The Minnesota Department of Health (MDH) has declared an end to the measles outbreak of spring and summer 2017 today, with the last case identified on July 13.
The outbreak that eventually sickened 79 people, mostly children under 10 years of age, began when the first case was identified April 11.
Health officials say under standard public health practice, the outbreak can be declared over if there are no new cases identified for 42 days. The incubation period for measles is 21 days, meaning that’s how long it can take for someone who has been infected with measles to show symptoms. Health officials wait two incubation periods (42 days) out of an abundance of caution.
The outbreak was the largest measles outbreak in Minnesota since 1990 when 460 people became ill and 3 people died. In the 2017 outbreak there were:
- More than 8,000 people exposed to measles
- More than 500 people asked to stay home from school, child care or work because they were potentially infectious (unvaccinated and exposed to someone infectious)
- 22 people hospitalized
- 73 cases under 10 years old
- 71 of the cases unvaccinated for measles
- 70 cases in Hennepin County, but also three in Ramsey County, four in Crow Wing and two in Le Sueur counties.
Bringing the outbreak to an end required a major public health and community response, health officials said. It involved significant resources of staff time, energy, expertise, laboratory capacity and outreach to the affected communities. It required significant collaboration among state and local public health agencies, health care systems, schools and child care centers and even work places, as well as the Somali community.
The Minnesota Department of Health (MDH) estimated its costs for the outbreak response were more than $900,000 and Hennepin County estimated its costs at about $400,000.
Minneapolis’ Somali community was hit particularly hard by the outbreak, where 64 of the 79 cases occurred, mostly in unvaccinated individuals. Vaccination rates for measles, mumps and rubella (MMR) vaccine at the start of the outbreak hovered around 42 percent among Somali Minnesotan 2-year-olds. That allowed the virus to spread more easily among children in the community.
“This outbreak showed that preventing disease requires all of us working together,” said Minnesota Health Commissioner Dr. Ed Ehlinger. “Public health is a community, collective endeavor. It’s what we as a society do together to ensure the conditions in which everyone can be healthy.”
The outbreak also demonstrated that the public health interventions of rapid case identification, monitoring and follow-up, vaccination and exclusion, worked, health officials noted.
“Seventy-nine cases is 79 too many, but when you consider how many people were exposed and how many were susceptible, it’s clear that the interventions helped keep the outbreak from being even worse,” said Kris Ehresmann, director of infectious disease for the Minnesota Department of Health. Except for vaccination, those intervention tools were not available to public health during the 1990 outbreak, she noted.
Ehresmann said it was also clear from the course of the outbreak that the measles virus is very effective at finding the unvaccinated, but also that high vaccination rates among the entire population protect the vast majority of people in Minnesota.
“We need to remain vigilant,” Ehresmann said. “As long as measles exists elsewhere in the world and there are clusters of unvaccinated people here, another outbreak could happen. Measles is just a plane ride away. We must maintain an adequate public health infrastructure and response capability to ensure we’re prepared for the next threat.”
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