Strep A: What are the symptoms and how infectious is it?

Strep A is a common bacterial infection which causes strep throat, tonsillitis and scarlet fever and it is easily treatable with antibiotics. Penicillin is the preferred medication of choice in the UK. But while it is a common infection it can also, in rare cases, lead to a severe condition called invasive Group A Strep (iGAS).

For the vast majority of Strep A infections, the condition is easily treated with a course of antibiotics – but the disease does have the ability to rapidly escalate, leading to scarlet fever and iGAS.

Most sore throats are caused by a virus and will resolve naturally in children and antibiotics will be futile. But experts say that if the sore throat gets worse, it may be Strep A. Parents should keep an eye on their child’s condition for signs of deterioration, with symptoms such as a peculiar, bumpy red rash and a so-called “strawberry tongue”, where the tongue develops a white coating which peels off and exposes a bright red and swollen tongue covered in little bumps.

“Sometimes [Strep A] causes scarlet fever, which is the most common thing that people might have heard of,” says Dr Liz Whittaker, a consultant in paediatric infectious diseases at Imperial College healthcare. “That’s when they get a sore throat, a red tongue and red face and a red rash that feels rough. That should always be treated with some antibiotics.

“Scarlet fever cases have been increasing in the UK, unsurprisingly, across the last six months. What we’ve seen recently in the last few weeks is an increase in the more severe end of the spectrum of invasive Group A Strep (iGAS).” She tells the Telegraph that in severe cases this can manifest as shock, sepsis, pneumonia and, in extremely rare cases, meningitis.

Official statistics from the UK Health Security Agency show that for every 100,000 cases of scarlet fever, 3.1 people will develop iGAS. However, the rate is around nine per 100,000 for children less than one year old and eight for children aged one to four.

Data show the rate of iGAS is higher this year than it was pre-pandemic for children aged between one and nine years old. There have been almost 16,000 cases of scarlet fever in England in the last 12 months and 1,766 cases of iGAS.

Dr Whittaker adds that doctors and A&E workers, as well as parents, should be on the lookout for children with an unusual red rash “because there is a strain circulating at the moment and a slight increase in incidence in some children”, adding: “It’s still rare but is increasing, as might be expected in a group of children who haven’t seen it for two years.”

An individual’s risk from the bacteria is the same as pre-pandemic, she says, but their exposure is higher now due to it circulating freely for the first time in several years.

A senior health expert in the Government told The Telegraph: “Now that everything’s going back to normal we are going to see these cases coming back just like we did before the pandemic. There may be a few more cases now than there would have been before [Covid] because all these children didn’t get any infection during the pandemic and therefore there are more kids around who haven’t had it.

“If this had been spread over three years it may not be as high at all but because they're all getting it together it looks like there's a lot more infections.”

Health authorities issued guidance recently saying that children who recently had flu or chickenpox are more likely to develop a serious case, such as iGAS, if they catch Strep A. Chickenpox causes lesions which allows the bacteria to get into the bloodstream and this makes it easier for the invasive form of the disease to occur.

For flu, the viral infection damages the respiratory system and changes the immune system, which makes it easier for the bacteria to spread into deeper areas and cause more harm. Dr Whittaker says if a child has had chickenpox or the flu one or two weeks prior to catching strep A, they are at a slightly higher risk of severe disease due to weakened immune defences.

“With most viral infections you'll have a fever for up to five days and then often it’ll settle,” she says. “If you suddenly start getting high fevers again a couple of days later then that’s possibly a secondary bacterial infection.” She adds that if a child gets a fever again more than a week after recovering from the initial bout of sickness then that is something for parents to keep an eye on to seek medical advice.

Flu is on the rise in the UK with hospitalisation rates on the rise in children and the elderly.

Scientists this week announced that a superbug strain of Strep A has been discovered which is undetectable and immune to some antibiotics, but not penicillin. Researchers from Australia found Strep A has evolved a new way to nullify some antibiotics and this type of antimicrobial resistance (AMR) is undetectable with current science.

“This new form of resistance is undetectable under conditions routinely used in pathology laboratories, making it very hard for clinicians to prescribe antibiotics that will effectively treat the infection – potentially leading to very poor outcomes and even premature death,” says Dr Timothy Barnett, study author and head of the Strep A pathogenesis and diagnostics team at the University of Western Australia who discovered the strain.

In Britain, Strep A is most commonly treated with penicillin which is not affected by this new form of resistance. Trimethoprim and sulfamethoxazole are the antibiotics which are circumnavigated by this new form of AMR.

Health authorities in the UK say they regularly check whether cases of bacterial infections are resistant to any treatments and there is no reason to believe the current outbreak in Surrey is the new superbug strain of Strep A.