Health workers in Grant County, in Wisconsin's southwest corner, say two adults have mumps.
This as doctors in Iowa warn a mumps epidemic could be jumping to neighboring states.
Last week, health leaders in Iowa reported almost 250 confirmed, probable and suspected cases.
Even though many of the patients had been vaccinated, the vaccine is only 95 percent effective.
College students make up the greatest number of patients, but the virus can target anyone.
Symptoms include fever, headache, muscle ache, and swollen glands near the jaw.
There's no word on how the outbreak started.