Justin Bieber surprised fans on Friday by announcing that he’s put his tour on hold because he’s been diagnosed with Ramsay Hunt syndrome, which is causing partial facial paralysis.  Here’s what you need to know about this rare condition.

Ramsay Hunt syndrome is a rare neurological complication caused by the varicella zoster virus — the same virus that causes chickenpox and shingles.

“Ramsay Hunt is exceedingly rare. Most people come into contact with [the virus] but very few people develop Ramsay Hunt Syndrome. The incidence is five per 100,000 people per year,” Dr. Leah Croll, MD, neurovascular fellow at NYU Langone Health, tells ABC News.

It is a syndrome that can occur in anyone who has had the virus; once you’ve had it, it can still live in your nerves.

Dr. Croll explains, “Eventually, later on in life, the virus can reactivate and cause something like Ramsay Hunt syndrome. Certain situations that can be stressful…[and] other illnesses can trigger it. Sometimes, we don’t know why it happens. ”

In Ramsay Hunt syndrome, the virus is reactivated and affects the facial nerve near one of your ears. Symptoms include a painful red rash that can be on, in, or around one ear and facial weakness or paralysis on the same side as the affected ear.

Other symptoms include ear pain, ringing in the ears, hearing loss, sensation of spinning or moving, change in taste or loss of taste, dry mouth and eyes.

Treatment includes antiviral medications and oral steroids. If there is limited damage to the nerve, one should recover within a few weeks.

“The chances of recovering strength in your face are better if you initiate treatment earlier,” Dr. Croll adds. “The best thing to do for prevention is to keep up with your vaccinations including the chickenpox and shingles vaccines.”

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