At least 16 cases have been reported on campus in Bloomington since 12 February, IU spokesman Chuck Carney said Thursday.
Nine of these cases were associated with a single Brotherhood – the patients were either members of the Brotherhood or had visited the Bruderschaftshaus.
IU does not identify the Brotherhood to protect its privacy.
Carney said while mumps outbreaks at the IU are unusual, the campus had another set of mumps in 2016.
"All of our students must have two MMR vaccines (measles, mumps, and rubella) in the second semester with a religious exemption," Carney said.
Across the country, cases of measles and mumps have risen this year.
Mumps are also on the rise nationwide. The Centers for Disease Control and Prevention reported 426 cases this year on March 29, an increase of 275 cases in one month. Previously, the CDC had reported 151 cases of mumps from January to the end of February.
While the two viral infections are similar, there are remarkable differences.
Mumps are spread through the saliva or mucus through coughing, sneezing or speaking. Sharing utensils or cups can also spread the infection, according to the CDC.
It can also spread if an infected person touches objects or surfaces that are then touched by another person.
CNN Debra Goldschmidt contributed to this report.