(NBC News) — As the coronavirus pandemic started spreading across the globe so did reports of people having strange, disturbing and vivid dreams.

Experts say not to worry. Anxiety can be a trigger.

“It’s our brain trying to clean out the files in a way, and storing things,” says Cleveland Clinic sleep psychologist Dr. Michelle Drerup.

Dr. Drerup say dreams don’t always make sense, and we still don’t know a lot about why we dream.

“We don’t have the real understanding of why we dream, and that is hard to determine because we’re only able to understand what people tell us and what they recall about their dream,” she notes.

Dream researcher Diedre Barrett conducted a recent survey where respondents recalled dreams with images of tsunamis, lethal injection and masses of white worms.

“Bug attacks have been the most interesting cluster,” she says. “There were dozens and dozens of every kind of bug in the world coming after dreamers.”

Barrett says the bugs make sense. We often refer to being sick as coming down with a “bug.”

And all dreams aren’t scary.

“People dream they have invented a cure or someone else has,” she says.

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