A measles case was confirmed in a person who traveled to Washington, D.C., on an Amtrak train, according to the D.C. Department of Health (DC Health).

The person visited multiple locations while contagious, including the southbound Amtrak Northeast Regional 175 Train and Union Station on March 19 as well as a MedStar Urgent Care in Adams Morgan on March 22, DC Health said in a press release on Tuesday.

DC Health said it is currently working to inform people who were at these locations that they may have been exposed.

Health officials are specifying that people who are “not immune” are most at-risk of infection. This includes those who are unvaccinated or who have never contracted measles before.

DC Health did not immediately respond to ABC News’ request for comment.

“DC Public Health has notified Amtrak of a confirmed case of measles in a customer traveling on Amtrak Train 175 from New York to Washington Union Station on Wednesday, March 19,” Amtrak said in a statement on Wednesday. “Amtrak is reaching out directly to customers who were on this train to notify them of possible exposure.”

The New York City Department of Health and Mental Hygiene also released a statement on Wednesday, saying it is “aware” of the confirmed case and the patient’s travel.

“Public Health agencies routinely exchange information when exposures occur in other localities, and we are in communication with the DC Department of Health on this matter,” the statement read in part.

The CDC has confirmed 378 measles cases so far this year in at least 17 states: Alaska, California, Florida, Georgia, Kansas, Kentucky, Maryland, Michigan, New Jersey, New Mexico, New York, Ohio, Pennsylvania, Rhode Island, Texas, Vermont and Washington. This is likely an undercount due to delays in states reporting cases to the federal health agency.

Health officials are encouraging those who have never been vaccinated before to receive the measles, mumps, rubella (MMR) vaccine.

The CDC currently recommends that people receive two vaccine doses, the first at ages 12 to 15 months and the second between 4 and 6 years old. One dose is 93% effective, and two doses are 97% effective, the CDC says. Most vaccinated adults don’t need a booster.

ABC News’ Matt Foster and Othon Leyva contributed to this report.