Please Note

The Washington Post is providing this story for free so that all readers have access to this important information about the coronavirus. For more free stories, sign up for our daily Coronavirus Updates newsletter.

Getting tested for the coronavirus is not like getting a flu shot. People who are seeking a coronavirus test have to have a doctor’s referral and then have to pass the screening put in place by the hospital or clinic that’s doing the testing.

Showing up without a note from a physician or the local or state health department will not only result in disappointment, it may also delay or prevent testing for first responders, health workers and people at a high risk for death from the virus, medical authorities warn.

People being tested should also be aware that it takes from three to seven days to get results, which come from state- or privately run laboratories. Thus, new cases announced on a Wednesday, for example, probably came from tests taken a week earlier.

If you do have such a note, here is the latest list of known sites in the region where coronavirus sample collection or testing is underway:

The District

Children’s National Hospital has testing for children only in a drive-up and walk-up facility on the campus of Trinity Washington University.

A referral from a pediatrician is required, and tests are done three days per week, depending on the weather. Joelle Simpson, medical director of emergency preparedness at Children’s, said that’s to avoid contamination of the samples in case of rain.

●A drive-through test site on the campus of United Medical Center, the city’s only public hospital, will open by late next week and will be able to test up to 300 patients per day, the District’s health department said.

Kaiser Permanente’s D.C. clinic, which is located near the Kaiser Permanente Capitol Hill Medical Center, offers drive-up and walk-up testing. The sites are open for testing from 9 a.m. to 5 p.m., seven days a week.

The site — as well as Kaiser sites in the suburbs (see below) — requires a doctor’s order and appointment for the test.

George Washington University Hospital in the District’s Foggy Bottom neighborhood erected a tent to test coronavirus patients. A doctor’s order is required.

Virginia

●Virginia Hospital Center in Arlington set up a temporary drive-through site at 1429 N. Quincy St.

The location collects samples from about 60 patients per day and sends them out for testing. It is by appointment only and requires doctor-provided covid-19 test referrals. The site is reserved for Arlington residents, employees or patients of the hospital’s medical staff.

Kaiser Permanente has drive-through testing locations for its members in Woodbridge and Tysons.

The sites are open for testing from 9 a.m. to 5 p.m., seven days a week, and require a doctor’s order and appointment.

Inova Health System set up three of its urgent-care centers at Dulles South, North Arlington and Tysons to screen all patients with symptoms connected to respiratory illnesses and provide drive-through sample collection for tests that have been ordered by physicians. All three clinics are open daily, from 8 a.m. to 8 p.m.

PM Pediatrics in Fairfax County has opened drive-up coronavirus testing center at 11056 Lee Highway. Only pediatric patients who have been evaluated by a pediatric expert, either in-person or via the firm’s app, are eligible for the test. The only other site where the 55-clinic company offers the test is in Wayne, Pa.

Maryland

Kaiser Permanente also has testing sites for its members in Gaithersburg, Largo and South Baltimore, with the same hours and criteria as in Virginia.

●Adventist HealthCare Shady Grove Medical Center has coronavirus testing only for critically ill patients who are likely to need hospitalization, said spokeswoman Lydia Parris. The hospital has no community testing sites, she said.

●The National Guard last week set up a screening and testing location in the Washington Redskins stadium’s parking lot. Tests are available only by preregistration through a physician.

●Some MedStar Health centers, with multiple locations in the region, are testing for the virus. Patients are asked to call the clinic or hospital first.

Holy Cross hospitals, in Silver Spring and Germantown, have tents to triage patients with influenza-like illnesses, including the novel coronavirus.

Patients then may be tested in the emergency room, spokeswoman Kristin Feliciano said, but the hospitals are not set up to receive walk-in community members looking for tests. Anyone suspecting they have symptoms should first contact their primary care provider, and should call the hospital before turning up there.

This is a developing story. It will be updated as new information becomes available.

Erin Cox, Darran Simon and Rebecca Tan contributed to this report.