(Portland, OR)  --  Health officials in Portland, Oregon are confirming a case of measles and they say 500 people could have been exposed.  Health experts are monitoring 40 people who were exposed and are considered to have no immunity to the disease.  Authorities say the person confirmed to have measles visited a local emergency room and was treated for a time at a childcare center in the Portland suburb of Gresham.  Health officials say anyone who was infected from being exposed to that person will begin to show symptoms by mid-July at the latest.