Illinois changes definition of school COVID outbreaks to align with CDC

The Illinois Department of Public Health is recommending schools follow new federal guidance that would redefine the number of cases needed to constitute a school outbreak of COVID-19.

The IDPH’s move to adopt the Council of State and Territorial Epidemiologists’ guidance for pre-K-12 school-associated outbreaks relies on a new national recommendation that defines a school outbreak as either multiple cases comprising at least 10% of students, teachers or staff within a core group, or at least three cases within a core group, officials said.

The Centers for Disease Control and Prevention previously recommended that two cases associated with a school be considered an outbreak, officials said.

“In an effort to more confidently establish whether transmission of COVID-19 occurred in school versus another location, IDPH is following CDC’s recommendations,” IDPH Director Dr. Ngozi Ezike said in a Friday statement.

“This change in criteria will continue to identify outbreaks and help prevent further spread, but also help rule out outbreaks that are not associated with the school,” Ezike said.

A core group means only those individuals who were together during an exposure period, and could be limited to a classroom, a sports team, before/after school care, performing arts, or other groups and likely does not apply to the entire school population, IDPH officials said.

To be considered part of an outbreak in a school, cases must meet the criteria for a probable or confirmed school-associated case with a positive test result, or the start of symptoms within 14 days of each other, officials said.

These individuals are identified to be close contacts with each other while in the school setting and not another setting outside of school, and the cases must also be epidemiologically linked to the school setting or extracurricular activity, meaning they were at the same place at the same time, officials said.

Friday’s announcement marks the second time the state has changed its definition for school outbreaks. The prior definition called for at least five cases, but the state adjusted it downward to align with the prior CDC guidance.

Masks will continue to be required in Illinois schools for “students, staff and visitors to help protect the health of those in schools and prevent further transmission in the community among vulnerable populations,” officials said.

IDPH also recommends vaccination for individuals 12 years and older, including students, and school employees are required to be fully vaccinated or tested at least weekly for COVID19, officials said.

On Friday, IDPH reported 273 school outbreaks, a number that has held fairly steady for several weeks.