Minnesota's 2017 measles outbreak came to an end on Friday, but only after sickening 79 people, sending 22 to the hospital and triggering a major epidemiology campaign that required dozens of public health workers and community volunteers.

The Minnesota Department of Health spent more than $900,000 to curb the outbreak, the state's largest since 1990. Hennepin County, where most of the cases occurred, dispatched 89 staff members to interview affected families at a cost of about $400,000.

"Although many of us grew up thinking that measles was a mild childhood illness, the reality is that measles is a very serious disease," Health Commissioner Dr. Ed Ehlinger said Friday afternoon at a news briefing.

Ehlinger said the state was fortunate that no one died, although more than 20 required hospitalization because of complications brought on by the infection.

Health officials declared the outbreak over after the state went 42 days without a new case. The incubation period for measles is 21 days, and standard practice in public health is to wait until two such periods have passed without a new infection.

The outbreak also threw a light on low vaccination rates among children in the Twin Cities Somali community, where immunizations plummeted after a discredited rumor several years ago that vaccines can cause autism.

Altogether, 71 of the 79 cases occurred in people who were unvaccinated for measles, a trend that caused the department to launch a major vaccination outreach effort. The effort produced a surge in vaccinations among Somali children. Overall, before the outbreak was detected, about 2,800 people received measles shots each week across the state. But once public health departments stepped up efforts, the state recorded two weeks in which more than 10,000 shots were given.

Ehlinger said the department will continue to work with both the Somali community and other groups to increase vaccination rates — especially for the MMR vaccine that protects against measles, mumps and rubella.

Low vaccination rates in some groups make Minnesota vulnerable to future outbreaks because the infection can arrive with travelers from countries with active measles epidemics, then spread to people who lack immunity.

Eventually, the control effort included day-care providers, schools, health care providers and Somali community leaders.

"Without partnerships and the leadership of the Somali community we would not be here today," state infectious disease director Kris Ehresmann said.

Racing to catch up

Although the first case was identified in the second week of April, in an unvaccinated Somali-American child who had developed the characteristic measles body rash, the Health Department's disease detectives believe that child first became infected at the end of March.

That meant the highly contagious disease had about 10 days to spread unabated to other unvaccinated children before public health officials could take steps to protect them.

Most of the infections occurred at child care facilities, but others happened in health care settings, family homes and general community contact.

It doesn't take much for an unvaccinated person to catch measles; the virus can linger in the air for several hours even after an infected person leaves a room.

Once the disease was discovered, the public health community launched a full-scale effort to identify anyone who might have been exposed to the early cases, and then find those who lacked immunity to the disease.

Out of a contact group of more than 8,400 adults and children, more than 500 were identified to be at risk.

They were asked to voluntarily stay home from school, work and other public places in an effort to stop the disease from spreading.

The state's disease testing laboratory, the only one in Minnesota able to test for the measles virus, processed nearly 1,000 samples.

In the end, it was the largest measles outbreak to hit Minnesota since 1990, when 460 were sickened and three children died. It is also the second state outbreak this decade; in 2011, 26 cases were found.

"A measles outbreak can happen any time as long as there is measles anywhere in the world and there are clusters of unvaccinated individuals," Ehlinger said.

Glenn Howatt • 612-673-7192