13 Minnesota measles cases prompt state health alert

The measles virus appears to be taking advantage of a slightly more vulnerable Minnesota, which has reported 13 infections in a year in which it would expect only one to four.

The Minnesota Department of Health alerted the public Thursday to the outbreak involving unvaccinated children ages 2 to early teens — seven of whom required hospital admission. While 12 involved recent travel to countries where measles remains endemic, one occurred in the absence of travel and raised the prospect that the virus is spreading locally.

"The measles virus is highly contagious and very successful at finding people who are unvaccinated, even within groups of people who may be vaccinated," said Dr. Ruth Lynfield, state epidemiologist.

Measles was declared eliminated in the U.S. in 2000, largely because of broad use in children of the Measles, Mumps and Rubella (MMR) vaccine. However, Minnesota saw a three percentage-point drop in MMR vaccinations among school-age children during the COVID-19 pandemic because parents scheduled fewer well-child visits.

"If the coverage rate in a setting like a child care or school is significantly less than 85 or 90 percent, that's an outbreak waiting to happen," said Jennifer Heath, state health immunizations program coordinator.

The state's last severe outbreak in 2017 involved an imported measles infection that spread to 75 mostly Somali children, largely through child care facilities in Minneapolis. The state reported only two more measles cases in the four years that followed.

The latest rash of cases took place from June through September but was more spread out among children in the broader Twin Cities area, said Cynthia Kenyon, an MDH senior epidemiologist for vaccine-preventable diseases. "On some level, we need to heighten our awareness for measles transmission and be more concerned about whether or not our children are up to date with MMR, because its not as concentrated as it was in 2017."

The two-dose pediatric vaccine is highly effective against a virus that otherwise is one of the most transmissible pathogens on the planet. One infected person on average can spread the virus to 12 to 18 others. A Minnesota investigation underscored the airborne threat of measles when it found that an infected person on the Metrodome turf in 1991 spread the virus to people high up in the stands.

Measles is spreading amid a COVID-19 pandemic, but also following the arrival of monkeypox in the U.S. and an increase in pediatric hepatitis.

Declining vaccination levels are part of the broader problem, but isolation during the pandemic also suppressed infectious diseases that are now encountering less immune resistance and more opportunities to spread, Kenyon said. "We basically have a very vulnerable community now."