A woman from La Plata County who tested positive for mumps may have received the disease when she took a trip to the Midwest.
That's where thousands of mumps cases have been reported.
The woman's case was reported by the San Juan Basin Health Department on Monday.
So far, at least three cases have been reported in Colorado.
Joe Fowler, an epidemiologist at the San Juan Basin Health Department, says mumps is generally NOT a life-threatening illness, though it could lead to complications such as hearing loss.
Mumps is a viral infection in the saliva.
Early symptoms of the sickness include a low-grade fever, headache and muscle aches.
The contagious disease also causes painful swelling below and in front of the ears.