The Cook County Sheriff's Office reported that 42-year-old Nicholas Lee died Sunday at Stroger Hospital.
The cause of death is pending an autopsy, but the sheriff's office said preliminary reports suggest he died of cardiac arrest.
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As of Sunday, 306 Cook County Jail detainees have tested positive for the novel coronavirus, along with 218 members of the sheriff's office staff.
More than 180 of those are correctional officers, according to the county sheriff.
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The announcement comes days after the death of 51-year-old detainee Leslie Pieroni.
Pieroni's official cause of death is also pending, but preliminary reports suggest he died as the result of complications due to the virus.
The death came on the same day a federal judge ruled against the mass release of prisoners.
Roughly one week ago, 59-year-old Jeffrey Pendleton died at Stroger Hospital after testing positive for COVID-19.
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An autopsy found he died of COVID-19 infection, with hypertension and pulmonary disease as contributing factors.
Pendleton's two surviving brothers filed a federal lawsuit, alleging the county violated his constitutional rights by shackling him to a bed while he was battling the virus.
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Jeffrey Pendleton was granted a hearing to reduce his bond days before he was hospitalized, but the motion was denied.