Princeton University just announced their seventh case of meningitis this week, declaring a campus outbreak. Fortunately, the first six infected Princeton students have recovered. The 7th remains hospitalized.

What is meningitis? It’s an infection of the lining of the brain and spinal cord. The infection can be caused by either a virus or a bacteria.

In the United States, about 4,100 cases of the bacterial type occurs each year, including 500 deaths, according to the CDC. Young adults and college students who aren’t vaccinated are most at risk.

Watch the video to find out the symptoms and how it’s treated.

Dr. Tyeese Gaines is a physician-journalist with over 10 years of print and broadcast experience, now serving as health editor for MSNBC’s theGrio.com. Dr. Ty is a practicing emergency medicine physician in New Jersey and clinical instructor of emergency medicine at Yale School of Medicine. Follow her on twitter at @doctorty.