Two of the four states have dozens of measles cases as the CDC urges people to get vaccinated.
More than half of the states in the country are dealing with measles.
The latest numbers from the CDC show that 940 cases have been confirmed in 26 states.
In Missouri, the CDC says 10 cases have been confirmed.
In Oklahoma at least one confirmed case has been reported.
No word on cases in Arkansas or Kansas.
The majority of patients are children who have not been vaccinated. The hardest hit state continues to be New York where there are nearly 800 cases.