A healthcare worker in PPE gives a man a coronavirus test using a swab up the nose.
A healthcare worker gives a man a coronavirus test at a pop-up testing site in Pembroke Park, Fla.

COVID-19 has sickened millions of Americans and claimed the lives of more than 150,000. At this point, its relentless spread can feel inevitable. But that’s a “false narrative,” says Tom Tsai, M.D., a surgeon at Brigham and Women's Hospital in Boston and an assistant professor of health policy and management at the Harvard T.H. Chan School of Public Health.

“The pandemic is not fated to run a certain course,” Tsai says. “We can change it through really good public health practices.” While there’s often a focus on important individual actions, such as social distancing and wearing a mask, public health measures—in particular, diagnostic testing—are also key to changing the course of the pandemic.  

Diagnostic tests identify who is actively infected with the coronavirus that causes COVID-19. They are different from antibody tests, which can show if you were infected with the virus at some point in the past.

When the pandemic first hit the U.S., tests were scarce. They were reserved for those who were seriously ill, says Kelly Wroblewski, M.P.H., director of infectious disease programs at the Association of Public Health Laboratories. But, she says, “by early summer, testing capacity had increased rapidly—we were in a much better place."

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The Food and Drug Administration authorized the first commercial diagnostic test on March 12. As of Aug. 4, the agency has authorized 166 and says that many more are coming. 

Unfortunately, in much of the country testing is still not going smoothly, because companies that make the supplies for tests and the labs that process them are struggling to keep up with demand. "Due to the increase of COVID-19 cases in the U.S., all the hotspots, we've just seen this spike in demand for testing," Wroblewski says. In some areas, that's led to test shortages or major delays in results, with many people waiting a week or longer for results.

Such delays make tests a far less useful tool for slowing the spread of the virus.

As a result, some states are once again restricting who can get a test, leading to conflicting public health messages, Tsai says. The hope, he says, is that the U.S. will be able to increase capacity over the next couple of months so that testing becomes routine.

Here’s what you need to know about tests to diagnose COVID-19. 

Why Is Testing Important?

Diagnostic testing is key to containing COVID-19, says Jennifer Nuzzo, Dr.P.H., a senior scholar at the Johns Hopkins Center for Health Security. “As states are starting to open up, we don’t want to find ourselves back where we started when we were all told to stay home,” she says.

The way to avoid that, Nuzzo says, is to identify people infected with the virus and make sure that they stay home and isolate themselves. Then, through a process called contact tracing, public health workers get in touch with people exposed to the infected person and encourage them to isolate and get tested as well. Widespread testing is especially important with COVID-19, because an estimated 40 percent of infections are transmitted by people without symptoms.

“People often think of COVID-19 spreading from one person to two and then to four and eight and so on,” Tsai says. But in reality, one person can spread the disease to many others, who each can infect several more. “With effective public health interventions, he says, “we prevent one case from turning into a large cluster.”

To effectively interrupt disease transmission, testing must be combined with not only contact tracing but also measures such as masking, physical distancing, and even potentially additional shutdowns, Tsai says. 

Who Should Get Tested?

The Infectious Disease Society of America (IDSA) advises getting tested if you have symptoms of a COVID-19 infection: fever, cough, shortness of breath, chills, muscle pain, new loss of taste or smell, vomiting or diarrhea, or a sore throat. (Call 911 if you have severe symptoms, which indicate a medical emergency, according to the CDC: significant trouble breathing, persistent pain or pressure in the chest, sudden confusion, or bluish lips or face.)

If you don’t have symptoms, public health authorities generally recommend testing if you came in direct contact with someone infected with the SARS-CoV-2, the virus that causes COVID-19, or if you live or work in an environment with known COVID-19 cases.

In addition, many hospitals, nursing homes, and other healthcare facilities require testing before admitting patients.

Public health recommendations for testing other people without symptoms vary by region, depending on the rate of COVID-19 infections as well as the availability of tests. Where possible, it also makes sense to get tested if you have been around a lot of people—say, at a protest or other large gathering.

If you plan to travel, check restrictions: Some states require a negative COVID-19 test, a mandatory quarantine period, or some combination for visitors. That's also true of most international destinations, although the CDC advises against all nonessential international travel.

Some groups—including White House staffers and professional sports players—already undergo regular COVID-19 testing, but "access to testing shouldn't just be reserved for celebrities,” Tsai says. "For universities, testing will be a critical strategy to ensure students and faculty are safe. And in factories, where workers are working indoors or the ability to physically distance may be limited, then testing along with masking can help."

Where Can You Get Tested?

That depends on where you live. To find out whether you qualify for a test and where to get one, check with your primary care doctor or local health department. Castlight Health, a company that helps people navigate health benefits, also provides an online test locator.

Some areas have drive-through or walk-in testing sites; in others, you may need an appointment and a referral from a healthcare provider.

You can also get a test shipped directly to you at home. You’ll swab the inside of your nose or spit into a test tube and send your sample to the lab using prepaid expedited shipping. As of Aug. 4, the FDA has authorized more than 15 at-home COVID-19 tests. Some of the first tests available were from Everlywell, hims & hers, Pixel by LabCorp, Vault, and Vitagene. In each case, you fill out an online form to see whether the test is available in your state and whether you qualify.

Though there’s still some question about whether home-collection tests are accurate and prompt enough, they have advantages, Nuzzo says. “You can reduce the number of sick people who have to show up in a public place to get tested,” she says. “And it removes some of the burden on the health system.”

One caution: The FDA has warned about companies selling fake or unproven tests for COVID-19. If you order a test, make sure that it’s authorized by the FDA

What Does the Test Involve?

SARS-CoV-2 attacks your respiratory system, so tests typically look for the virus in cells collected from your nose and throat. Most often, a healthcare worker inserts a 6-inch swab through your nostril to scrape cells from your nasopharynx, the upper part of the throat behind your nose. “It's quick but a little uncomfortable because the swab needs to go all the way into the back of the nose,” Wroblewski says.

A simpler technique, which calls for swabbing only an inch or so into your nose, is gaining popularity because it's less invasive and easier to tolerate, says David Pride, M.D., associate professor of pathology at the University of California San Diego. "It also gives you more flexibility on the actual swab that you use for testing, which is critical amidst all the nationwide swab shortages," he says.

Another advantage to the simpler nasal swab is that it doesn't take special training to administer. You may even be asked to do it yourself. “To get a really good specimen, make sure you apply a little pressure to the inside of the nostril to collect as many cells as you can,” Wroblewski says.

Though the deep nasal swab is considered the gold standard for picking up viruses, guidelines from the IDSA concluded that shallower swabs work almost as well and are an acceptable alternative. 

To be thorough, healthcare providers may also swab the back of your throat. That area tends to contain less of the virus, though, so throat swabs should typically only be used in conjunction with nasal swabs, according to the IDSA.

One promising approach, now used in some home-test kits, is to test saliva by having you spit into a test tube. That's easier and simpler than a swab, but saliva doesn’t contain as much virus as other types of samples, Pride says. "It's still a bit early for saliva tests," he says. Preliminary research on the accuracy of the testing method is mixed. As of August 17, the FDA had given emergency use authorization to five saliva-based tests.

How Long Does It Take to Get Results?

It depends on the type of test you get, as well as the backlog for processing tests in your area. 

The FDA has authorized a handful of "point-of-care" COVID-19 tests that return results in less than an hour—often in minutes. Like rapid tests for flu or strep, these are convenient in that they provide a quick answer, but they also miss more infections than tests processed in a lab, Wroblewski says. "You sacrifice some accuracy for speed."

If you are tested in a hospital or other facility that has labs onsite, you can expect results within a day or two, Wroblewski says. Typically, the turnaround time for commercial labs is three or four days, she says. But due to both increased demand and shortages of supplies needed for processing, lately it's been taking longer—sometimes far longer—for many patients.

new national survey found that while most people received the results from a swab test within three days, 10 percent of respondents said they waited 10 days or longer. Hispanic and Black Americans typically had longer waits than whites, the survey found. 

The main commercial labs have responded by prioritizing certain tests, such as those for hospitalized patients or healthcare workers with COVID-19 symptoms.

If you have a choice about where to get tested, you can call around to find out which site has the shortest estimated turnaround time, Wroblewski says. But keep in mind that if you go out of your health insurance network, you may have to pay upfront for the test and file for reimbursement. 

What Do the Results Mean?

A positive result, indicating that you are infected with SARS-CoV-2, is very reliable, while a negative result is less certain, Pride says. In other words, false negatives are more common than false positives.

That's especially true with the rapid COVID-19 tests. According to FDA specifications, point-of-care tests can miss the virus—that is, be falsely negative—as often as 1 out of every 5 times. If you have symptoms and a quick test yields negative results, the agency recommends retesting with a more accurate test.

Lab-processed COVID-19 tests, which detect genetic material from the virus, are generally more accurate. But even these miss some infections, most often because the sample didn't pick up enough of the virus, Pride says. "It could also be that some patients aren't shedding the virus every day, or not shedding it at the exact moment you decide to test," he says.

Because of those uncertainties, you have to consider the results along with other factors, such as your medical history, symptoms, and risk of exposure to COVID-19. Here’s how the CDC has advised acting on results, though this guidance may change depending on the availability of follow-up tests:

If you have symptoms and test positive, you almost certainly have COVID-19. To avoid infecting others, stay home and away from other people for at least 10 days after your symptoms first appear. After that, you can likely be around others as long as you are feeling better and haven’t had a fever in 24 hours—but check with your doctor first.

If you have symptoms and test negative, it’s unclear whether you have COVID-19. Your healthcare provider may test you for other infections and repeat the coronavirus test. If you have two negative tests at least 24 hours apart, it's okay to be around others as long as you are free of fever and symptoms have improved. If a second test is positive or if you are not retested, follow the 10-day rule above to protect others.

If you don’t have symptoms and test positive, it’s likely you’ve been infected with SARS-CoV-2. Even if you don’t develop symptoms, you should stay home for 10 days or until you have two negative tests at least 24 hours apart. If you do get sick, follow the guidelines above to minimize the risk of infecting others.

If you don’t have symptoms and test negative, you probably are not infected. But given that the test can be falsely negative, if you had close contact with someone with COVID-19, you should still stay home for 14 days to limit the risk of infecting others.

To protect yourself and everyone else, once you’re cleared to go out, you should still follow the CDC’s advice to stay home as much as possible and, when you do go out, wear a mask and keep at least 6 feet away from others.

Will Insurance Cover the Cost of Testing?

By law, it's supposed to. Under the Families First Coronavirus Response Act, private insurance, Medicare, and Medicaid are required to cover diagnostic testing for COVID-19 at no out-of-pocket cost to you. Unfortunately, it doesn’t always work this way in practice.

For more on the cost of testing and avoiding a surprise bill, see our guide here