We learned Thursday that California's 41 "Purple-tier" counties are going under a 10 p.m.-to-5 a.m. curfew starting this weekend, and San Francisco is likely to join the list by early next week. The move would also shut down all gyms and places of worship once again, and prompt a ban on all indoor social gatherings ahead of the Thanksgiving holiday.

Rising COVID cases in San Francisco — in particular an uptick on Friday of 210 new cases in one day, the largest single-day leap the city has seen since a record jump of 226 cases on July 30 — mean that the city is looking at slipping back to the state's most restrictive tier for reopening by next week. This would mean that in the span of 14 days, SF would have moved from the least restrictive "Yellow" tier all the way to the "Purple" tier — confirming fears that public health officials began expressing a month ago.

San Francisco was relegated back to the "Red" tier on Monday, following two weeks in which the number of new daily cases per 100,000 residents had tripled. As of Saturday, November 14, all restaurants that had been seating patrons indoors for the past six weeks had to stop doing so.

The next step will be to limit all activities outside one's home between 10 p.m. and 5 a.m. — excluding dog walking and "essential" activities — and shutting down again many businesses that have been allowed to be open in the last two months, including gyms, movie theaters, and museums. Dr. Grant Colfax, the director of SF's Department of Public Health, gave a news briefing Friday to deliver the warning, saying the new tier status could occur as early as Sunday.

"We are in a surge that has the potential to overwhelm our local health care system ... and force us back to shelter in place," Colfax said. "Just three weeks ago we were in the state’s least restrictive tier. And now we are on track to be in the most restrictive tier. This is indicative of how fast this virus is spreading in our city."

On the good news side, San Francisco's percentage of positive tests among all individuals being tested remains at just 2% — up from 1.87% earlier this week. But the number of new cases per 100,000 has edged quickly up, leading to the change in tier status at the state level.

"People have gotten complacent," said Mayor London Breed ten days ago when she announced the re-closure of indoor dining. "This virus definitely reacts to behavior that does not follow the suggested public health guidelines around mask-wearing and social distancing."

While San Francisco still only has 46 COVID patients in hospitals — up from a low of 25 last month — Colfax warns we "could conceivably have hundreds of people in the hospital by late December or early January."

Experts suggest that as cases rise, hospitalizations rise about two to three weeks later, with approximately 12% of all cases requiring hospitalization.

Colfax further discouraged San Franciscans from gathering for Thanksgiving — saying that if you must, it should be limited to six people, with masks on, outdoors.

The statewide curfew for "Purple" counties extends through December 21, and possibly longer.

Related: San Francisco Reverts To 'Red' Tier; Five Bay Area Counties Slide Back to 'Purple' As COVID Cases Proliferate