What is E coli, and how can you prevent yourself from becoming infected by it?

A double quarter pounder with cheese and fries at a McDonald's restaurant in El Sobrante, California, on 23 October. Photograph: Bloomberg/Getty Images

Health authorities are investigating an outbreak of E coli infections linked to McDonald’s Quarter Pounder cheeseburgers in 12 states in the US midwest and mountain west.

At least 75 people have been sickened, 22 people hospitalized and one died, according to the Centers for Disease Control and Prevention (CDC). While the investigation is ongoing, here’s what authorities currently know about how people might have been sickened and what to do about it.