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Notes from the Field: Measles Outbreak --- Hennepin County, Minnesota, February--March 2011
On March 2, 2011, the Minnesota Department of Health (MDH) confirmed measles in a Hennepin County resident aged 9 months. As of April 1, investigation of contacts and heightened surveillance had revealed a total of 13 epidemiologically linked cases in Hennepin County residents. Of those cases, 11 were laboratory confirmed, and two were in household contacts of confirmed cases and met the clinical case definition for measles.
The patients included children aged 4 months--4 years and one adult aged 51 years; seven of the 13 were of Somali decent. Eight patients were hospitalized. Vaccination status was known for 11 patients: five were too young to have been vaccinated, and six (all of Somali descent) had not been vaccinated because of parental concerns about the safety of the measles, mumps, and rubella (MMR) vaccine. The most recent rash onset was March 28. An additional, unrelated case of measles was confirmed in a Hennepin County resident aged 34 years who was exposed in Orlando, Florida, sometime during March 1--10.
The investigation determined that the index patient was a U.S.-born child of Somali descent, aged 30 months, who developed a rash February 15, 14 days after returning from a trip to Kenya. The patient attended a drop-in child care center 1 day before rash onset; measles developed in three contacts at the center and in one household contact. Secondary and tertiary exposures occurred in two congregate living facilities for homeless persons (four patients), an emergency department (two patients), and households (two patients). A virus isolate from the index patient was genotyped at CDC as B3, which is endemic in sub-Saharan Africa.
Outbreak control efforts have included following up with potentially exposed persons, providing immune globulin to persons without evidence of immunity, and recommending that persons without evidence of immunity who have been exposed to measles not leave their residence while potentially infectious (21 days). Multiple vaccination clinics have been held or scheduled at community venues and in the congregate living facilities.
In the United States, MMR vaccine normally is given as a 2-dose series, with the first dose at age 12--15 months and a second dose at age 4--6 years.* However, this series may be accelerated during outbreaks. In response to the current outbreak, MDH has recommended that children aged 6--11 months living in selected congregate living facilities receive a dose of MMR vaccine,† and that older children and adults in these facilities receive vaccine if they are susceptible and have had less than 2 doses of MMR vaccine. MDH also has recommended an accelerated vaccination schedule (a total of 2 doses of MMR vaccine separated by at least 28 days) for all children aged ≥12 months living in Hennepin County and all children of Somali descent living in the wider Minneapolis-St. Paul metropolitan area.
Measles was declared eliminated from the United States in 2000. However, importations of measles from other countries still occur, and low vaccination coverage associated with parental concerns regarding the MMR vaccine puts persons and communities at risk for measles. Public health and health-care providers should work with parents and community leaders to address concerns about the MMR vaccine to ensure high vaccination coverage and prevent measles.
Hennepin County Public Health, Hopkins and Minneapolis; Minneapolis Dept of Health; Minnesota Dept of Health, St. Paul, Minnesota. Div of Viral Diseases, National Center for Immunization and Respiratory Diseases, CDC. Corresponding contributor: Ruth Lynfield, MD, Minnesota Dept of Health, 651-201-5414, firstname.lastname@example.org.