If you could forecast an earthquake weeks away, then waited those weeks in dread — that might feel like the moment now, before the coronavirus surge.

Even as the outbreak has shuttered Bay Area schools, closed public parks and sickened thousands locally, experts say the worst is still to come. Shelter-in-place efforts appear to have slowed the spread of the virus, but projections place California on the upward slope of the pandemic curve. It’s impossible to predict when the peak will hit, or how hard, but across the Bay Area people are worried about the climb, anticipating the moment infections might overwhelm the system.

We are in the shadow of the surge, potential disaster looming on the horizon.

Places where the surge has already arrived provide a grim preview of what may be coming. In Italy, sirens echo through otherwise quiet streets as ambulances carried oxygen-starved patients to inundated emergency rooms. In New York, the surge has stretched resources to the breaking point. Refrigerated trucks now collect victims of the virus, while doctors film hospital hallways full of prone patients and beg for more ventilators and protective equipment before falling ill themselves.

Around the Bay Area, frontline medical workers, religious leaders and homeless advocates are eyeing news from other regions and bracing for what’s ahead. They’re creating new protocols and contingency plans, and trying to manage anxiety as best they can while they wait for the future to sweep in.

At San Francisco General Hospital, trauma nurse Christa Duran says it’s quieter than usual in the emergency department — the calm before the proverbial storm. Patients are being rerouted to urgent care and other departments to free up space in the ER, while staff use the time to plan and prepare. They’re establishing new protocols for COVID-19 patients and pressing hospital leadership about resources like personal protective equipment and ventilators. They’re researching disinfection practices and coronavirus symptoms, watching the pandemic play out elsewhere and learning from colleagues across the country and around the world.

And they’re mentally preparing for what the surge could bring to S.F. General.

“We only have 60 ventilators and we’re already using a third, and we haven’t even had a surge yet,” says Duran. “The worst thing I can imagine is being in a place where I only have one ventilator left and I have to decide who gets it. That’s what they’re doing in Italy. In New York they’re getting close to that.”

She calls the feeling “pre-traumatic stress syndrome” — a constant current of anxiety and anticipation that has made her scared to pick up extra shifts and has invaded her dreams.

During a recent nightmare, Duran had been sent to a department she didn’t know to care for a patient dying of COVID-19. She didn’t have the supplies she needed or the key to the medication room.

“I was just standing there confused and lost,” she says. “I think that’s the feeling that everyone’s having in our heads. We can only prepare so much for the possible known.”

For Jose Ramirez, the biggest challenge is his own workforce — making sure he has enough healthy, available staff members to care for a community that relies on them. Ramirez is the executive director of St. Anthony Foundation, which offers hot meals, free clothes, shelter and medical services to homeless and low-income residents in the Tenderloin. The organization has had to adapt quickly to pandemic operations. All services are now delivered curbside, and the 100 or so daily volunteers who usually lend support have been put on hold in favor of a staff-only model.

But Ramirez says his workforce is already down 40% due to the complications of the pandemic, and he worries about burnout, morale and keeping up with client demand during the coming weeks. He has reached out to city officials about getting additional help from the national or state guard in preparation for the surge.

Even when there isn’t a pandemic, the population St. Anthony serves is high-risk. But now they’re especially vulnerable, Ramirez says. Fewer organizations are offering services, and some of the basic precautions advised to prevent the spread of the virus are nearly impossible for people living on the streets.

“I hope folks realize that the ability to shelter in place is in essence a bit of a privilege,” Ramirez says. “Those who can’t are not only at a continuous higher risk to themselves and their community, but they also have limited access to resources” like handwashing stations and showers.

Ramirez hopes filling those gaps will be prioritized and expedited to help a community in need of “services, support and, at the most important level, human connection and compassion.”

“I wouldn’t say I’m scared. I am concerned,” he says. This is a chance for San Francisco to come together, he adds. “This is really where we all learn what it means to be a community.”

At Grace Cathedral in San Francisco, the Rev. Malcolm Clemens Young is worried about what the surge will do to his community. The cathedral’s clergy have been reimagining the way they connect with congregants, reaching out via digital sermons and over the phone and giving special care to those who are most vulnerable during the pandemic: seniors, homeless people and medical workers.

“We have so many doctors and nurses in our church, and we’re talking about how to support them in particular,” he says. “It’s the one chance where they can be on the receiving end of love and care.”

Young says he’s also been preparing Grace’s clergy for the tragic work that this spring may bring: counseling congregants who lose loved ones to the coronavirus and holding small gravesite ceremonies where mourners can grieve while social distancing.

“It’s heartbreaking,” he says. “We’re even talking about what it’s like to pray the last rites over the phone.”

When he pictures the struggles of the weeks and months ahead, Young thinks of the despair that health care professionals are facing, of those who barely get by during regular times and of the senior citizens who usually attend a weekly breakfast and speaker series at the cathedral every Thursday.

“I can imagine the faces of everyone who are in that room,” he says. “I’m really worried about what’s going to happen to them, how many of them we’re going to lose to this terrible disease.”

Sarah Feldberg is assistant features editor at The San Francisco Chronicle. Email: sarah.feldberg@sfchronicle.com Twitter: @sarahfeldberg