Could Scarlet Fever be Making a Comeback?

The characteristic rash of Scarlet Fever. Source: Mayo Clinic
  • Scarlet Fever commonly affects children aged 2 to 10 years.
  • The United Kingdom (UK) and North-East Asia recently reported outbreaks of scarlet fever. 
  • A study published in the journal Nature Communications blames the resurgence of the disease on supercharged “clones” of the bacteria that cause the disease. 

Scarlet fever, or also known as scarlatina, presents with a sore throat, fever, and a characteristic red rash. It occurs as a result of infection with group A streptococcus bacteria, Streptococcus Pyogenes.

The disease spreads via respiratory droplets mostly produced during coughing and sneezing. It may present as a mild case or progress to severe complications such as rheumatic heart disease, arthritis, and kidney disease. 

Scarlet fever was once a leading cause of death in children. However, the discovery of penicillin almost eradicated the disease in the 20th century.

The Resurgence of Scarlet Fever

Recent outbreaks of the disease hint to a possible resurgence of Scarlet Fever. The UK, Hong Kong, and now Australia all reported outbreaks of the disease recently.

The UK reported its highest number of cases between 2014-2018. A mutated strain of Strep Pyogenes was identified in a high number of cases in the 2014 outbreak. They discovered the new strain produced a toxin nine times more dangerous than the previous strain.

This global re-emergence of scarlet fever has caused a more than five-fold increase in disease rate and more than 600,000 cases around the world.

Dr. Stephan Brouwer

A team of researchers from the University of Queensland identified new clues about bacterial strains identified in the outbreaks. They discovered the outbreaks occurred as a result of supercharged bacterial clones of the bacteria. 

Supercharged ‘Clones’ Identified

Researchers found that the bacteria acquired ‘superantigen’ toxins, forming supercharged clones of Strep Pyogenes. According to co-author Professor Mark Walker, the toxins transferred into the bacteria when a virus carrying the toxin genes infected it.

We’ve shown that these acquired toxins allow Streptococcus pyogenes to better colonize its host, which likely allows it to out-compete other strains.

Professor Mark Walker

With lockdown policies in place in countries across the world, scientists believe the threat has greatly reduced. However, once the social distancing measures relax, a resurgence of the disease can be expected. 

A vaccine for Scarlet Fever will ultimately eradicate the disease. Therefore, continued research is required to help control possible epidemics of the disease.


Brouwer, S., Barnett, T.C., Ly, D. et al. Prophage exotoxins enhance colonization fitness in epidemic scarlet fever-causing Streptococcus pyogenes. Nat Commun 11, 5018 (2020).


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