Measles outbreak could stir panic.

A third child in Minnesota has been diagnosed with measles. The rare disease was declared eliminated from the United States in 2000, which makes the Minnesota measles drama slightly concerning. All three children live in Hennepin County, and have not traveled outside of the country. Two are siblings, and one has been in close contact with the other two.

Without knowing where the outbreak started, the Minnesota Health Department has a time sensitive investigation on their hands to identify the source of the viral infection. Now the hospital is working to reach out to hundreds of families about potential exposure.

Patsy Stinchfield, RN, Children’s Hospitals & Clinics of Minnesota’s hospital’s director of infection prevention and control, said other patients may have been exposed to the highly communicable virus in the ER, according to the La Crosse Tribune.

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. The children are being treated at Children’s Minnesota hospital in Minneapolis.

What do you need to know about measles?

It is an extremely contagious respiratory infection.

It is spread by coughing or sneezing.

The virus can live on surface or hang in the air for up to two hours.

People are contagious from four days before the rash appears until four days after it shows up.

90 percent of people who are not immune to the disease will get it just by being near someone who has it.

It can can cause swelling on the brain.

The measles resurgence in the United States is due to many not getting immunized for the disease.

Complications can include pneumonia and deafness.

Twenty million people get measles annually, with the highest number of confirmed cases reported from the Philippines, according to a 2014 report by the World Health Organization.