Can you catch COVID-19 twice? What we still don’t know about the novel coronavirus

After months of battling the novel coronavirus, a lot is still unknown — how it spreads, its symptoms and more — and it continues to kill Canadians everyday.

That’s why researchers like Dr. Matthew Cheng, a professor of medicine at McGill University in Montreal, have been working hard to find out as much as possible about COVID-19.

READ MORE: Family gathering leads to at least 15 COVID-19 cases in B.C.

“We’re learning new information every day,” Cheng told Global News.

Below, Cheng and other experts explain what we know — and what we’re still trying to figure out — about COVID-19.

How many people in Canada have actually been infected with COVID-19?

Global News has a coronavirus tracker which is updated every time a province or territory announces new case numbers for that jurisdiction.

However, these numbers do not reflect the total number of cases in COVID-19 because “not everyone with the virus develops symptoms, and even if they did, not every case is serious enough to warrant testing or hospitalization,” Cheng said.

This presents a number of problems for not only tracking the virus, but also for preventing the spread of the virus and making decisions about reopening various parts of the economy.

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“This is critical information to guide current and future public health policy, because we know that the proportion of individuals who are susceptible is a major factor in our calculations for reopening the country,” Cheng said.

If it’s true that having previously had the virus provides a person some level of protection, it would really help the government to know where those people are in making safe decisions about reopening.

Are children less likely to catch the virus than adults?

There have been fewer cases of the novel coronavirus in children than in adults, Cheng said.

“We do know that all children seem to be at a lower risk of infection, and that’s despite the fact that if and when they become infected, they seem to show the same quantity of virus in respiratory specimens as adults,” he explained.

“The second thing we know is that if they are infected, they seem to have a dramatically less risk of adverse health effects, compared to adults.”

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Coronavirus outbreak: WHO releases scientific brief on links between multisystem inflammatory syndrome and COVID-19

The exact reasons are unclear, Cheng said, but it could have to do with the fact that adults are, on average, more likely to have other medical issues.

“Things like hypertension (and) cardiovascular disease may predispose them to worse outcomes,” Cheng said.

“We do know that age alone seems to be a factor, (but) we’re not exactly sure why that is.”

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This is all part of Cheng’s research. He’s currently exploring the possibility of “epigenetic” changes — or changes around the genome that may occur when one ages, which could lead adults to have a higher risk of adverse effects caused by COVID-19.

However, doctors have warned that a mysterious illness possibly related to COVID-19 is bringing children to hospitals with symptoms ranging from reddened tongues to rashes and enlarged coronary arteries.

Symptoms associated with Kawasaki disease, a rare blood vessel disorder, have appeared to cluster in COVID-19 hot spots, including New York City and the United Kingdom, and now, some Montreal doctors are seeing slightly more cases, too.

Can you develop immunity to the virus?

Whether someone can get the virus again is the “million-dollar question,” Cheng said.

“What we do know is that people can and do develop immunity against the virus, (but) the duration of that immune response is not known.”

There has been discussion in the medical community about the possibility of people who tested positive for COVID-19 developing “protective antibodies” in their blood after the fact.

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A study published in May — whose findings should be interpreted with caution as it has not yet been peer-reviewed or published in a medical journal — followed a group of 160 hospital staff in France who had tested positive for COVID-19 but did not require hospitalization.

The researchers found that nearly all the patients had measurable amounts of antibodies — material produced by the body as it fights off an infection — and that these antibodies were somewhat able to neutralize the virus.

The neutralization appeared to increase over time, though how that translates to immunity isn’t clear.

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Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital, agrees with Cheng.

“We know there is mounting evidence that people who get infected mount an immune response,” Bogoch previously told Global News.

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“There’s very likely to be some degree of immunity to this infection for some period of time. It’s just not clear what the duration of time is.”

It’s also important that note that a positive antibody response “doesn’t necessarily equate to immunity,” Cheng said. “We need to research to try and correlate both of these factors together.”

When is someone with the virus no longer infectious?

With the new coronavirus, the period of infection is likely related to “the person’s ability to shed live virus,” Cheng said.

According to recent research, a person is likely to shed live virus (or be able to give the virus to someone else) for about eight days after symptoms start.

“The cumulative infectivity is probably one to two weeks maximum after symptom onset,” Cheng said.

“Although there are cases of people continually shedding the virus at very low levels (beyond that time), we don’t necessarily believe that they’re capable of transmitting the infection to someone else.”

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Health Canada says while most people experience symptoms five to six days after infection, the incubation period can be up to 14 days.

For those who don’t have symptoms but have tested positive for the virus, it’s important to start counting your isolation period from the date of your first positive test, Dr. Brett Belchetz, a Toronto-based emergency room physician, previously told Global News.

Fourteen days after you test positive or begin your self-isolation period, you can “stop isolating if you no longer have a fever and your symptoms have improved,” Toronto Public Health says.

However, the health agency warns you should continue with COVID-19 prevention measures, like physical distancing and handwashing.

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The Spanish flu had a deadly second wave. Could it happen with COVID-19?

If you are still unwell after those two weeks, you should contact Telehealth or your health-care provider, it adds. Health Canada says two “consecutive negative laboratory test results, at least 24 hours apart,” can be used to determine the end of your infectious period.

Even if you’re less likely to be infectious after 14 days, a person with COVID-19 can still experience symptoms, Belchetz said.

“Research is still evolving in this space, but we’re seeing many patients who have continued to feel symptomatic while repeatedly testing negative for ongoing infection,” Belchetz said.

Why are some areas in Canada affected by the virus more than others?

There is ample evidence to show that COVID-19 has disproportionately affected some areas in Canada more than others.

For starters, more than 80 per cent of the country’s total confirmed cases have been reported in Quebec and Ontario.

And, of the areas with the highest number of cases, there are more Black people living in those neighbourhoods — indicating that there are health inequities impacting those communities due to anti-Black racism, experts previously told Global News.

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Global News analyzed Toronto demographic data alongside new data about which neighbourhoods in Canada’s most populous city have the most coronavirus cases.

The analysis found a strong association between high coronavirus rates and low income, conditions of work, visible minority status and low levels of education. There was an even stronger association between neighbourhoods with a high number of coronavirus cases and those with a higher population of Black people.

The findings for Toronto mirror similar findings for neighbourhoods in Montreal. Data published by the City of Montreal showed that immigrants, refugees and lower-income people live in the hardest-hit regions.

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Coronavirus outbreak: WHO warns threat of resurgence is ‘very real’

And these demographic characteristics are not limited to Canada. New York, one of the most severely impacted cities globally by COVID-19, has higher death rates in poorer neighbourhoods. Black and Hispanic people living in New York City are also twice as likely to die from the virus, compared to white people, according to data from the city.

When asked why some areas are disproportionately affected, Cheng says there isn’t a single explanation.

“It’s probably a combination of many things relating to the at-risk population, recent trial, the timing of public health mitigation strategies,” Cheng said.

Questions about COVID-19? Here are some things you need to know:

Symptoms can include fever, cough and difficulty breathing — very similar to a cold or flu. Some people can develop a more severe illness. People most at risk of this include older adults and people with severe chronic medical conditions like heart, lung or kidney disease. If you develop symptoms, contact public health authorities.

To prevent the virus from spreading, experts recommend frequent handwashing and coughing into your sleeve. They also recommend minimizing contact with others, staying home as much as possible and maintaining a distance of two metres from other people if you go out. In situations where you can’t keep a safe distance from others, public health officials recommend the use of a non-medical face mask or covering to prevent spreading the respiratory droplets that can carry the virus.

In situations where you can’t keep a safe distance from others, public health officials recommend the use of a non-medical face mask or covering to prevent spreading the respiratory droplets that can carry the virus.

For full COVID-19 coverage from Global News, click here.

— With files from Global News’ Laura Hensley, Leslie Young, Olivia Bowden & Patrick Cain

Meghan.Collie@globalnews.ca

© 2020 Global News, a division of Corus Entertainment Inc.

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