The board president's office announced Sunday afternoon that the staff member was last in the Cook County Building on Friday.
RELATED: Gov. JB Pritzker in isolation after possible COVID-19 exposure, office says
Preckwinkle will take a COVID-19 test and quarantine until her results return, the office said. She is not currently experiencing any symptoms, county officials said.
Gov. JB Pritzker also had to quarantine this week, after a member of the Illinois Restaurant Association tested positive after meeting with him.
Pritzker has since tested negative for the virus, his office said.