Should you wipe down your groceries? Answers to that and other questions.

TORONTO -- As Canada’s total number of confirmed cases of COVID-19 increases, health-care professionals are being inundated with questions about how the virus spreads, who’s at risk, and how people can protect themselves.

To sort through some of the noise, several doctors answered some of the most frequently asked questions about the ongoing pandemic.

Can the virus linger on surfaces or be transmitted through the air?

While the research is still in its early stages, the World Health Organization (WHO) says that preliminary evidence suggests the new coronavirus can persist on surfaces for a few hours or up to several days, but this might vary depending on conditions, such as the type of surface, humidity, and the environment.

As for whether the virus can be transmitted through the air, the WHO states that “the virus that causes COVID-19 is mainly transmitted through contact with respiratory droplets rather than through the air.”

However, a new study from the U.S. National Institutes of Health and published in the “New England Journal of Medicine” has found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19, was detectable in aerosols for up to three hours. The researchers discovered this by using a device to dispense an aerosol with duplicated microscopic droplets of the virus, which would be released by a cough or sneeze. The tests showed the virus in aerosols could still infect people for at least three hours.

The study also found the virus was viable, or contagious, for varying amounts of time on different surfaces. For copper it was viable for up to four hours, up to 24 hours on cardboard, and up to two to three days on plastic and stainless steel.

Dr. Isaac Bogoch, an infectious diseases specialist, said the study provided doctors with helpful guidance on the matter.

This really just reinforces what we’ve been saying all along, ‘wash your hands, wash your hands, wash your hands,’” he told CTV’s Your Morning on Wednesday. 

Can you contract COVID-19 more than once?

There have been media reports in China, Japan, and South Korea about individuals who had the virus and eventually tested negative for it and were released, only to test positive for it again a short time later.

Scientists in those countries have speculated that testing errors could be to blame, either for a false negative that said the patients were free of the virus or for the positive result that signalled its reoccurrence.

Dr. Iris Gorfinkel, a family physician and medical researcher, said it’s really too soon to know whether an individual can contract COVID-19 more than once, and how quickly that can happen.

We actually don’t know. We don’t know how long-lasting the immunity is to it,” she told CTV’s Your Morning on Monday. “These viruses have the tendency to morph and change.”

In fact, it’s still not even clear if people develop an immediate immunity to COVID-19, as is typically the case with other virus strains, such as the flu.

“So just like any other virus, there’s the possibility that it could shift or drift. Just minor changes could change it from a once mild infection to a more severe infection,” she explained.