported across England.
Between 300 and 400 cases of scarlet fever are being reported every week.
The highest levels are usually seen in March and April. Over the past two years, the total number of cases reported by the end of April has been on the rise.
Scarlet fever usually occurs in children, mostly between the ages of two and eight.
Nurseries and schools are told to try and curb the spread of the bug through encouraging youngsters and staff to wash their hands.