Scarlet fever is at its most prevalent for almost 50 years, official figures show.
There were 17,586 cases last year, the largest annual total since 1967, according to Public Health England.
The disease is most common in children under ten. It causes a sore throat, fever and rash which can occasionally lead to pneumonia.
Scarlet fever was very common in the Victorian era but cases dramatically reduced during the last century, partly due to better hygiene.
Health officials are unclear as to why it has suddenly returned and blame 'long-term natural cycles'.
But researchers in the US, where cases are also on the rise, have linked it to a super-resistant and aggressive strain of the bacteria called streptococcus. GPs and parents are being urged to be extra vigilant for symptoms, particularly in young children. In very rare cases it can cause complications with the kidneys and heart.
Dr Theresa Lamagni, Public Health England's head of streptococcal infection surveillance, 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.
'Potential complications include ear infection, throat abscess and pneumonia. Patients who do not show signs of improvement within a few days of starting treatment should seek urgent medical advice.'
Experts say the disease was far more deadly in the Victorian era as it was caused by a different strain of bacteria, which was later eradicated. During the period there were around 100,000 cases a year and up to 20,000 deaths. Dr Lamagni added: 'There's no suggestion what we are seeing now is anything like during the Victorian era. Scarlet fever itself isn't serious. We are not worried in the sense that we are likely to see a lot of problems - but it is of concern because this bacteria can be nasty for some people.'
She advised parents to look out for a rash, usually starting on the back, a temperature and the child complaining of headache and nausea.
'Look out for symptoms and if the child has got these symptoms, go and see your GP,' she said. 'If you are given antibiotics, make sure you finish them.'
The figures from Public Health England show that 17,586 cases were reported in England in 2015, compared with only 1,678 in 2005. Officials expect the number to rise further over coming weeks as the bacteria is most active during March and April.
The disease is caused by the bacteria group A streptococcus and is spread through coughs and sneezes or touching contaminated objects.
In most cases it clears up by itself but GPs may prescribe penicillin if symptoms are particularly nasty or there is a risk of complications.
American researchers have suggested the sudden resurgence is due to a mutant strain of group A streptococcus which is particularly aggressive and spreads very quickly.
But Public Health England said it had ruled out this theory and rigorous lab testing had not found any evidence to support it.
Scarlet fever usually develops after a sore throat or a skin infection caused by the same bacteria.
The NHS advises anyone with the condition to stay at home for 24 hours after starting treatment as they may still be infectious.
Schools affected by outbreaks have been carrying out deep cleans and installing disinfectant dispensers in corridors.
- Daily Mail