Herpes—it’s not something that many individuals readily admit to having, but if you’ve ever had chicken pox, glandular fever or even a cold sore, you’ve been an unlucky host of the herpes virus.

In this video from Gross Science, Anna Rothschild explains how herpes stays in the human body forever once contracted, lying dormant in neurons, and how the unwanted viral guest can, on very rare occasions, cause brain damage.