Scientists have warned of a new strain of a 'flesh-eating' bug that is spreading globally, and has contributed to an increase in disease cases in the UK.
The group A Streptococcus bacteria typically caused minor infections, such as tonsilitis, and was readily treated with antibiotics.
However, the bug could, in severe cases of invasive infection, cause necrotising fasciitis - a condition which destroyed and ate up body tissue, and caused pneumonia and blood poisoning.
Scientists investigating the bacteria realised there had been an increase in A streptococcus infections over an 11-year period between 1998 and 2009 linked to the new, more potent sub-type, named emm89.
A surge in infections had also been reported by scientists in Japan, Canada, France and Sweden, suggesting that the strain was spreading globally.
The new strain produces more toxin than other types, but was also unique that it had apparently shed its outer capsule, which could make it more likely to cause serious invasive infections.
According to Dr Claire Turner from the Imperial College team, it was earlier thought that the outer capsule was essential to cause invasive disease.
However, she added that the lack of capsule might help the bacteria infect sufferers.
Most infections caused by strep A though unpleasant, did not pose a serious threat. These included throat infections, tonsillitis, swollen glads and ear infections.
More severe infections could cause pneumonia, sepsis, or toxic shock, and around one in four people who suffered an invasive 'flesh eating' infection did not survive.