Researchers in Australia have found evidence that bacteria that live in the nose can make their way into the brain through nasal cavity nerves, setting off a series of events that could lead to Alzheimer’s disease. The work adds to the growing body of evidence that Alzheimer’s may be initially triggered through viral or bacterial infections.

Chlamydia pneumoniae is a common bacterium that, as its name suggests, is a major cause of pneumonia, as well as a range of other respiratory diseases. But worryingly, it’s also been detected in the brain on occasion, indicating it could cause more insidious issues.

For the new study, researchers at Griffith University and the Queensland University of Technology set out to investigate how C. pneumoniae might get into the brain, and whether it could cause damage once there. The team already had an inkling about how this nose-dwelling bug might make the trek.