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a lab worker performing a coronavirus test
a lab worker performing a coronavirus test
a lab worker performing a coronavirus test

Coronavirus Test FAQs

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As communities begin to reopen, continued testing for COVID-19 is needed to help control its spread. Lisa Maragakis, senior director of infection prevention, answers common questions about testing.

What are the types of coronavirus tests?

There are two basic types of tests for COVID-19.

Viral or diagnostic test: A viral test can tell you if you are currently infected with the coronavirus that causes COVID-19. This is the test you will receive if your doctor refers you for a COVID-19 test based on your symptoms and other factors.

Early in the pandemic, researchers at Johns Hopkins Medicine developed a screening test that we use, along with other types of viral detection tests, to check for the virus.

Antibody test: An antibody test can show if you were previously exposed to or infected with the virus that causes COVID-19, and if your body has created antibodies in an attempt to defend itself. It takes at least 12 days after exposure for your body to make enough antibodies to show up on a test.

This test helps scientists gather data about how the immune system fights off COVID-19 in recovered patients. We do not yet know if a person with a positive antibody test is protected from getting re-infected with the virus or, if so, how long that protection might last.

Doctor taking a swab sample.

Johns Hopkins Ramps Up COVID-19 Testing to 1,500 a Day

A team of about 90 people work around the clock in the microbiology lab to process as many as 1,500 tests each day — a number that could double as the lab continues to add processing platforms.

Who should get a coronavirus test?

The answer varies based on many factors including a person’s symptoms, exposure history and underlying risk factors for severe disease. 

People Who Have COVID-19 Symptoms:

Everyone with coronavirus symptoms should self-isolate and contact their medical provider or a local center to schedule a test. Many people have mild symptoms, and it will become increasingly difficult to tell whether symptoms are due to COVID-19 once other respiratory viruses such as influenza start to circulate in the fall and winter months. Tests can be helpful to find out if symptoms are due to COVID-19 so you can take precautions to avoid passing the infection to others. Test results can also help to guide your medical care whether you have COVID-19 or another type of respiratory virus.

Talk to your health care provider to find out what he or she recommends. Remember, unless you have life-threatening circumstances that require calling 911 or going to an emergency department, stay home and call your doctor’s office to discuss your symptoms before going to a health care facility or testing site. This helps prevent the spread of the virus.

It’s also important to know that the availability of testing varies by state and local health department. Johns Hopkins Medicine provides tests with a doctor’s referral and, in some cases, for Maryland and Washington, D.C., residents who do not have a referral.

In areas where testing remains in short supply, according to the U.S. Centers for Disease Control and Prevention (CDC), these groups should be given priority to be tested for COVID-19:

  • Hospitalized patients with COVID-19 symptoms.
  • People who work in health care facilities and group residences such as nursing homes.
  • First responders (emergency medicine technicians, police officers, firefighters and others) who have COVID-19 symptoms.
  • People with COVID-19 symptoms who live in long-term care facilities or other group living settings, including prisons and shelters.

The next level of priority goes to those who:

  • Have COVID-19 symptoms such as cough, fever or chills, shortness of breath or difficulty breathing, muscle or body aches, sore throat, new loss of taste or smell, diarrhea, headache, new fatigue, nausea or vomiting, or congestion or runny nose.
  • Are recommended for testing by their doctor or local health department for public health monitoring or other reasons.

People Who Don’t Have COVID-19 Symptoms:

Many health experts believe that more people — including those with no symptoms of the virus — need to be tested to help prevent the virus’s spread. Since availability of testing supplies varies across the country, different federal, state and local agencies may recommend different guidelines.  Johns Hopkins Medicine recommends self-quarantine and testing for people who have had a recent exposure to someone who has COVID-19. Periodic testing is also recommended for asymptomatic individuals living in high-risk congregate settings such as long-term care facilities.

Johns Hopkins Medicine does not conduct routine testing of health care personnel who are not exhibiting symptoms; however, JHM employees without symptoms may be tested at one of the predesignated testing sites, including the Baltimore City Convention Center (BCCC). 

People Who Have Recovered from COVID-19:

In general, people do not need to be tested at the end of a COVID-19 illness. They can stop self-isolating once their doctor advises them it is safe to do so. Generally, factors to consider are:

  • You have had 24 hours without fever (off of anti-fever medication), AND
  • It has been at least 10 days since you first experienced symptoms, AND
  • Your symptoms are improving.

Sometimes, depending upon how severe your illness is and whether your immune system is compromised, your doctor may recommend a longer period of self-isolation. If you want to participate in a research study, having an antibody test after you have recovered can help scientists gather data about how the virus affects people differently and how the immune system responds.

Are you immune after having the coronavirus? Scientists are still trying to understand if antibodies to the virus that causes COVID-19 prevent people from becoming infected again and, if so, how long a person may be immune once they’ve recovered. More data are needed to know when a person should be re-tested if he or she develops symptoms again after recovering from COVID-19.

How is testing done for COVID-19?

Be sure to follow all information and guidance from your health care provider before getting a test. Many testing facilities, including Johns Hopkins Medicine, schedule tests by appointment. It’s also important to follow physical distancing and wear a mask before and after the test takes place.

The health care professional giving you the test will wear protective clothes, a mask and a face shield. He or she will collect samples of your respiratory fluids or saliva.

To collect the sample, the medical team member inserts a swab deep inside your nose and toward the back of your throat. It may be mildly uncomfortable but only takes a few seconds. The samples are then packaged according to CDC guidelines and sent to a laboratory for analysis.

The laboratory tests samples for the presence of the coronavirus (SARS-CoV-2), which causes COVID-19. Either your care provider or the lab will notify you with the results.

Illustrated tablet with multiple choice answer selections

Coronavirus (COVID-19) Self-Checker

Check symptoms. Protect yourself. Get information.

Where can I get a coronavirus test?

In most cases, COVID-19 tests must be ordered by a doctor. The doctor might test you in the office or refer you to a commercial testing center or a testing location set up by your city or town. Johns Hopkins Medicine provides tests at several locations with a doctor’s referral.

Testing varies by state, so talk to your doctor and ask if a COVID-19 test is appropriate for your situation.

The Food and Drug Administration has approved in-home test kits for use under certain circumstances. If you test yourself, you must send your samples to a lab for results. Depending upon the type of test and how the sample is collected, do-it-yourself home tests may be less reliable than tests administered by trained professionals. Some testing sites may provide you with instructions and allow you to collect the sample yourself for testing.

How long does it take to get COVID-19 test results?

Getting coronavirus test results can take anywhere from an hour to several days. Some hospitals, such as Johns Hopkins, have testing labs on site. Other testing sites may need to send the samples away to a lab for analysis. If your test is positive, the results will be reported to you and are also reported to public health authorities.

If your test shows you’ve been infected, your health care practitioner will recommend what you should to do next. Most cases of the illness are mild and can be managed at home, but here is more information about what to expect if you have COVID-19.

If I’ve been tested once, do I need to get tested again?

Getting a negative test result means it is unlikely you were infected with the new coronavirus when your test sample was taken. But if you are tested when you are in the earliest stages of infection, before the virus is detectable, you might still be infected despite having a negative test result. If you are exposed to someone with COVID-19, you should self-quarantine and watch for symptoms to develop in the 14 days following exposure, even if you get a negative test result at some point during this period. Also, even if your test results are negative, you could still catch the coronavirus later and need to be tested again.

If you have symptoms, let your health care provider know if they persist or worsen, and you might be tested again.

Scientist carefully insets a pipette into a test tube.

Coronavirus (COVID-19)

What you need to know from Johns Hopkins Medicine.

Updated October 22, 2020