OLATHE, Kan. (AP) — Three cases of the measles have been confirmed at a child care facility in suburban Kansas City.

The Johnson County, Kansas, Department of Health and Environment says on its website Tuesday that all three cases are in children under the age of 1, who are too young to be vaccinated. The department says it has reached out to contact those at risk for the disease.

The affected children and people they have been in contact with will be excluded from the facility for three weeks.

Measles is a highly contagious respiratory disease caused by a virus. Cases in the U.S. are rare since creation of the vaccine, but the illness kills 146,000 people worldwide each year.

The disease is spread through the air by breathing, coughing or sneezing.