Measles Spread Between Two Unconnected Families in a Cook County Apartment Building, 2023

Visual summary from the CDC report.

Summary

• Measles is highly contagious and preventable by vaccine. In the U.S., 2 doses of measles, mumps and rubella (MMR) vaccine are recommended for all children, at 12–15 months and 4–6 years.
• From October 5 to November 1, 2023, five unvaccinated children aged 1–9, all old enough for the vaccine, caught measles in one apartment building in Cook County, Illinois — though their two families didn't socialize.
• About 400 people were exposed, including 13 babies too young to be vaccinated.

The first case

On October 10, 2023, the Cook County Department of Public Health was told of a suspected case in a 2-year-old who had immigrated from Yemen on September 29 and had never had MMR vaccine.

• October 5: the child went to a pediatric hospital's emergency department with fever, cough and runny nose; tests for COVID-19, influenza and respiratory syncytial virus were negative, and it was called an unspecified viral illness.
• October 8: at a second hospital, worse breathing and a positive rhinovirus/enterovirus test; the child was transferred back and admitted with breathing trouble.
• October 9: a rash appeared. The next day the family said the child had been in contact with someone with measles before arriving in the U.S.
• October 11: measles confirmed by RT-PCR; the child went home that day.

During those visits, 247 health care workers and 177 patients and companions were exposed, including 13 babies under 1, five children with weakened immune systems and one unvaccinated older child. Two of these 19 got MMR vaccine within 72 hours, and 13 received immune globulin. Of the patients and companions whose immunity could be checked, those without proof were offered protection, told to quarantine, and watched for 21 days; none caught measles.

More cases in the building

• The child's siblings, aged 4 and 9, were unvaccinated and susceptible; both developed measles in quarantine, with rashes on October 22 and November 1. Neither was hospitalized. On October 17, every resident of the building received an exposure notice.
• October 30: another 2-year-old from the same two-story building, on a different floor, was seen at an emergency department and confirmed to have measles; the rash came on November 1. The parents had declined MMR vaccine over personal beliefs and worries about side effects. This family had a different culture and language from the first, and neither family reported any contact with the other. Their units shared no ventilation, but they did share laundry rooms and entrances.
• October 31: that child's 1-year-old sibling, also unvaccinated, tested positive while having only a runny nose — after attending a child care center while ill on October 30. Fever didn't start until November 6 and the rash until November 9, so it's hard to say when this child was contagious. At the center, one 2-month-old got immune globulin, one 11-month-old got a first MMR dose, and 11 children got an early second dose.

Illinois requires MMR vaccination for school and child care, but allows religious exemptions; the child care director said forms had been filed for both unvaccinated children, though copies were never produced.

What it means

All five children were eligible for vaccine, but none had it — because of cultural barriers, limited access to care and vaccine refusal. Earlier U.S. outbreaks mostly struck close-knit, under-vaccinated communities; these two families belonged to no such network, showing that measles can spread between people who aren't social contacts at all.

Responses need culturally appropriate education, translation and ties to community leaders — slow and costly work, with a median cost of about $33,000 per measles patient in 2004–2017. As measles rises worldwide and more children have vaccine exemptions, outbreaks may become more common.

• Clinicians: consider measles in susceptible patients with fever and rash and compatible symptoms.
• Everyone eligible: children and susceptible adults should get 2 properly spaced doses of MMR vaccine.

Sources

Based on Kelley Bemis, Mabel Frias, Sheila Giovanni and others (Cook County Department of Public Health, Illinois Department of Public Health and Advocate Children's Hospital), "Notes from the Field: Measles Outbreak — Cook County, Illinois, October–November 2023," MMWR, Centers for Disease Control and Prevention; published by CDC and in the public domain; rewritten in hubnx's own words.