The Minnesota Department of Health is investigating 13 cases of measles that occurred from June through September.
According to a Sept. 29 news release, the cases occurred among several families with unvaccinated children. Additionally, most of the children had a history of traveling to a country where measles is common and circulating. The most recent case did not have a reported travel history, and investigators are working to determine how transmission occurred.
All cases are in the Twin Cities area. The affected children range from as young as 2 to children in their early teens. Over one-third are pre-teen, and several children were hospitalized for treatment of measles. Thirteen cases is several times greater than the number of cases the state sees in a typical year, according to the release.
State epidemiologist Ruth Lynfield, MD, said a small drop in the immunization coverage means thousands more children could be vulnerable to disease because they are not vaccinated.
"Measles can be a very serious disease, causing hospitalizations and sometimes death. That's why it's so important to maintain high vaccination rates for measles. If the coverage rate in a setting like a childcare or school is significantly less than 85 or 90 percent, that's an outbreak waiting to happen," said Dr. Lynfield.
The possibility that the most recent case could indicate community spread prompted health officials to urge parents to make sure their children are up to date on their childhood immunizations, which include the measles-mumps-rubella (MMR) vaccine.
The U.S. declared measles eliminated in 2000, but the disease is still common in other parts of the world.