The federal Centers for Disease Control and Prevention tracked down 53 people who rode with the child on an international flight that came through Chicago last month.
Patients who visited a Kalamazoo hospital emergency room and a Battle Creek pediatrician office at the same time the child was at both places also were contacted by local health departments.
The child fell ill after returning from a Middle Eastern country going through a measles outbreak, said Michelle Thorne, personal health manager at the Calhoun County Health Department.
Vaccinations were given to 39 people in Calhoun County. About five people in Kalamazoo County also needed immunizations.
"It's a very big deal from public health perspective," Thorne said. "We don't want to see any further cases come out of this."
The 8-month-old, whose name and gender were not released, was recovering. The child had not yet received a vaccine for measles, which usually is given at 12 months.