What is scarlet fever?

Scarlet fever is an infectious childhood illness with sore throat, body rash, and fever caused by Streptococcus pyogenes (group A strep, or ‘Strep A’) but easy to treat with antibiotics.

Scarlet fever is a notifiable infection; peaks of scarlet fever occur in the springtime. Rates in England have risen in the last 4 years to levels seen in the early 1960s for reasons no one is sure of.

Do we need to worry about it?

Although scarlet fever is treatable with antibiotics, rates of rarer but more dangerous group A strep infections can also increase when scarlet fever rates are high. Though very rare, these can kill up to a fifth of those affected through devastating effects of sepsis.

Children in a nurseryHow can we stop the spread?

We want to stop transmission of group A Strep in outbreaks of scarlet fever. The main age group affected are nursery and reception age children aged 4-6 years.

To do this, we first need to understand whether- and how- Strep A spreads in nurseries.

Could better hand hygiene or different treatments reduce spread? Better control of Strep A may ultimately reduce risk of rare but more dangerous infections.

Taking swab from a childWhat is the study doing?

We are visiting homes & nurseries with scarlet fever cases, to take swabs from children being treated for scarlet fever, their household contacts, and healthy classmates.

We have launched an online survey of all households in the London area with notified cases of scarlet fever to collect information about treatment and burden of scarlet fever.

We are also conducting experiments to find out which antibiotics are best at preventing transmission and if there are differences between different Strep A strains.

What are the findings so far?

Previous estimates suggested less than 4% of healthy children carry Strep A in their throats. In the nurseries we studied, 40% of healthy classmates carried the same strain of group A strep in the 3 weeks after children in the same class had been diagnosed with scarlet fever.

333 (20%) of 1,703 households contacted took part in the online survey. All cases received appropriate treatment once scarlet fever was diagnosed. Prior contact with other children with both sore throat and scarlet fever was very common (58% and 67%).

Child coughingWhat next?

The results show intense transmission of group A strep among healthy children, even if their classmates with scarlet fever have been properly treated. We now need to see if these healthy carriers can transmit Strep A from their hands or by coughing.

Transmission from child's handsThe survey suggests that most scarlet fever cases arose after contacts with sore throat, which can also be caused by group A Strep, or scarlet fever (or both) in schools and nurseries. Understanding and controlling transmission of the more common milder Strep A infections can help us reduce the rarer, more harmful forms of the disease.  

The research is being done by Imperial College London together with Public Health England and funded by the charity Action Medical Research for children. The investigators are Professor Shiranee Sriskandan (Imperial College London), Dr Rebecca Cordery (Public Health England) and Dr Theresa Lamagni (Public Health England).