TORONTO -- The scientific race to understand, control and, hopefully, eradicate the novel coronavirus has been underway for months.

Canada has emerged from lockdown and returned to at least a semblance of normalcy that will soon include a large-scale return to school of elementary and secondary students.

The curve of the country’s total number of confirmed cases of COVID-19 has flattened, now reaching more than 126,000 as of Aug. 27, but questions remain about how and how quickly the virus spreads, who’s at risk, how people can protect themselves and how transmission can be managed going forward.

To sort through some of the noise, CTVNews.ca asked several doctors to address some of the most frequently asked questions about the ongoing pandemic.

Can you contract COVID-19 more than once?

Scientists at the University of Hong Kong said on Aug. 24 that they have the first evidence of someone being reinfected with the virus that causes COVID-19.

Genetic tests revealed that a 33-year-old man returning to Hong Kong from a trip to Spain in mid-August had a different strain of the coronavirus than the one he'd previously been infected with in March, said Dr. Kelvin Kai-Wang To, the microbiologist who led the work.

The man had mild symptoms the first time and none the second time. His more recent infection was detected through screening and testing at the Hong Kong airport.

Kai-Wang To said the man’s case shows that some people don’t have “lifelong immunity” to the virus after having it once.

The paper has been accepted by the journal Clinical Infectious Diseases but not yet published, and some independent experts urged caution until full results are available.

Whether people who have had COVID-19 are immune to new infections and for how long are key questions that have implications for vaccine development and decisions about returning to work, school and social activities.

Even if someone can be infected a second time, it's not known if they have some protection against serious illness, because the immune system generally remembers how to make antibodies against a virus it's seen before.

Early on in the pandemic, there were 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.

Dr. Iris Gorfinkel, a Toronto family physician and medical researcher, told CTV’s Your Morning on March 16 that’s it’s difficult to pin down immunity because viruses tend to morph.

“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.

Infectious disease specialist Dr. Abdu Sharkawy said it’s “quite possible” for individuals who had COVID-19 to become infected again.

“One of the concerns we have is there may be a second wave of infection if our strategies for containment and for infection control are not good enough, and that's why it's really important for everybody to adopt a very consistent attitude and philosophy that we're in this for the long haul,” he told CTV’s Chief News Anchor and Senior Editor Lisa LaFlamme.

On April 11, the World Health Organization (WHO) told multiple media outlets they were investigating reports of recovered COVID-19 patients testing positive for the illness again after they initially tested negative.

However, the WHO said they still need more epidemiological data to draw any conclusions about the virus’ “shedding profile.”

Is a second wave of infections coming?

Britain, Germany, France, South Korea and Rwanda are among the countries tightening up pandemic restrictions in the face of rising numbers. In Europe, the increase in cases is being blamed on summer travel and gatherings of friends and family.

COVID-19 has killed more than 826,000 people worldwide since surfacing in China late last year and more than 24 million infections have been recorded. But health authorities around the world have repeatedly warned that this pandemic could come in waves, just as the Spanish flu in 1918-1920 did.

The outbreak began in March of 1918 and a second wave, far deadlier than the first, hit in the fall of 1918. The pandemic then subsided for almost a year and resurged again in the fall and winter of 1919.

Many public health experts warn that with a return to indoor living as the cool weather of the fall descends, a spike in cases is very likely. There is also the threat of trying to manage COVID-19 cases during the traditional flu season, a twin-epidemic spectre that health experts warn could overwhelm health-care systems.

But the end of winter in the Southern Hemisphere is cause for some optimism. Countries there, including South Africa, Australia and Argentina, saw lower-than-normal flu numbers. In some areas, there was virtually no flu at all. It’s believed that masking, physical distancing, better hand hygiene, and crowd avoidance helped to minimize the spread of both the flu and COVID-19.

"This could be one of the worst seasons we've had from a public health perspective with COVID and flu coming together. But it also could be one of the best flu seasons we've had," Dr. Robert Redfield, director of the U.S. Centers for Disease Control and Prevention, told The Associated Press on Aug. 26.

Getting the flu shot will provide no protection against COVID-19, says Dr. Isaac Bogoch, an infectious diseases specialist in Toronto, but regular vaccinations are still important for optimizing health.

“We should be up to date on all our routine vaccinations, our pneumonia vaccines, our flu vaccines, our regular vaccines, so that we can ensure that our health is optimized in case we come down with an infection,” he said.

That’s important in warding off the scenario of having both COVID-19 and a strain of the flu or another virus simultaneously.

“It’s totally possible to have what’s called a co-infection and we know people who have multiple infections at the same time can have a worse outcome,” Bogoch said.

How far away is a vaccine?

Some pharmaceutical giants have said a vaccine could be on the 2020 horizon, but other experts say it may be unrealistic to even expect one in 2021.

What is clear is that there are hundreds of potential vaccines in development – some already in human clinical trials – and governments around the world have invested billions in vaccine research.

Check out CTVNews.ca’s vaccine tracker to learn more.

And while the world awaits a vaccine, there are continuing advances in treatments, surveillance, and testing that experts say will help mitigate the spread and effects of the virus.

How do you know if you have a cold, the flu, or COVID-19?

Those who are infected with COVID-19 may have few to no symptoms, according to the Public Health Agency of Canada (PHAC). If symptoms are present, they can easily be mistaken for a common cold or the flu because of their similarities.

According to the health agency, the most common symptoms of COVID-19 are fever (38 C and above), new or worsening cough, difficulty breathing, chills, fatigue or weakness, muscle or body aches, headache and gastrointestinal issues, including vomiting, diarrhea and pain.

Children have been more commonly reported to have abdominal symptoms, and skin changes or rashes, says the PHAC.

The World Health Organization says the most common symptoms are fever, dry cough, and tiredness. Less common symptoms, it says, include aches and pains, nasal congestion, headache, conjunctivitis (pink eye), sore throat, diarrhea, loss of taste or smell or a rash on skin or discoloration of fingers or toes.

Gorfinkel said clinicians can’t distinguish between the illnesses based on symptoms alone. She said they can all present the same way, which is why the patient’s travel history or history of exposure to the virus is so important in determining whether someone might have COVID-19.

“We do not have the facilities or the tests to test absolutely everybody, so that history of travel if you’re basically otherwise well, that’s a critical part of it,” she explained.

Is losing your sense of smell or taste a sign of a minor case of COVID-19?

Both the Public Health Agency of Canada and the World Health Organization have added the loss of sense of smell and/or taste to their lists of symptoms.

There have been reports of COVID-19 patients who lost their sense of smell and/or sense of taste, but they didn’t show any other symptoms of the disease.

Because research on the topic is still in its early stages, Bogoch said those symptoms alone are not enough to indicate someone has COVID-19.

“We don’t have all the answers yet,” he told CTV’s Your Morning on April 16. “But we're hearing more and more people who have disturbances in taste and smell and there's even some data that's emerging that says maybe about 25 to 30 per cent of people might have that, along with some other symptoms.”

Bogoch said it’s also important to remember that the loss of sense of smell and taste are common symptoms of many other upper respiratory viral infections.

“It’s not specific to COVID-19, but it certainly may be a component of this infection,” he said.

Who is getting tested?

According to the latest data from the PHAC, as of Aug. 26, more than 5,246,341 people have been tested for COVID-19 in Canada. This corresponds to a test rate of 139,570 per one million people. Of all people tested, 2.3 per cent have been found to be positive.

Canada does not have formal criteria for determining who should be tested, meaning guidelines vary from province to province. In Alberta, for instance, anyone can be tested, regardless of whether they have symptoms.

Ontario and B.C., on the other hand, are only testing those with symptoms.

Anyone who is showing symptoms of COVID-19 or is concerned they may have acquired the virus should contact their doctor or other primary health-care provider.

Can young people fall seriously ill?

While much of the attention about who is most vulnerable to COVID-19 has centred on the elderly and those with underlying medical conditions, cases among young people are growing.

According to the latest PHAC data, as of Aug. 26, the 20 to 29 cohort made up the largest group by percentage of total confirmed cases at 15.7 per cent. Those 80 and above were the second largest cohort at 15.2 per cent.

Those 19 and under made up 8.5 per cent of total cases.

The data shows 68.4 per cent of Canada’s cases were among those under the age of 60, while those under the age of 50 made up 53.7 per cent of the total.

Those percentages among younger demographics have creeped up as the pandemic has gone on. As of April 15, COVID-19 patients under the age of 60 made up 65 per cent of Canada’s total cases, while those under the age of 50 made up 47 per cent of the total.

Bogoch said that everyone can be infected by the novel coronavirus and there’s always a risk that some people will have a more severe infection.

However, he said older people and those with underlying medical conditions still have a greater risk of a severe outcome than younger individuals.

“If we take a step back and look at the 30,000-foot view and look at who is more likely to get a severe infection, it is overwhelmingly those over the age of 60 and really, over the age of 80 years old,” he told CTV’s Your Morning on March 20.

As of Aug. 26, 83.5 per cent of those hospitalized for COVID-19 were over 50. Among those who have died, 89.6 per cent were over 70 years old and less than 1 per cent were under 50.

Bogoch said the most important metric to look at when studying data about severe infections from this virus is death.

“If you get infected, you either live or you die, it sounds morbid, but I think that’s an extremely important distinction to make and if we look at death, it is overwhelmingly in those over 60 and disproportionately high in those over the age of 80,” he said.

Is it safe to gather with family and friends in small groups?

Physical distancing recommendations have evolved as Canada has reopened its economy and public life. Early on, health and political leaders urged Canadians to stay home and to only venture out for essentials. They strongly advised against making physical contact with friends or family.

But as the country managed to flatten the curve on new cases, many provinces implemented so-called “bubbles” to govern safe social circles in which households limit their close contact to a defined group of people. That number varies across Canada – from 10 in Ontario to 15 in Alberta, while some provinces, such as New Brunswick, advised no more than two-household bubbles.

"Physical distancing is proven to be one of the most effective ways to reduce the spread of illness during an outbreak," PHAC says on its website.

It lists social activities from least risky to most risky in this way:

• Home alone or with household contacts

• Outdoors with housemates or social bubble

• Outdoors with physical distancing

• Outdoor/indoor short amount of time

• Indoors large groups long time

• Indoors/outdoors crowded longer time

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 droplets generated when an infected person coughs, sneezes, or speaks" instead of through the air.

How long can the novel coronavirus survive on different surfaces?

However, a study from the U.S. National Institutes of Health and published in the “New England Journal of Medicine” 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.

Bogoch 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 March 18.

If you have been in isolation because one person in your household is sick, do you have to continue to stay home for another two weeks if another person falls ill?

For people living in households with multiple residents, it may be difficult to avoid infecting each other. Bogoch says that if someone becomes sick with COVID-19, the best course of action is to call the local public health authority.

“It’s extremely important to call the local public health hotline to discuss the exact situation so they can give you very specific recommendations based on your unique setting,” he told CTV’s Your Morning.

In general, though, it appears the answer to that question may be a 'yes.' PHAC says that anyone who has been in contact with a suspected, probably or confirmed case of COVID-19 should self-isolate for 14 days, starting at the time of contact.

This approach was taken by Prime Minister Justin Trudeau, who entered self-isolation with his family after Sophie Gregoire Trudeau tested positive for the virus. Once his wife was given the all clear, the prime minister remained in isolation until it had been two weeks since their last contact before he went out in public again.

Can you contract the virus from passing people on the sidewalk?

While health officials have warned people to keep two metres apart from each other at all times to avoid spreading the virus, that’s not always possible in certain circumstances, such as in a narrow hallway or on the sidewalk.

Mandatory masks policies in indoor settings and advice to wear face coverings in any situation where two metres’ distance can’t be maintained are now commonplace across Canada.

Bogoch said that obviously people should try to avoid being among crowds in confined places, but there is a very low risk of transmission if it happens.

“The risk of transmission for that second where people are passing within a two-metre radius of each other is almost zero per cent,” he told CTV’s Your Morning on April 16. “It's extraordinarily small.”

Even if one person is infected with COVID-19, Bogoch said it’s “extraordinarily unlikely” they will transmit it to someone passing them on the sidewalk.

The exception, of course, is if they touch each other, he said.

Should seniors and children be separated if they live in the same home?

While children appear to be less affected by the virus, elderly people and those with other medical issues are more at risk of suffering a severe outcome from a COVID-19 infection.

For families that have both seniors and young children living under the same roof, Bogoch said they should take care to separate them if anyone shows symptoms. However, he said that should be the case for anyone who is living with others and exhibits any symptoms, such as fever, coughing, and difficulty breathing.

“You just have to be very mindful if anyone has any symptoms whatsoever they should be separated,” he said.

How can caregivers protect themselves while helping someone with COVID-19 at home?

For people who are caring for a person who has been diagnosed with COVID-19, the Public Health Agency of Canada has a number of tips on how they can protect themselves while they provide care.

According to PHAC, only one healthy person should provide care to the individual with COVID-19, and that person should limit their contact with them as much as possible. They should also not share personal items with them, such as toothbrushes, towels, bed linen, utensils or electronic devices. The ill person should have their own bathroom, if possible. If not, they should put the toilet lid down every time before flushing.

Caregivers should wear a mask, disposable gloves, and eye protection when they’re in close proximity to the patient and never reuse the mask or gloves. They should also frequently wash their hands with soap and water, especially after contact with the sick individual.

What’s more, caregivers should remain vigilant about monitoring themselves for symptoms for 14 days.

Should you wipe down all of your groceries when you return from the store?

While the SARS-CoV-2 virus can linger on surfaces from anywhere to a couple of hours to a few days, Bogoch said it’s not necessary to wipe down groceries after buying them at the store.

“I think if people go to the grocery store, they get groceries, I think it’s just fair to put them away,” he told CTV’s Your Morning.

As for fruits and vegetables, Bogoch said there is no need to take any extra precautions with those and people can simply wash them with tap water before eating them, as they normally should.