"We don't know why, but we do know that the illness tends to go in waves, and currently we are at the top of one," says Anders Tegnell, department head at Swedish Institute for Communicable Disease Control.
Symptoms are often vague and produce high fever and poor general health, which could be construed as just having the common flu.
However, at a later stage in the infection, blood poisoning may occur. The flesh-eating bacteria can also penetrate the skin through open sores and lead to the muscles. The deadly bacteria can then begin to kill tissues and "eat" its way into the body.
The infection tends to hit the elderly more often than younger people.