Cook County Health officials are warning that hundreds of thousands of Chicago-area residents could lose their health insurance if the nation’s highest court repeals the Affordable Care Act.

The U.S. Supreme Court is expected to hear arguments in a Trump administration challenge to Obamacare a week after the Nov. 3 election. If the administration prevails, people with pre-existing conditions would lose protections, and insurance for 22 million people nationwide would be gone.

Across Illinois, nearly 630,000 people are now on Medicaid under the ACA and could lose their insurance. Half of them live in Cook County.

The county government would have to reckon with a grim future for the health insurance program it was able to create under the ACA, known as CountyCare. The health plan has about 370,000 members.

Of those, around 94,000 became newly eligible for Medicaid under the ACA. This group, who are adults with no children, would lose coverage if the ACA is repealed, officials said at a news conference Wednesday.

Another 214,000 Cook County residents are enrolled through other Medicaid programs that were expanded under Obamacare. That means a total of more than 300,000 residents could lose coverage if the ACA is repealed, officials said.

“This is yet another hit on Black and brown communities who disproportionately comprise the Medicaid population in Cook County and who have experienced the most negative impact of COVID-19,” said Debra Carey, interim CEO of Cook County Health, the government-run health care system that oversees CountyCare.

“But if the impact on people’s lives doesn’t resonate, perhaps the financial impact will,” she said.

Officials also announced an estimated $1.4 billion loss if the ACA is fully repealed. The estimate is based on lost Medicaid reimbursements and increased expenses if the county is forced to care for more uninsured patients than it already does.

Cook County Health is already the biggest medical safety net for the poor and uninsured in the county. And the county health system is already struggling to bear the burden of providing medical care to patients who can’t or won’t pay their medical bills.

When asked whether the county has a back-up plan if the Affordable Care Act is fully repealed, Democratic Cook County President Toni Preckwinkle said: “The short answer is no.”

“We have made it quite clear what our position is, and we hope that our view of health care in this country carries the day,” she said.

Trump’s newest supreme court nominee, Judge Amy Coney Barrett, has been highly critical of previous Supreme Court rulings that have allowed Obamacare to survive. Barrett’s confirmation hearings in the U.S. Senate are set to begin next week – about a month before the high court is set to hear arguments in the Obamacare case.

Mariah Woelfel is a general assignment reporter at WBEZ. You can follow her on Twitter @MariahWoelfel.