Patients and visitors at HCMC in Minneapolis may have been exposed to measles earlier this week when three infected children sought care at the downtown hospital.

The Minnesota Department of Health issued a public alert Friday for HCMC patients or visitors to check their vaccination status and monitor for symptoms if they received care from 11 p.m. Tuesday to 6 a.m. Wednesday. The children were infected during a visit to a European country where measles is more common but did not attend local schools or child care facilities where they could have exposed others, the state health department reported.

The children, siblings all younger than 10, were briefly admitted to the hospital but have been discharged.

The number of possible exposures at the hospital is unclear, but doctors have been alerted to the potential spread and will be watching for measles symptoms and asking sick patients if they recently sought care at HCMC. Symptoms typically emerge within seven to 21 days of exposure. People at risk for exposure can be considered for treatment with immune globulin therapy that boosts immunity.

Measles is one of the most contagious diseases on the planet, causing initial cold and fever symptoms followed by a characteristic rash that often spreads from the head to the rest of the body. The ease of airborne transmission of the virus was famously documented by a 1991 outbreak during a Special Olympics event at the Metrodome in Minneapolis where measles spread from an athlete on the field to fans in the upper stands.

The spread is limited in Minnesota because more than 92% of children are vaccinated for measles by 2 years old, but the infection still finds susceptible pockets across the state. Nine cases have been reported so far this year in Minnesota. In 2017, an outbreak in Minnesota started among unvaccinated Somali children in child care sites and infected 75 people.

Measles rates are highest in Asian countries but elevated rates have been detected in European nations such as Romania, Ukraine and Greece. International travelers are encouraged to make sure they have received two doses of the measles vaccine.

The state alert to doctors Friday listed the vaccination status of the three infected children as unknown. They weren't infectious during travel, the alert stated, but only upon their return to Minnesota and during their interaction with relatives at home in Anoka County and at the hospital.