A new strain of scarlet fever is infecting children around the world, scientists have warned.

The resurgence of a disease that has caused high death rates for centuries has seen the number of people being struck down by the condition in England rise sevenfold in just six years.

It has been likened to Covid-19 and a vaccine will be needed to wipe it.

Supercharged 'clones' of the bacteria Streptococcus pyogenes that cause the disease are to blame, new research shows.

Lead research author Dr Stephan Brouwer, of the University of Queensland in Australia, said it has taken health authorities globally by surprise.

Scientists have warned a new strain of scarlet fever is infecting children around

An epidemic of the infectious illness - characterised by a bright red rash and a sore throat - swept Asia in 2011. Before antibiotics were available it was a major cause of death in children in the early 20th century, affecting mostly youngsters aged five to 15.

Dr Brouwer said: "The disease had mostly dissipated by the 1940s.

"Like the virus that causes Covid-19, Streptococcus pyogenes bacteria are usually spread by people coughing or sneezing.

"Symptoms include a sore throat, fever, headaches, swollen neck glands and a characteristic scarlet-coloured, red rash.

"Scarlet fever commonly affects children, typically aged between two and 10 years.

"After 2011, the global reach of the pandemic became evident with reports of a second outbreak in the UK, beginning in 2014.

Cases in England are up sevenfold in the last six years

"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."

His international team found a variety of Streptococcus pyogenes bacteria that had acquired bacterial toxins called 'superantigens' - forming new clones.

Co-author Prof Mark Walker, also from the University of Queensland, said: "The toxins would have been transferred into the bacterium when it was infected by viruses that carried the toxin genes.

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

"These supercharged bacterial clones have been causing our modern scarlet fever outbreaks."

When the researchers removed the toxin genes from the clones they were less able to cause scarlet fever in experiments on mice.

Currently outbreaks have been dampened - largely due to public health policy measures introduced to control Covid-19.

Prof Walker said: "This year social distancing has kept scarlet fever in check for now.

Scarlet fever was one of the biggest killers of children before antibiotics were developed

"And 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 eventually is relaxed, scarlet fever is likely to come back. We need to continue this research to improve diagnosis and to better manage these epidemics.

"Just like Covid-19, ultimately a vaccine will be critical for eradicating scarlet fever - one of history's most pervasive and deadly childhood diseases."

Since 2014, between 15,000 and 30,000 cases have been diagnosed in England annually - compared to 4,366 in 2013.

Infected individuals often develop a white coating on the tongue which peels away a few days later.

The highly contagious condition is spread by close contact with someone already carrying the bacteria and it can take up to five days to develop symptoms.

Last year the British Medical Journal noted the rates of scarlet fever in England had reached the highest point for 50 years.