Health officials are grappling with the largest outbreak of measles in Minnesota in almost 30 years, which is mainly sickening young children of Somali immigrants who fell under the sway of anti-vaccination activists.

The state has reported 44 confirmed cases of measles since April 11, and the outbreak is the largest this year in the United States, which had essentially eradicated the disease in 2000 before discredited research stoked fears of a link between vaccines and autism.

As of Thursday, 11 patients have been hospitalized, Doug Schultz, a spokesman for the Minnesota Department of Health, said on Friday. It is the largest outbreak in the state since 1990, when 460 cases were reported. All of the patients, with the exception of an adult health care worker, were children younger than 10. Most were under 5, he said.

Measles, which can cause severe illness and death, is highly contagious, spreading through the air after an infected person coughs or sneezes. Not only does it pass through droplets in the air, but it can also linger. Infected people can also spread measles before a telltale rash of flat red spots develops.