WASHINGTON — Chicago’s mayor issued a new stay-at-home advisory on Thursday effective from November 16 as the United States’ third-biggest city faces a surge in Covid-19 cases.

“I’m issuing a stay-at-home advisory asking all Chicagoans to only leave their homes for essential needs, including work and school,” said Lori Lightfoot.

It comes with Cook County, which includes Chicago, seeing 91.6 new daily cases per 100,000 people on a seven-day moving average, according to data compiled by the Harvard Global Health Institute dashboard.

Anything above 25 cases per 100,000 is considered to be in the “red zone,” indicating the highest levels of risk.

The new advisory asks that residents remain confined to their homes except to go to work or school.

Residents have been asked not to have guests at their homes, to cancel Thanksgiving celebrations and to avoid travel.

“Every single one of us needs to step up and ‘Protect Chicago’ right now, or 2020 could go from bad to worse — we could see tens of thousands more infections, an overwhelmed healthcare system and 1,000 more Chicagoans dying from Covid-19 by the end of the year,” a note on the city’s website said.

The state of Illinois, where Chicago is located, reported 12,657 new cases on Wednesday, as well as 145 deaths. The state’s totals are 523,840 cases and 10,434 deaths.

On its website, it advises state residents to stay at home for the next three weeks as much as possible, “leaving only for necessary and essential activities, such as work that must be performed outside the home, Covid-19 testing, visiting the pharmacy, and buying groceries.”

The United States is experiencing its third and worst-by-far spike in Covid-19 cases.

The seven-day moving average is currently about 125,000 cases, more than 65,000 people are hospitalized, and the seven-day average of deaths is exceeding 1,000, according to data from the Covid Tracking Project.