Scientists have uncovered new details about how brain-eating amoebas infect people, tracking the creatures’ movements through tiny channels in the lab.

The study, published in the Proceedings of the National Academy of Sciences, found that Naegleria amoebas love exploring narrow nooks and crannies. In dishes containing tiny channels, the amoebas squeezed through spaces smaller than themselves and rarely left once inside.

Naegleria fowleri usually lives harmlessly in warm freshwater, hunting bacteria in pond sediment. On rare occasions it is washed up a swimmer’s nose, then crawls along nerve fibres through small openings in the skull to reach the brain, causing a usually fatal infection.

The United States typically sees fewer than 10 cases a year, and nearly every one is fatal. Infection cannot happen by swallowing water or from person to person.

Researchers say the amoeba’s innocent foraging behaviour may explain its dark side: in the wrong place at the wrong time, exploration turns deadly.