Five babies under the age of 1 have been infected with measles in a cluster at a suburban Chicago daycare center, officials said Thursday.
They said it's not yet clear if the outbreak is linked to the Disneyland measles outbreak, which has spread to dozens of people in at least 14 states.
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"We do expect that there will be more cases associated with this daycare," Dr. Kiran Joshi of the Cook County Department of Public Health told a news conference.
"At this time, the source of infection for the children is not known. Health officials have taken extra precautions to limit the spread," Illinois Department of Public Health and the Cook County Department of Public Health said in a joint statement.
"All students, staff and faculty at this facility have been notified and anyone who has not received the MMR (measles, mumps, rubella) vaccine has been instructed to remain at home and away from unvaccinated individuals for the next 21 days."
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The Centers for Disease Control and Prevention says more than 100 measles cases have been reported in the U.S. this year so far, most linked to the Disneyland outbreak. Most cases are among people who haven't been vaccinated by babies under the age of 1 are too young to have been vaccinated.
Last week, Illinois officials reported one suburban Cook County resident had confirmed measles. That was the state's first case of 2015.