Strep A: what you need to know

Posted on December 6, 2022   by Helge Dorfmueller, Alex McCarthy and Claire Turner

With a notable increase in serious Step A cases in the UK this year and concern over the risk to young children, we asked three expert Microbiology Society members to answer some common questions about Strep A.

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What is Strep A? 

Strep A is a bacterium that is commonly found in the throat or on the skin of humans. Its full name is Streptococcus pyogenes or Group A Streptococcus. People may carry Strep A without knowing it and they do not become ill or harmed. It’s easily transmitted from person to person through coughing, sneezing and close contact.
- Dr Helge Dorfmueller, University of Dundee, UK.

What are diseases caused by Strep A infection, and how severe are they?

Strep A most often causes a throat infection called 'Strep throat' or tonsillitis. The symptoms are often mild (sore and scratchy throat or swollen tonsils) and these infections are commonly treated with antibiotics. Scarlet fever is an illness that can develop in some individuals that have Strep throat. It mainly affects young children – the first symptoms can be flu-like symptoms such as a high-temperature, sore throat, headache, swollen neck glands and a rash on the chest and tummy and the typical ‘strawberry’ tongue. Strep A also causes superficial infections of the skin including cellulitis and Impetigo. On rare occasions, Strep A gets past our immune system barriers to enter tissues or the blood to cause invasive infections, including sepsis, that are serious and can be deadly.
- Dr Alex McCarthy, Imperial College London, UK.

Why are we hearing about Strep A infections now?

We are hearing about Strep A infections because of the recently increased occurrence of severe infections in children, likely associated with the current high levels of scarlet fever in children. If there are very high levels of infections like 'Strep throat' and scarlet fever, then we will begin to see more of the rarer invasive infections too. The UK has actually been experiencing increased levels of scarlet fever since 2014, with the exceptions of 2020-21 where cases dropped during pandemic restrictions. This year is unusual in that infection rates are increasing earlier than in previous years and rates of invasive disease in children in England, Wales and Scotland are higher than we have previously seen for this time of year. Both scarlet fever and cases of invasive disease are notifiable in England and Wales, meaning that any case must be reported to the UK Health Security Agency (UKHSA) and as such we are able to monitor rates carefully.
- Dr Claire Turner, University of Sheffield, UK.

The UKHSA reported 851 cases of scarlet fever reported in the week of 1420 November, compared with an average of 186 for the same period in previous years. How concerning is this increase, and what might be causing it?

Scarlet fever infection rates are usually higher over the winter months, rising in late December/early January and peaking over February–April, with the invasive diseases following a similar pattern. This year, however, we are seeing an increase in scarlet fever infections earlier than in previous years. At this stage, we do not know if this means infection rates will peak earlier or remain high over the winter and into the spring. It is also not clear why we are seeing such a high level of scarlet fever cases now. It is possible that there have been some changes in the Strep A bacteria allowing it to transmit better or cause invasive diseases more readily. This is something that will certainly be investigated.
- Dr Claire Turner, University of Sheffield, UK.

How can the public protect themselves from Strep A infection?

You can protect yourself from Strep A by frequently washing your hands. You can protect others by catching your coughs and sneezes with a tissue. Strep A infections can be treated with a course of antibiotics. The antibiotic course should be completed regardless of whether symptoms of illness have resolved or not. Consult the NHS and UKHSA guidelines for advice.
- Dr Alex McCarthy, Imperial College London, UK.

What symptoms should parents look out for, and when should they seek advice?

Parents should look out for sore throat, fever and a rash that feels like sandpaper when you touch their skin. Younger children cannot always articulate their symptoms well; thus, parents should also look out for their child being irritable, in addition to fever and rash. Consult the NHS or UKHSA guidance. You should call 999 or go to A&E if your child has difficulty breathing, or their skin, lips or tongue are blue, or they are drowsy or cannot wake up.
- Dr Helge Dorfmueller, University of Dundee, UK.