How risky is it to go shopping now? Your coronavirus questions answered

We're answering your questions about the pandemic. Send yours to COVID@cbc.ca, and we'll answer as many as we can. We publish a selection of answers online and also put some questions to the experts during The National and on CBC News Network. So far, we've received more than 57,300 emails from all corners of the country.

How safe is it to go shopping?

With the holidays on the horizon and Black Friday promotions out in full force, readers like Sue G. are asking if it's still safe to go shopping.

First, it's important to note public health authorities are urging people to stay home as much as possible by limiting errands and outings to just the essentials.

So, if you have to buy something, the Public Health Agency of Canada (PHAC) is advising that you reduce your risk of exposure by making purchases online or using curbside pickup when possible.

In fact, these may be the only options in some parts of the country, such as Manitoba or parts of Ontario, where non-essential retail has been temporarily restricted.

But if the stores are open where you live, does that mean it's safe?

Despite Canadian chains, including Loblaw and Sobeys, reporting numerous positive cases throughout the pandemic, experts have said there is no evidence that grocery shopping has led to significant outbreaks or transmission.

That said, shopping is not without risk.

"I would not spend any more time than necessary at an indoor mall or store," said epidemiologist Lisa Lee, a professor at Virginia Tech in Blacksburg, Va., and a former official at the Center for Disease Control and Prevention in the United States.

"Steer clear from anyone without a mask, and do not spend more than 15 minutes near others," she said in an email to CBC News.

PHAC is also advising that Canadians avoid close-contact situations where they can't keep two metres apart from other people, as well as skipping crowded places and closed spaces with poor ventilation.

So are smaller stores with fewer people safer than larger ones?

Not really, said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, who studies how viruses are transmitted in the air.

"In the larger stores, the risk is lower because people can be more spaced out in there," Marr said. "Larger, more modern buildings tend to have better ventilation systems."

Retailers are also doing their part to mitigate risks.

Michael LeBlanc, a senior retail advisor at the Retail Council of Canada, said people should plan ahead so they don't spend any more time than necessary when shopping.

Some retailers have made a conscious effort to stretch out sale periods so consumers aren't compelled to all go at the same time.

"Keep your distance, be patient, wear your mask, be cool, be calm," LeBlanc said.

"We don't want retail to be this social gathering place where everybody hangs out."

Is it safe for seniors to walk in the mall?

Some of our other readers also want to know if it's safe to go to the mall but not necessarily for shopping.

Wendy M. asked if it's OK for seniors to get their exercise walking in the mall as the weather gets colder.

While all of the experts we spoke to agree that it's important to exercise and stay healthy during the pandemic, they are split on whether or not the mall is the right place for seniors to take their winter walks.

"For a person who is at high risk of serious complications, they should exercise, yes, but only when crowds are very sparse," said Dr. Colin Furness, an infection control epidemiologist and assistant professor at the University of Toronto's faculty of information. "A really big mall with high ceilings that isn't crowded won't be especially dangerous."

Adrian Wagg, a professor of healthy aging at the University of Alberta in Edmonton, agrees that walking in the mall is not a risk as long as you stay more than two metres apart from others, wash your hands regularly and wear your mask.

However, Dr. Anand Kumar, an associate professor in the department of medical microbiology at the University of Manitoba in Winnipeg, said he would recommend seniors try to workout at home or outdoors instead.

"Exercise substantially increases the amount of air you exhale and inhale per minute," he said. "It's been shown that exercise is one of the high-risk situations, especially if you are in an enclosed space."

Is there a safe way to get together?

While Christmas isn't cancelled this year, experts say it should be done differently, with large, extended family gatherings likely off the table.

Corrine B. wanted to know if there were any strategies for making gatherings safer indoors.

First, it's important to check what your local public health guidelines allow. Indoor gatherings are being discouraged in most places across the country. In Manitoba and some regions of Ontario, they're not allowed at all.

But if gatherings are allowed where you live, the experts said there are some things you can do to minimize the risk.

"There is no such thing as a perfect risk-free alternative," said Dr. Matthew Oughton, attending physician in the division of infectious diseases at the Jewish General Hospital in Montreal. "This is all about reducing risk as much as possible."

The virus spreads when people are in close contact with one another and those who are older or have underlying medical conditions tend to have worse outcomes when infected by the virus, Oughton said.

He suggested taking the following steps to make gatherings safer in your home.

• Have guests distance within your home.

• Provide ample access to supplies for good hand hygiene.

• Avoid hugging and close contact.

• Avoid singing (even Christmas carols).

• Don't share food or drinks.

In a previous article, medical experts also warned that the risk of getting the virus increases when you spend longer periods of time in close contact with others.

And while raising a toast may be a holiday tradition, it's a good idea to limit how much alcohol guests drink, Oughton said.

"Alcohol lowers inhibitions and during a pandemic, unfortunately, it's inhibitions that in part are helping to keep people safe," he said.

Wearing masks and opening windows can also help, but improving air circulation doesn't replace the need to keep your distance from other people, Oughton said in an earlier article.

And if you can hack it, you may want to consider meeting outdoors if your local public health guidelines permit it. Research shows the risk of transmission is lower outside, likely due to better ventilation and because it's easier to physically distance.

What about a small dinner in my garage?

With winter weather making outdoor gatherings a lot less appealing, Susan M. wrote to ask if it was safe to have guests over in her garage.

"If you're just comparing being in a garage with an open door versus being indoors without any windows open — certainly being in an area where there is more and better ventilation is better," said Dr. Alon Vaisman, an infectious diseases and infection control physician with the University Health Network in Toronto.

Aerosol expert Marr agrees. But she would "still have people be masked and distanced."

Vaisman said that even with garage doors and windows open, they are "not necessarily safe."

If you follow local public health guidelines in most parts of the country they would advise you not to visit other people's homes or garages, Vaisman said.

Doesn't the cold weather kill the virus?

The answer is no.

In fact, Marr cautioned that the opposite is true — viruses survive longer in colder, drier environments whether they're in the air or on surfaces.

She also identified recirculated air in heated homes and buildings as a potential risk.

"This leads to greater potential for a virus to build up in the air and for people then to be exposed to higher levels of it," Marr said.

Experts said dry air can also make our bodies more vulnerable to pathogens, like the virus that causes COVID-19, by drying out the protective mucous membrane that lines our respiratory tracts.

Dr. Zain Chagla, an infectious disease physician at St. Joseph's Healthcare Hamilton and an associate professor of medicine at McMaster University, pointed to another issue that impacts how we cope with COVID-19 in the winter — our behaviour.

"There's a reason why we see respiratory viruses in the winter in Canada," he said. "We tend to be more indoors, more gathered [in] more poorly ventilated settings."

So what should we do? Invest in some good, warm winter clothing, Chagla said.

"We're going to have a long winter and the outdoors is still a viable option for people to meet," he said.

"The risk is so low — it isn't zero — but it's modified," Chagla said.

As long as it's permitted to meet outside, it's a good option, he said. Even short outdoor meetings can provide a much-needed boost.

"Having 15 minutes of real life interaction is just so precious for people."

How safe is it to fly?

Despite the government's travel advisory, we're hearing from a number of Canadians looking to head south this winter.

Ursula H. said she's Florida-bound and wanted to know how safe it was to get on a plane right now.

When it comes to transmission of the virus, experts say airplanes are actually quite safe.

Canada's Chief Public Health Officer Dr. Theresa Tam said earlier this month that there was little evidence that COVID-19 was being transmitted by passengers on airplanes, even though the Public Health Agency of Canada was aware of reports that infected people had travelled into the country by air.

"There have been very few reports, extremely rare reports, actually, of transmission aboard aircraft," Tam said. "Very, very little."

In fact, a Harvard University study found that flying may actually be safer than other routine activities, such as grocery shopping, because of "layered" prevention measures, such as air filtration systems, mask policies, frequent cabin cleaning and screening for symptomatic passengers.

Another study conducted by the U.S. Department of Defence also found ventilation systems and stringent masking policies have made onboard transmission rare.

Chagla said an airplane's ventilation system is pretty similar to those used in operating rooms, but being on board isn't the riskiest part of flying.

He pointed to everything leading up to and after the flight, such as taking transit to the airport and waiting in line, as opportunities for transmission.

"All of that probably presents a higher risk than the flight itself," Chagla said.

Can vitamin D protect me from COVID-19?

If you're not racing for warming temperatures, some readers have been wondering if they should be heading to the pharmacy to buy vitamin D supplements.

But do they actually help?

The answer is probably not, according to Dr. Christopher Labos, a cardiologist at Notre Dame Hospital in Montreal.

"To date, there is no research showing that taking a vitamin tablet will prevent or help cure [the] coronavirus," Labos said.

When it comes to vitamin D specifically, Dr. Isaac Bogoch, an infectious disease specialist and researcher based at Toronto General Hospital, noted that there were some "poorly constructed studies" that said it might help, but that the research fell apart on closer examination.

Labos said some studies have shown people with low levels of vitamin D tend to have worse outcomes after having contracted COVID-19, but he warned against drawing the wrong conclusions.

It's not that the low vitamin D levels cause disease or cause COVID-19, but that older people or people with pre-existing medical conditions tend to have low vitamin D levels, he said.

So while it's unlikely that taking a supplement will help prevent you from contracting, or fighting COVID-19, should you take it anyway? Not necessarily.

Statistics Canada says about two-thirds of Canadians already get enough vitamin D from natural sources or supplements.

Dr. Todd Alexander, a pediatrician and professor at the University of Alberta, said you probably don't need to be taking supplemental vitamin D, and that in fact, it might have adverse effects.

"You're getting plenty, and in my opinion, the risks would outweigh the benefits."

The risks of taking too much vitamin D can vary depending on your health and age.

In children, for example, too much vitamin D can cause a buildup of calcium in the blood, which can lead to kidney stones, said Alexander.

So you should always ask your doctor whether supplementing with vitamin D is right for you.