Can I try on clothes at the store? Your COVID-19 questions answered

We're breaking down what you need to know about the pandemic by answering your questions. You can send us your questions via email at COVID@cbc.ca and we'll answer as many as we can. We'll publish a selection of answers every weekday on our website, and we're also putting some of your questions to the experts on the air during The National and News Network.

So far, we've received more than 35,000 emails from all corners of the country. Your questions have surprised us, stumped us and got us thinking.

Can I try on clothes at the store?

As more businesses reopen throughout the country, people are wondering how this will apply to retail stores. Pat H. is curious if trying on clothing will be safe.

While we don't have a definitive answer to Pat's question, we spoke to a couple of infectious diseases specialists who helped us understand the risks of retail shopping.

"People who want to try on clothes in a store should follow general principles intended to reduce the risk of exposure," says Dr. Matthew Oughton, infectious diseases specialist at the Jewish General Hospital in Montreal and assistant professor at McGill University.

This includes not trying on clothing if you are sick or have COVID-19 symptoms, following all store policies in place, using good hand hygiene before and after trying on clothing. Oughton also says you could consider washing your clothing in a washing machine after purchase.

Dr. Lisa Barrett, infectious disease specialist and assistant professor at Dalhousie University, agrees.

"If you wash your hands and don't touch your face, it is very unlikely you would get the virus from clothes."

We also know the virus can remain infectious on different surfaces for varying amounts of time. So how does it behave on clothing? Oughton says it seems the virus is "less viable" on absorbent surfaces like cloth as opposed to "surfaces that are hard and non-porous."

According to the World Health Organization, the disease spreads primarily through tiny droplets expelled when a person infected with SARS-CoV-2 sneezes, coughs, exhales or spits while talking. In order to curb the spread, Oughton says the emphasis should be on ensuring physical distancing and good hand hygiene within the store.

"If I have had to pick two things for stores to do to keep their staff and clientele the most safe, it's still the same two things we've been telling the general population, which is really good hand hygiene … the second thing is physical distancing," he says.

But remember, the reopening of businesses is a good sign.

"The reason that things are opening up (in most places other than Quebec) is that the amount of virus in the community in general is starting to decrease," says Barrett. "So your chances of encountering the virus are generally starting to decrease."

Will a COVID-19 vaccine need to be administered yearly or just once?

We are receiving a lot of questions about the race for a vaccine. Cate B. is wondering how long a potential COVID-19 vaccine could last, and whether it's something we'll have to get every year like the flu shot.

Dr. Michael Curry, a University of B.C. professor and emergency physician, says the answer to Cate's questions depends on how quickly the novel coronavirus mutates, adding that influenza vaccines protect against particular strains of the virus, but only until it changes into something else.

"But [the coronavirus] evolves more slowly than the flu, which would suggest an immunization for COVID-19 will probably provide slightly longer protection than we would get from a flu shot," says Curry.

Matthew Miller, an infectious diseases expert at McMaster University, suspects that once a vaccine is developed for the coronavirus it will need updating, but probably not every year.

"You know it's hard to guess on the time frame but maybe something like every five to 10 years," says Miller.

But until we have a COVID-19 vaccine, it is difficult to predict how long it could last.

Will there be a second wave of COVID-19, and how bad it could be?

Donald G. is wondering whether there will be a second wave of COVID-19.

"We know with great certainty that there will be a second wave — the majority of scientists [are] sure of that. And many also assume that there will be a third wave," Lothar Wieler, the head of Germany's national disease control centre, said Tuesday.

A second wave of the outbreak is defined as an increase in infections that occurs after a sustained period of time when there are no—or very few—new cases of that illness, said Dr. Isaac Bogoch, infectious diseases specialist at Toronto General Hospital.

Whether that happens is dependent on how Canadians "gradually shift that dial or that dimmer switch toward fewer and fewer public health restrictions," said Bogoch.

"But if people are clustering together, and if we see pockets of infection, and these pockets are spreading to other places, we might see a second lockdown," he warned.

Other countries have seen second waves of COVID-19, after relaxing of their social distancing rules, said respirologist Dr. Samir Gupta. "So that's really on us to decide.

If a second wave of the outbreak does happen in the fall, Gupta says it would coincide with the conventional flu season in Canada.

That said, if we continue maintaining "the good habits" we're following right now, like washing our hands, physically distancing to some extent and being careful about not going out if we're sick, Gupta says we might actually see a mitigation in the severity of spikes during the flu season.

Why is two metres the recommended distance for preventing transmission?

Rick G. is wondering whether the two metre rule is far enough away to stop the virus from landing on him, when he's out shopping for essentials.

Our colleagues at Second Opinion tackled this topic in the latest edition of their CBC News health newsletter.

In 1934, W.F. Wells at the Harvard School of Public Health showed that large droplets (bigger than 0.1 millimetre) tended to fall and settle on the ground within a distance of two metres, while smaller droplets evaporated and the virus particles left behind could remain suspended in the air for a long time.

He proposed that could explain how diseases are transmitted.

Since then, respiratory diseases have been divided into two groups; those illness that are transmitted via droplets (usually from close contact), and illnesses that are airborne and can spread over longer distances, such as measles or tuberculosis.

Such tiny particles are presumably pushed around by air currents, but can't move easily due to air resistance. So their actual movements haven't been well modelled or measured, said Lydia Bourouiba, professor and director of the Fluid Dynamics of Disease Transmission Laboratory at the Massachusetts Institute of Technology.

"And that's why the notion of airborne [transmission] is very murky," said Bourouiba, who is Canadian.

Some studies, including Bourouiba's, suggest that droplets from coughs and sneezes can, in fact, travel much farther than expected. Bourouiba's high-speed imaging measurements and modelling show smaller respiratory droplets don't behave like individual droplets but are in a turbulent gas cloud trapping them and carrying them forward within it.

So what does that say about the two-metre guideline?

Bourouiba says her research points to the potential for exposure beyond two metres from someone who is coughing and sneezing. As she wrote in the journal JAMA Insights in March, that means it's "vitally important" for health care workers to wear high-grade personal protective equipment in the form of respirators even if they're farther than two metres from infected patients.

However, she does think two metres can be far enough for healthy people in the general public in most environments, since breathing and talking don't propel droplets and surrounding cloud too far.

We're also answering your questions every night on The National. Last night, your questions included, how long until non-essential workers can go back to work? Watch below:

Wednesday we answered questions about dental appointments and PPE disposal. Read here.

Keep your questions coming by emailing us at COVID@cbc.ca.