A confirmed measles case has exposed at least 251 people in Jackson County after an infected resident rode an Amtrak train from Sedalia to Chicago on Aug. 27. The Johnson County Department of Health and Environment (JCDHE) opened an investigation after the same person visited two Overland Park businesses.

The case is one of four linked to a Missouri resident who boarded Amtrak train 318, the Missouri River Runner, that day, according to the Kansas City Beacon. Two additional cases stemmed from that initial rider: one in another passenger and one in a household contact.

The eastern Jackson County resident who tested positive had been vaccinated. Jackson County Public Health called the infection a breakthrough case, which officials described as exceedingly rare.

As we reported Tuesday, Sept. 15, the infected person visited Kyoto Sushi and Steak at 6792 W. 135th St. and Pan-Asia Supermarket at 12035 Metcalf Ave. in Overland Park on Monday, Sept. 7. The JCDHE advised anyone who visited either location that day to monitor for symptoms through Monday, Sept. 28.

Johnson County Health Director Charlie Hunt said no new cases had been identified as of Wednesday, Sept. 16, but cautioned that measles symptoms can take seven to 14 days to appear. In an Aug. 18 interview with the Beacon, Hunt said he was concerned about the broader measles resurgence: "I think we should all be worried … Quite frankly, we are still in the midst of a resurgence of measles in this country."

The 251-person exposure count covers Jackson County only. It does not include anyone in Johnson County, and health officials expect the total to grow. At least 10 of the 251 exposed people must quarantine for 21 days because they were unvaccinated or did not know their vaccination status.

The response has been enormous.

A team of six Jackson County Public Health employees worked into the night after learning of the case to trace the infected person's movements and notify anyone who had been in the same space. Jackson County Public Health had dedicated more than 150 staff hours to the response as of Wednesday, Sept. 16.

Ray Dlugolecki, assistant director of Jackson County Public Health, said the effort has pulled workers from other duties.

"That redistribution of staff also means other important public health work has had to pause or slow while the response is underway," Dlugolecki said.

The measles virus can linger in the air for up to two hours after an infectious person leaves an area, according to KCTV5. Unvaccinated people who were at either Overland Park location on Monday, Sept. 7, are advised to isolate for 21 days. Those with at least one measles vaccine dose are not required to isolate but should watch for symptoms.

Nationally, 3,294 people have contracted measles in 2026, and 95% were unvaccinated or have an unknown vaccination status, according to CDC data cited by the Beacon. In Kansas, only 90.26% of kindergartners received the MMR (measles, mumps and rubella) vaccine in 2025, below the 95% threshold needed for herd immunity.

Symptoms include high fever, cough, runny nose, red and watery eyes, white dots inside the mouth and a rash that starts on the face and spreads downward.

Johnson County residents with questions can contact the JCDHE at (913) 826-1303.