Health officials constantly warn of the importance of good hygiene, including washing your hands frequently, to stop the spread of germs that cause flu and colds. Now you can add the risk of worms in your brain to the list of problems caused by dirty hands.

Rosemary Alvarez began experiencing numbness in her arm and blurred vision. A cat scan revealed nothing, but an MRI showed something very deep inside her brain. “Once we saw the MRI we realized this is something not good,” neurosurgeon Dr. Peter Nakaji told Phoenix’s Fox News. “It’s something down in her brain stem which is as deep in the brain as you can be.”

She was rushed into surgery where doctors expected to remove a brain tumor. What they found was a worm! Dr. Nakaji began laughing when he realized his patient didn’t have a life-threatening brain tumor. “I was so pleased to know that it wasn’t going to be something terrible,” he said.

The surgery was a success and doctors believe Ms Alvarez will have a complete recovery. How did she get the worm? Doctors said she could have gotten it from eating undercooked pork or from someone who handled food after not washing their hands after using the bathroom.

Experts note that one person with dirty hands could pass along a disease—or worms—to many people. Ms Alvarez has a few words of advice for others. “Wash your hands, wash your hands.”