Amid the coronavirus pandemic, global health authorities are on edge about the resurgence of a killer virus thought eradicated in the 1940s – scarlet fever.
Public health measures such as social distancing and school closures that were introduced to combat the coronavirus have largely put a pause on the surge, after an epidemic broke out in Asian countries in 2011. There has since been a second outbreak in the UK in 2014, and isolated outbreaks in Australia.
Experts say at least 600,000 worldwide cases have been linked to the recent outbreaks.
A University of Queensland-led team of international researchers say “supercharged clones” of the Streptococcus pyogenes bacteria is to blame for the resurgence of the disease, which has had high death rates for centuries.
UQ’s Dr Stephan Brouwer said the disease, which commonly affects children aged between two and 10, had mostly dissipated in the 1940s.
“The global re-emergence of scarlet fever has caused more than five-fold increase in disease rate and more than 600,000 cases around the world,” Dr Brouwer said.
The coronavirus has had a positive impact on limiting the spread of scarlet fever, as public health policy measures minimise infection.
“The disease’s main target – children – have been at school less and also spending far less time in other large groups. But when social distancing is eventually relaxed, scarlet fever is likely to come back,” Dr Brouwer said.
“Like the virus that causes COVID-19, Streptococcus pyogenes bacteria are usually spread by people coughing or sneezing, with symptoms including a sore throat, fever, headaches, swollen lymph nodes, and a characteristic scarlet-coloured, red rash.”
Co-author Professor Mark Walker and the team found a variety of the bacteria that had acquired “superantigen” toxins, forming new clones that have been causing modern outbreaks.
“The toxins would have been transferred into the bacterium when it was infected by viruses that carried the toxin genes,” Prof Walker said.
“We’ve shown that these acquired toxins allow Streptococcus pyogenes to better colonise its host, which likely allows it to out-compete other strains.”
The research team removed the toxin genes from the clones causing scarlet fever, and the modified “knock-out” clones were found to be “less able to colonise in an animal model of infection,” Prof Walker said.
“Just like COVID-19, ultimately a vaccine will be critical for eradicating scarlet fever – one of history’s most pervasive and deadly childhood diseases,” he said.
“We need to continue this research to improve diagnosis and to better manage these epidemics.”