Strep's Dangerous Cousin, Sometimes Flesh-Eating, Spreading Round World

Group A Streptococcus cells under the microscope. CDC

Group A Streptococcus (GAS) is a bacterium that infects 600 million people a year. The bug is a relative of the version that most commonly causes strep throat, but it is not confined to this area of the body. Most GAS cases are mild and involve symptoms like minor throat of skin infections, but the microbe can occasionally cause severe and even life-threatening problems such as necrotizing fasciitis (hence why it is sometimes called "flesh-eating"), where the bacteria destroys the skin.

A new virulent version of A Streptococcus, however, has been on the rise in recent years. Called emm89, it now causes as many as 1,800 serious infections per year in the United Kingdom and Ireland, and has also turned up in Japan, Sweden and Canada. One-fifth of those with serious emm89 infections die, according to a study published in the microbiology research journal mBio. This strain appears to be more likely than other GAS varieties to cause life-threatening problems like blood infections and pneumonia.

In the paper, researchers from Imperial College London noted that the number of infections caused by this strain have risen sharply in recent years. In the United Kingdom, infections increased by 80 percent between 2005 and 2007 alone. emm89 now causes one-fifth of serious strep infections in Britain.

Researchers also noted with some astonishment that, unlike other bacteria in the group, this strain has evolved to lack a "capsule," or membrane-like covering, making it more virulent.

"The fact that it had lost its capsule was a complete surprise, because it was believed that the capsule was essential for group A streptococcus to cause invasive disease," said Claire Turner, a scientist at Imperial College London who led the study, in a statement. "We know that without a capsule, they stick better to surfaces, so that may help them to transmit more easily. Another possibility is that they can more easily get inside human cells, which makes them harder to treat."

Luckily the strain remains quite easy to treat with antibiotics, for now. If it develops resistance to treatment, however, that could be a problem.