UPDATE (8:45 a.m., March 24): Harris County Judge Lina Hidalgo issued a stay-at-home order Tuesday morning, closing most businesses for the county until April 3.

Harris County Judge Lina Hidalgo on Tuesday morning is expected to order most residents to stay home except for groceries and errands, or if they work in essential industries, in order to slow the spread of the novel coronavirus, county officials with direct knowledge of the plan said.

The directive, which would take effect at 11:59 p.m. Tuesday and apply to unincorporated Harris County as well the city of Houston and other municipalities, would restrict businesses deemed non-essential through April 3.

County officials on Monday evening were working to complete a list of exempt businesses, which will include markets, pharmacies and other stores necessary for daily life to function.

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Churches will be limited to online-only services, the officials said. Parks will remain open, except for high-traffic areas like playgrounds.

Without a mandatory order limiting public interactions, Houston-area hospitals are at risk of being overrun with coronavirus cases, public health officials said. Medical experts for days have urged Harris County to take such a step.

“The facts are clear,” William McKeon, president and CEO of the Texas Medical Center, told the Chronicle. “Earlier and more aggressive restriction of public movement is much more effective at reducing community spread of COVID-19 than later and less aggressive restrictions. We must come together by standing apart.”

Hidalgo plans to announce the order at a news conference at 8:15 a.m. Tuesday. Houston Mayor Sylvester Turner declined comment Monday evening, though a spokeswoman said he would attend the announcement.

County leaders in Bexar, Travis and Galveston counties also plan issuing similar directives, their leaders said. Fort Bend County closed some businesses. Dallas County Judge Clay Jenkins issued a shelter-in-place order Sunday.

By Monday, the Houston area was the most populous in the country without a shelter in place order.

In a highly unusual move, chief executive officers of the Texas Medical Center on Monday unanimously and strongly called on civic leaders to invoke such an order to further reduce community spread of the new coronavirus, which has now infected nearly 800 people in Texas and caused nine deaths. The leaders came to the consensus during their daily teleconference on COVID-19, the disease caused by the virus.

Doctors and health experts across the country have said such orders are necessary to prevent COVID-19 from spreading so rapidly that it overwhelms the nation’s health care system. McKeon of Texas Medical Center said Monday morning the presidents of TMC hospitals and other institutions were “unanimous in our strong recommendation to move to shelter in place.”

Already, 35 states have instituted statewide closures of non-essential businesses, according to the National Governors Association.

Hidalgo said at a news conference Monday morning her office was working on a possible stay-at-home order and seeking the advice of other local leaders including Turner.

Hidalgo on March 11 issued a disaster declaration that gives her broad authority to issue a shelter-in-place order or establish a curfew. The most drastic step Hidalgo and Turner have taken to date is an order a week ago closing bars and clubs and limiting restaurants to takeout and delivery for 15 days.

Hidalgo justified that step by expressing dismay that many county residents were ignoring health officials’ advice to avoid crowds. Dr. Umair Shah, the county’s public health director, said Friday it was too soon to tell whether social distancing measures taken to date have been effective in preventing a spike in coronavirus cases.

The Harris County directive would come on the heels of Dallas County Judge Clay Jenkins’ shelter-in-place order Sunday, which allows residents to go on walks, get groceries and medicine, and visit businesses deemed to provide “essential” services.

The Dallas County order provides an expansive definition of businesses that are considered essential, including take-out, drive-through delivery business at restaurants and breweries, construction crews, banks, warehouse and hardware stores, liquor stores, laundromats, auto supply and repair shops, childcare centers, businesses that supply products needed for people to work from home, and businesses that deliver groceries and other goods.

Hidalgo said Monday if the county issues such a directive, calling it a shelter-in-place order is “not the right term” because it “evokes hurricanes, chemical incidents, makes you think of an active shooter drill.”

Turner noted on Monday that a number of venues and events in Houston — schools, gyms, theaters, clubs, arts events, conferences, conventions — have already been closed or postponed, while restaurants and bars are limited to takeout orders.

Seven of the 10 largest cities by population are under a lockdown-type order.

On Sunday, Gov. Greg Abbott declined to issue a statewide shelter-in-place order at a news conference announcing other coronavirus-related measures. He has already recommended against gatherings of more than 10 people, closed schools and restricted restaurants and bars to takeout orders.

There were 164 known cases of COVID-19 in the Houston region by Monday evening and 812 such cases across Texas, according to a Chronicle database.

Todd Ackerman contributed to this report.

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