UC Davis Health announced yesterday they have sent 200 letters to people that may have been exposed to the measles virus on March 17th in their emergency department at the UCD medical center. One young girl has been diagnosed with the illness.A 0ne mother has gone to the press with concerns that her 7-year-old terminally ill son had been in the center within an hour of the Calaveras county girl who had been diagnosed with the disease was there also. UCD medical providers evaluated the boy on Tuesday and said he did not have the virus. No other cases have been reported from the center as of yesterday. Separately, placer county health officials recently reported a family of three also had measles after visiting someone in Butte County whom they later learned had the illness. Placer public health officials said none of the family members had been vaccinated against measles. One of the family members went to work out at the auburn racket and fitness club on March 18th at about 5:45 pm and health officials say that so far, their investigation has not turned up any other cases locally. The family, learning of the exposure had remained isolated at home while fighting the illness. Individuals can have the measles virus for up to 5 days before showing symptoms but most have it 12 days. Transmitting the virus can happen days before symptoms appear. Medical officials urge vaccinations as the most effective was to prevent the illness. Measles can cause deafness and death.