WATERVILLE — Colby College is experiencing a surge in COVID-19 cases as students return to the Waterville campus for the spring semester.

The college reported 106 cases on campus Thursday, including 90 students and 16 members of the faculty or staff, according to testing data Colby posts online.

Those who have tested positive are being isolated, a school official said.

The increase in cases is due to the spread nationally of the omicron variant of the virus, and to students who likely became infected prior to returning to campus, the official said.

It appears to be the highest number of cases the college has recorded since the COVID-19 pandemic began in March 2020.

Colby has imposed a number of measures to prevent the further spread of the coronavirus. Everyone on campus will be tested three times a week for the first two weeks back at school, and then twice a week afterward.

All Colby students and members of the faculty or staff must be fully vaccinated, including a booster shot, unless the college has granted an exemption.

Additionally, masks are required indoors, informal social gatherings are limited to 10 people, no visitors are allowed on campus without prior approval and those attending indoor athletic events must be part of the college’s testing program.

Colby is not the only college in Maine scrambling to respond to the spread of COVID-19.

At Thomas College, also in Waterville, students will not return to campus until Jan. 17, according to Mackenzie Riley Young, assistant director of media relations. Meantime, the college is planning additional precautions for the spring semester, including that all students will be tested, masks must be worn when inside all buildings, regardless of vaccination status, and no visitors will be allowed inside dormitories.

Last week, Bates College in Lewiston also tightened its safety protocols to limit the spread of the virus, including more-rigorous testing of students returning to campus, a booster shot requirement and holding all classes remotely for at least the first five days of the semester.