Though the average number of mumps cases reported daily in central Ohio has fallen, the outbreak has spread to a third county in Ohio.

As of Monday, 366 cases had been linked to the outbreak in Franklin, Delaware and Madison counties, according to a Columbus Public Health press release. Of those cases, 210 cases were linked to the Ohio State outbreak.

That number is more than half of the total 438 mumps cases reported nationwide last year, according to the Centers for Disease Control and Prevention.

Columbus Public Health spokesman Jose Rodriguez said the outbreak is growing at a rate of about five new cases per day, which is down compared to six weeks ago when about eight or nine cases were reported daily.

There is typically one case of the mumps reported in Columbus per year, he said.

The onset of the first case connected to the Franklin County outbreak was Jan. 7, while the first case connected to OSU was Feb. 10.

Rodriguez said the end of the OSU school year could have played a role in the decrease of daily reported cases of the mumps, however, it’s hard to know if there’s a specific reason for the decrease.

“Outbreaks sometimes slowdown with good infection control (washing hands, staying home if you are sick and covering your cough/sneeze) and of course with people getting vaccinated,” he said in an email.

According to the CDC, those who have received two doses of the measles, mumps and rubella vaccine are about nine times less likely to get mumps than those who have not received the vaccine.

Mumps is a viral infection of the salivary glands, according to the CDC website. It can spread through coughing, sneezing or contact with saliva or mucus and can be carried without any symptoms.

Those who are affected by mumps might have swollen and tender salivary glands under the ears or jaw on the side of the face, fever, headache, muscle aches, tiredness, loss of appetite and inflammation of the testicles in men, according to the CDC.

The website also says there is no specific treatment for mumps, but it is usually gone in a week or two.