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How Reliable Are COVID-19 Tests? Dr. Mallika Marshall Answers Your Coronavirus Questions

BOSTON (CBS) -- As the number of coronavirus cases continues to grow, we are receiving a number of questions from the public. Dr. Mallika Marshall answered some of the questions sent to WBZ-TV's Facebook, Instagram, and Twitter accounts.

Why can't everyone get tested? Why the need to wait for symptoms? I think you can track it better. -Joey, Facebook

You're absolutely right, Joey. In order to figure out who has it and who doesn't, we need to do more widespread testing. Unfortunately, we still don't have enough tests to do that. We're getting more each week and slowly relaxing the testing guidelines, but right now we don't have the ability to even test all of the people with symptoms, much less those without.

How reliable are the COVID-19 tests? -Susan

Some experts believe that up to 30% of people who actually have the infection will have a negative test. One reason is that the swab has to get deep into the nasal cavity to get a good sample and if not done correctly you may get a false negative. So many doctors are continuing to assume that patients with typical symptoms have COVID-19 even if the initial swab is negative.

How quickly does hand sanitizer kill the coronavirus? -Marisol 

I spoke to an Infectious Disease specialist at Mass. General and she said the key is to make sure the sanitizer completely dries on your hand before you can trust that the virus has been neutralized. So after a squirt, rub your hands together thoroughly until your hands are dry before touching anything else.

When I walk past someone wearing perfume, even at seven to 10 feet away, I can smell the scent in the air. Why is it that the scent travels further than six feet in the air, but the virus droplets supposedly don't? -Ric 

Larger droplets like from a cough or sneeze do tend to settle onto surfaces rather than linger in the air. There has been some debate about whether smaller droplets can float in the air and even if they do, whether someone can become infected from them. You may have heard about a recent CDC study that found droplets may be able to travel up to 13 feet. Another good reason to stay as far away from others as possible.

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