Fact check: Can COVID-19 tests be tricked by the influenza virus and other questions answered

Click to play video: 'Flu myths answered by Dr. Roussin' Flu myths answered by Dr. Roussin
Asked why the influenza virus isn't spreading like COVID-19, Manitoba's Chief Provincial Health Officer, Dr. Brent Roussin, offers an explanation – Nov 23, 2020

Misinformation about the flu and COVID-19 have been around since the start of the novel coronavirus pandemic, but now that flu season is upon us, it’s time to fact check some myths.


Myth: If you have influenza and get a COVID-19 test, that test will come back positive for COVID-19.

Fact: The COVID-19 nasal swab test cannot detect influenza, and therefore a false positive is very unlikely.

The type of test that Canada is using, the nasal swab test, is specifically designed to detect SARS-CoV-2, the virus responsible for COVID-19.

The test does this by detecting a very specific genetic sequence in SARS-CoV-2, a genetic sequence that influenza and common cold viruses do not have.

“These genes provide viruses with proteins that allow them to make more copies of themselves, dictate which types of cells they can infect, and can interfere with the circuitry that our cells use to mount immune responses against them,” said Dr. Jason Kindrachuk, assistant professor in the department of medical microbiology at the University of Manitoba.

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“It’s kind of like two bestselling fiction novels — they can both come from the same section of the book store and attract a certain type of reader. However, when you open them up, the words on the pages result in two very different stories.”

In other words, the test that we use looks only for the coronavirus, not influenza, and therefore, influenza cannot produce a false positive.


Myth: If the novel coronavirus is spreading, the flu must also be spreading at equal rates.

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Fact: Immunity, how much harder it is to spread and handwashing are all reasons that flu rates are significantly lower this season so far.

There are several reasons why the flu isn’t spreading, said Kindrachuk.

“This is a result of the additional protective measures that we’re all participating in for COVID-19: distancing, masking, limited time in enclosed areas with low ventilation, hygiene, etc.,” Kindrachuk said.

“Seasonal influenza viruses, while transmitted in a similar way to SARS-CoV-2, appear to be transmitted to a lower number of people per infectious person.”

This means, of course, that the fewer people who get influenza, the fewer people will be infected in the community. Add in protective measures we’ve already been doing since March, and you get a slower spread of the virus, said Kindrachuk.

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“We also have the advantage with influenza viruses of pre-existing immunity through our natural exposure to these viruses during our lifetimes and as well through prior and current vaccinations.

“With COVID-19, we don’t have that buffer of pre-existing immunity in our communities, nor licensed vaccines.”


Myth: The novel coronavirus is no more deadly than the flu.

Fact: The novel coronavirus is three to four times as deadly as influenza in Canada.

According to Canada Public Health, about 3,500 people die yearly from influenza in Canada.

As of Nov. 19, there have been about 11,500 deaths from COVID-19 in Canada since March.

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Myth: SARS-CoV-2 isn’t dangerous for anyone under 60.

FACT: Those under 60 can still have deadly or lifetime health consequences.

“So we’ve known from early on … COVID-19 is very serious and causes significant mortality in people who have pre-existing lung disease and some other conditions like morbid obesity,” said Dr. Alan Katz, director of the Manitoba Centre for Health Policy.

Last week in Manitoba, a woman in her 30s and a child under 10 died from COVID-19. A man in his 20s was also reported dead, but that was corrected later by the province as a clerical error.

Unfortunately, said Katz, those who have had mild illnesses have enhanced the myth that younger people don’t become seriously ill from the virus.

“We know from evidence coming out now that many people who are infected with this illness end up having long-term consequences of it,” said Katz. “And these are quite varied and very concerning and not predictable by the severity of the initial illness.

“We’re seeing people who have mild illness, who don’t need hospitalization at all, also have long-term consequences.

“That’s very concerning, because the whole idea of saying, you know, ‘Let people get a mild form of this illness and then everybody will be fine and immune’ isn’t true,” said Katz.


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