By Dr. Mallika Marshall

BOSTON (CBS) – Dr. Mallika Marshall is answering your coronavirus-related medical questions. If you have a question for Dr. Mallika, email her or message her on Facebook or Twitter.

Dr. Mallika is offering her best advice, but as always, consult your personal doctor before making any decisions about your personal health.

READ MORE: Acadia National Park In Maine On Track For A Record Year

How long should I wait to drive my car after it was road-tested by a tech not wearing a mask? – Matt

To be on the safe side, I would just let it air out by opening the windows or doors and then wiping off the seat, steering wheel, and console with disinfectant.

Do we still have to wipe our groceries off and leave our mail alone for a day or two? – Diane

READ MORE: Bill To Scrap MCAS Test Is Subject Of Virtual Public Hearing

You probably don’t need to compulsively wipe off your groceries or let packages sit unopened for days anymore. The CDC says you’re much more likely to catch the virus from person-to-person contact than from food packaging or mail. But it’s still a good idea to wash your hands well after you’ve handled your groceries or opened your mail.

I have stage 3 kidney disease. Does that put me at higher risk for COVID? – Erica from Milford

Yes, people with kidney disease are more likely to develop COVID-related complications if they contract the virus so it’s important that you take special precautions to stay healthy by keeping your distance from others, wearing a mask out in public, and washing your hand frequently.

If I find out I was exposed to somebody with COVID-19, how long should I wait before getting tested? I don’t want to risk a false negative. – Julie

MORE NEWS: Keller @ Large: Mayoral Candidate Michelle Wu Says Boston 'Can't Afford To Just Nibble Around The Edges Of The Status Quo'

According to Harvard Health Publishing, if you get tested on the day you are exposed to the virus, there’s a 100% chance you will get a false negative. That’s because there aren’t enough viral particles in the back of your nose to be detected by the swab test. Four days after exposure, that false-negative rate drops to 40%. But even if you have symptoms for a few days, you still could get a false-negative test 20% of the time. This is why it’s so important that if you have been exposed to someone with COVID and test negative, you still should self-isolate for 14 days.

Dr. Mallika Marshall