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New strain of scarlet fever-causing bacteria discovered amid surge in diagnoses

A new strain of strep A bacteria has been discovered amid a rise in scarlet fever cases, research has shown. 

Imperial College London said the M1UK strain appears to have emerged in England and Wales since 2010 to become the dominant cause of strep A infections. Publishing their findings in The Lancet’s Infectious Diseases journal, they added that the new strain is treatable with antibiotics.

The researchers said guidelines for diagnosing and treating throat infections might need to be updated to take into account the new strains and that developing a vaccine against strep A is important. 

Scarlet fever, which particularly affects young children and counts characteristic symptoms as a high temperature and sore throat, has become more common in recent years, with more than 19,000 incidences in 2016, compared to under 16,000 in 2014.

Research in collaboration with PHE identified the increase as deriving from a mutated strain of the streptococcus A subgroup emm1 – known as M1UK. Producing nine times more toxin than other emm1 strains, the M1UK strain has become the dominant cause of streptococcus A infections, including scarlet fever, sore throat and invasive infection, which can lead to sepsis.

Dr Elita Jauneikaite, first author of the new study, said: ‘There is still uncertainty around the cause of the rise in scarlet fever – and whether it is a result of practice change, population or environmental factors.

‘Research investigating the most appropriate way of reducing the burden of Strep A infections is currently underway – including work into developing a vaccine.

‘We may also need to consider whether guidelines for diagnosing and treating throat infections may need to take evolution of new strains and complications like scarlet fever and invasive infections into account.’

Last year, scarlet fever cases again climbed to their highest level in five years, with key clusters in the North East and North West of the country. At the time, PHE’s deputy director of the national infection service, Dr Nick Phin, assured that the situation was being monitored, and recommended that GPs prescribe penicillin to suspected patients.

The research comes as Public Health England has discovered 19 new bacteria which are resistant to antibiotic treatments. 

The new varieties, variants of existing bacteria known to cause UTIs, STIs and MRSA among others, were identified over the past decade via 1,300 samples from patients across the country.

This was announced in line with the five-year infectious diseases strategy from PHE, which pledged to address current and future threats to public health including antibiotic resistance and health inequalities. 

Professor Chris Whitty, who takes up his tenure as the Department of Health and Social Care’s chief medical officer this month, stressed the ‘potentially devastating consequences’ of antimicrobial resistance. 

Last spring, a NICE review additionally found that a new strep A test could help GPs to reduce antibiotics for sore throats. 


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