Health officials have confirmed four cases of swine flu at the University of Colorado and identified 85 probable cases of the virus, up from 49 last week, the university announced Friday.

The four confirmed cases were tested for swine flu, known as H1N1 virus, by state health officials in order to verify that the illnesses at CU were indeed H1N1 and not the seasonal flu, said Dr. Pam Talley, the lead clinics physician at CU's Wardenberg Health Center. The sample was random, Talley said, and the confirmations don't change the way CU is dealing with the outbreak.

The other 85 students have not been tested for H1N1, officials said. Instead, they tested positive for Influenza A. The swine flu is a type of Influenza A, but only state officials can test for it.

Eighty-five probable cases may seem like a lot, Talley said, but it's not an overwhelming number given that there are nearly 30,000 students on campus.

"It appears to be similar to a seasonal influenza outbreak," Talley said of the H1N1 cases. "We are seeing more patients than we would normally see at this time of year, but it does not appear that we are on a huge upward trajectory."

CU is still advising sick students to stay isolated in their dorm rooms or apartments and not attend classes while they're sick. The 85 students who likely have H1N1 live both on and off campus, officials said.