BATON ROUGE, La. — More students at Louisiana State University have fallen ill with mumps, just one week after the university said it was working to stop an outbreak.

WBRZ-TV in Baton Rouge reports that LSU confirmed Monday that nine students were ill. Eight of those students live off-campus, but one person lives alone in an on-campus apartment. That single student will be quarantined for two weeks.

Last week the university alerted faculty about the outbreak and canceled a tennis tournament after a student-athlete was diagnosed with the virus.

Mumps is a contagious viral infection spreading through saliva or mucus. It typically starts with a few days of fever, headache, muscle aches, weakness, and loss of appetite. Most people will have a red rash on their face and what mumps is best known for is causing puffy cheeks and a swollen jaw.  

You don't hear about it much anymore since there has been a 99 percent decrease in mumps cases in the US since the vaccine first became available in 1967. Now, the vaccine is usually given in combination with measles and rubella. It's called the MMR vaccine.

While complications are rare, they can lead to things like hearing loss, and swelling of the pancreas, testicles, ovaries, or brain. In very rare cases, mumps can be deadly. The best defense is to make sure your vaccinations are up to date.

Most LSU students are required to be vaccinated, but the CDC said even if you've had the vaccine, you can still get mumps. Doctors aren't sure why, but the CDC claims it could be that some immune systems just don't respond as well. 

RELATED: Several LSU students have mumps; here is what you need to know about the disease

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WWL-TV reporter Erika Ferrando contributed to this report.