The bacteria, Rickettsia helvetica, was found when a middle aged woman became sick with meningitis. The women sought medical help after a couple of weeks of pain and discomfort but no recognised infectious agent, such as the TBE or herpes virus, was found, Uppsala Nya Tidning reports.
"Some researchers have argued that Rickettsia helvetica is presumed to be harmless, but we are the first in the world to be able to show that the bacteria prevalent over large areas of the world can cause meningitis," said physician Kenneth Nilsson to the newspaper.
The new discovery, by Nilsson and his colleagues at Uppsala University Hospital, Falun Hospital and Mälardalen University, was reported in the US medical journal Emerging Infectious Diseases.
Bacterial meningitis is a life-threatening disease. Between 150 and 400 cases occur each year in Sweden.