Many of the calls and messages from my primary care patients start, unnecessarily, with an apology.

Teresa is in her 40s. She wants to let me know about thermometer readings that are higher than usual, but not quite a fever. A cough when she thinks about it. And shortness of breath — a symptom, she notes wryly, both of covid-19 and of covid-induced anxiety.

Ava, a 26-year-old graduate student with asthma, tells me she feels run down and had a sore throat earlier this week. She wonders what she can do to keep herself and her roommate safe.

Patients with known coronavirus exposure, fever, and cough call me to report their vital signs, wondering whether they are sick enough, yet, to go to the hospital.

Although my advice changes by the day or even by the hour, it goes something like this: That we don’t have enough tests. That they should assume they have covid-19, staying home and isolated for 14 days from when their symptoms began, or two days after they have resolved — whichever comes second. I tell them what alarm signs to watch for. That it is normal to feel worried. That we’re in this together.

While the nation focuses — understandably — on our hospitals’ ability to care for the coming surge of severely ill covid-19 patients, much of the pandemic response is playing out in primary care offices (and phones and computers) across the country as doctors and nurses triage precious resources such as tests and emergency care and recalibrate anxieties fueled by politicians’ mixed messages.

The pandemic is testing the capacity of a primary care system that is already short on doctors and long showing signs of wear. But it is also a time when primary care is needed to do what it does best: offer trusted advice in the face of uncertainty, tend to our patients’ physical and mental health, and help them stay out of emergency rooms and hospitals that are becoming overwhelmed.

We are seeing more than the infectious symptoms of coronavirus. Like the 37-year-old ICU nurse who has been caring for covid-19 patients wearing reused protective equipment and coming home to her infant, a husband whose business is now failing and a disabled mother at high risk of the disease. She is reaching out now because her once manageable postpartum anxiety has become severe. We decide to start her on medication and weekly phone check-ins to get her through.

Melissa, a 66-year-old woman with a finger infection, is wrapping up a course of antibiotics another doctor gave her. She tells me that her finger looks better, but not yet normal. Rather than the usual watch and wait, we have her pick up a second, just-in-case antibiotic while she still feels safe to leave her house.

For patients with urgent problems such as rectal bleeding or with chronic conditions such as diabetes and heart failure, we weigh the need for in-person care against the risk of covid-19. These trade-offs will grow increasingly difficult when we are further along in a pandemic that will be a marathon rather than a sprint.

At the same time, we worry about patients — often the most vulnerable — who will not seek help for these problems during the pandemic. And when our best advice is often to stay at home, we worry about those who do not have this luxury.

Primary care practices are scrambling to address this swell of medical needs caused or complicated by covid-19, and to adapt to the reality that the virus, enabled by test and mask shortages, has rendered office visits risky.

When my physician colleague Erika Pabo covered weekend calls for our Brigham and Women’s Hospital practice group in mid-March, she estimated we had ten times the usual call volume — 80 percent of which were related to the pandemic.

And even at our well-resourced health system, with its centralized covid-19 response, we can rarely offer what many of these patients need: a test. Instead, we deploy rapidly evolving covid-19 testing rules — their logic contorted to fit the constraints of how many tests are available that day.

“As a physician, you are trained to help and nothing is more frustrating that not being able to do so fully,” Pabo told me. “It was an eerie feeling knowing I surely talked to people with covid-19 who didn’t meet our stringent testing criteria.”

A national survey shows how widespread these issues are. “[Primary care] practices are already, in mid-March, under tremendous stress,” says Ann Greiner, president and chief executive of the Primary Care Collaborative, not-for-profit organization. She is co-leading weekly surveys of primary care doctors, nurse practitioners and physician assistants to understand how they are handling covid-19.

As of March 23, nearly half of the more than 500 survey respondents across 48 states said that they had no ability to test patients. Half also said they lacked personal protective equipment to keep staff and patients safe. This is “only magnified because in some states, governors and other state leaders are communicating to the citizens that they should go to their PCP to be tested,” Greiner said.

In response, many practices like ours are canceling most in-person visits (which is still how most doctors are paid) or shifting them to video and telephone. As of March 23, 40 percent were offering video visits in some form, while 91 percent offered phone visits.

If there is any good news to come out of the pandemic, it is that it has compelled some policy changes to support this virtual care that we should have had for a long time.

For example, Medicare just loosened restrictions on the video platforms we can use to talk with older patients (FaceTime and Skype are now in play). Massachusetts now requires insurance companies to pay equally for in-person, telephone and video visits; when these visits are covid-related, patients cannot be asked to pay.

But especially for smaller primary care practices, telemedicine is still complicated and costly to set up, and the financial losses from dropped visits will be severe.

Rebecca Etz, associate professor of family medicine at Virginia Commonwealth University and co-director of the Larry A. Green Center that co-led the survey, said she was most struck by the written-in comments she read. Many doctors did not know whether they would be able to keep their practice doors open, she told me. One wrote, simply, “please help us.”

Complicating matters further is the worrisome number of health care workers who are under quarantine (for covid-19 exposure) or isolation (for symptoms or confirmed infection). In mid-March, 20 percent of survey respondents said that doctors, physician assistants or nurse practitioners in their practice were quarantined. As of March 23, it was nearly 50 percent.

In my own unscientific Twitter survey of U.S. doctors on March 20, nearly one-tenth of the 143 who responded were home with symptoms or exposure to covid-19 (8 percent) or with confirmed infection (1 percent).

A few weeks ago, a mild sore throat, headache and chills that I’d have usually ignored prompted my own, first-ever sick day from the clinic followed by self-isolation. A camera-enabled laptop and an oversized armchair became my makeshift exam room. But like so many others, I still felt stuck between the need to limit spread to colleagues and patients and the desire to report for duty.

I’ll be glad — if nervous — when I return to work as normal, especially because it is anything but.

Ishani Ganguli is an internist at Brigham and Women’s Hospital and a health policy researcher and Assistant Professor of Medicine at Harvard Medical School.