How to tell if your symptoms are from COVID, a cold or the flu

It’s fall again, bringing Canadians brightly coloured leaves, hot lattes, grey skies – and a whole lot more sniffling and coughing.

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But if you think you’re coming down with something, how do you figure out if your symptoms are from the flu, the common cold, allergies or COVID-19?

The short answer? You can’t.

It’s very difficult to distinguish COVID-19 from other “baseline respiratory tract viruses that people would normally see at this point in the year,” based on symptoms alone, Dr. Zain Chagla told CTVNews.ca in a phone interview.

Three and a half years after COVID-19 spread across the world, the most common symptoms are still ones with a huge overlap with other respiratory illnesses, especially influenza: fever, cough, sore throat and fatigue, among others.

Some of COVID-19’s more unique symptoms, such as the loss of taste or smell, have also become less common as new variants took over – meaning it’s harder than ever to tell the difference.

“People are describing it as their (COVID-19) cases are more cold-like in that sense, which, unfortunately, makes it more difficult to distinguish from typical kind of upper respiratory tract infections that we see at this point in the year,” Chagla, an infectious disease specialist and associate professor at McMaster University, said.

The only real way to be sure if your flu-like symptoms are indeed the flu and not COVID-19 is to test for the virus, experts say. And regardless of which respiratory illness you think you might have, the advice is the same.

“If you're feverish and unwell, you should be staying home until you recover,” Chagla said.

ILLNESSES AND THEIR SYMPTOMS

COVID-19 cases have been seeing an uptick across the country as we head into fall, a reminder that while the virus is no longer circulating with the level of danger that was seen in early 2022 when Omicron emerged, it is still around. Vaccine coverage and the evolution of milder variants over time has helped to lower the risk level for Canadians, but COVID-19 is still capable of causing serious illness or hospitalization and is more infectious than similar respiratory viruses.

If you’re feeling sick right now, it’s far more likely to be COVID-19 than influenza or RSV, according to Dr. Tara Moriarty, infectious diseases researcher and associate professor at the University of Toronto’s Faculty of Dentistry.

Moriarty runs a team which has been tracking COVID-19 levels across Canada as provincial and federal reporting became less frequent. She said that while the number of COVID-19 infections are lower “than it’s been for a lot of the Omicron period,” they’re seeing increases in hospitalizations and deaths.

She told CTVNews.ca in a phone interview that we aren’t seeing much influenza yet, and while there is some RSV, “what we mainly have out there right now is COVID.”

The flu is the colloquial term for a respiratory illness caused by influenza viruses which infect the nose and throat. There are different strains of influenza, such as Influenza A and Influenza B, and the most common symptoms include fever, cough, sore throat, headaches, a runny or stuffy nose and muscle aches.

While COVID-19 has seasonal peaks due to a range of reasons – more people being indoors in the winter means a better opportunity for airborne diseases to spread, for instance – it can be caught at any time of the year. Influenza has a more pronounced seasonal activity. Flu season begins in the fall, with cases usually peaking in winter and winding down in early spring.

We use the term ‘cold’ as a catch-all for mild infections of the nose and throat that cause symptoms that are not too severe and can be dealt with at home. Common symptoms are a runny or stuffy nose, sore throat, cough, sneezing and general muscle aches. Sometimes a mild fever may accompany a cold.

“There's about ten other viruses circulating that are, quote, unquote, ‘the common cold,’” Chagla explained.

Respiratory syncytial virus (RSV), a virus which generally impacts children more frequently but can also be caught by adults, has more lower respiratory tract symptoms than some of the other respiratory viruses set to be circulating this fall. This includes symptoms such as wheezing, Chagla said, which is not something commonly seen in COVID-19 patients or influenza patients.

Although there are some “subtle signs that might not overlap,” in terms of symptoms across these respiratory issues, it’s essentially impossible for the average person to be sure what the source of their illness is, he said, especially if they’re experiencing symptoms common across several types of illness.

Instead of trying to figure out if their cough is just merely part of a cold, experts say Canadians who are feeling under the weather should always try to stay home if possible to mitigate the potential spread of viruses while they recover.

For those who are unable to stay home because their work does not provide sick days, Chagla recommends they wear a mask if they find themselves out in public with symptoms of any type.

“It's getting too difficult to distinguish all of these infections, and without doing a test – and even then, a single test, it’s not perfect – you wouldn't necessarily be able to, and again, outside of maybe nausea, like loss of smell, (the symptoms) really overlap quite a bit.”

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LOSS OF TASTE/SMELL MUCH LESS COMMON IN COVID-19

The one symptom that makes it clear that an illness is probably COVID-19, Chagla said, is still a sudden loss of taste or smell in the absence of any congestion to explain it.

“That one has been much less frequent since coronavirus emerged, but it’s probably the one thing that distinguishes it from the other respiratory viruses,” he said. “All of a sudden losing their sense of smell when there’s not much congestion, anything associated with it that tends to be COVID-19.”

He said that while this symptom is still around, it’s “much, much less apparent than we saw in 2020,” when this symptom was considered one of the predominant symptoms. Now, it’s a “minority of people that have it,” he said, but those that do have this symptom as part of a respiratory illness can be pretty confident that it’s a case of COVID-19.

In terms of other changes over time, as new variants emerged, upper respiratory symptoms became more common while lower respiratory ones became less common, Chagla said.

One study published in the peer-reviewed journal Scientific Reports in March found that lower respiratory features including abnormal lung findings, acute respiratory failure, dyspnea (shortness of breath), hypoxemia (low levels of blood oxygen) and pneumonia decreased with each successive variant. The study, which also found an uptick in upper respiratory symptoms among new variants, covered Delta and Omicron.

Although there’s been changes over time, COVID-19 is still more dangerous than something like influenza, which can be a serious illness in its own right, Moriarty noted.

“In the general population, COVID has a much bigger impact. So even right now, for example, the estimated number of deaths that are occurring, hospitalizations that are occurring for COVID are still nine to 10 times higher than what we would expect for influenza.”

NOT SURE? TEST YOURSELF

Playing symptom detective won’t be able to give you the answers that testing will, but it’s harder to get your hands on a test these days, Chagla said.

He advises that Canadians check with their local public health units, as the availability and location of tests varies by province or territory.

“Rapid tests have been distributed in some provinces to public health units or larger public health organizations, for then distribution into communities,” he said. “Some pharmacies are offering testing, both PCR and rapid testing. And so you know, important to go to your local public health website to see where those resources are.”

Moriarty noted that rapid tests can be negative at first because symptoms may take a few days to develop. The best practice is to test again in a few days if symptoms persist.

“People should test if they're not feeling very well, (and) if it's at all possible, stay home from work or school for a minimum of three days and keep testing for COVID,” she said. “And if you're negative by the third day in a row after your symptoms have developed, it may be something else. But it just takes a while to find out, which is part of the problem.”

Chagla noted that we have more resources for tackling COVID-19 than we did in previous years, such as the antiviral medication, Paxlovid. Available at participating pharmacies across Canada, it’s a pill which can help limit the severity of COVID-19 when taken early on in the course of an infection. Those who are high-risk for developing serious COVID-19 symptoms are eligible for prescriptions.

“We have appropriate influenza vaccines. We have influenza antivirals, we have COVID-19 vaccines, we have COVID-19 antivirals, we now have an RSV vaccine for those over 60 that’s actually now being administered in Canada to high risk individuals,” Chagla said. “I think for folks, especially people who are over the age of 60 or who have medical conditions, it's worth it to just reach out to their providers and say, ‘what can I do to stay up to date going into the season?’”