Updated 3:31 p.m. | Posted 12:33 p.m.
The Minnesota Department of Health is investigating three measles cases.
All three patients are toddlers from Hennepin County. State health officials say they haven't figured out how the children contracted the disease and are trying to track down anyone who may have had contact with them.
Most people who get measles in the United States have contracted the disease while traveling abroad or from someone who has recently traveled overseas. That's not the case for these children, said Kris Ehresmann, the state health department's infectious disease director.
Measles is a highly contagious disease that's prevented with vaccines. The disease initially seems like a cold, with coughing and sneezing. But those symptoms accompany a rash and high fever, and in some cases can lead to hospitalization and death.
Two of the patients are siblings; the third child has been in close contact with other two. All three were initially seen in the emergency department of Children's Minnesota hospital in Minneapolis and are currently being treated there.
The children had not been vaccinated.
Patsy Stinchfield, the hospital's director of infection prevention and control, said that the situation is troubling on many levels, including the fact that everyone who was in the emergency room while the measles patients were being seen may have been exposed.
"We have hundreds of families who we are reaching out to for potential exposures," she said. "But we have no known secondary cases from those kids."
Ehresmann said this type of public health sleuthing is important. Public health officials need to quickly identify as many people as possible who have come in contact with the children to educate them on the disease.
"If we can reach out to potential contacts early enough, and they are someone who has not vaccinated, IG and MMR vaccines can be given to try to prevent measles from developing," she said.
Most people in Minnesota are vaccinated against measles. But the state health department said immunization rates among some communities have declined in recent years.
Stinchfield said that the current outbreak should serve as a warning to parents who decline to have their children immunized.
"People who have opted out of vaccinating need to catch up and get themselves vaccinated now," she said.
Stinchfield said the consequences of measles are dire.
"We've had children at our hospital even as recently as 2011 who were in our intensive care unit, on a ventilator. It can get into your brain, it can get into your lungs, it can cause permanent brain damage," she said. "There is no medical reason not to get MMR vaccine unless you have a severe immune deficiency."