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This one symptom means you definitely have coronavirus, not the flu

Published Oct 10th, 2020 2:15PM EDT
Coronavirus Symptoms
Image: Chansom Pantip/Adobe

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  • The coronavirus and the flu have so many symptoms in common, making a clinical diagnosis virtually impossible without testing.
  • There is one “wacky” symptom that stands out, and COVID-19 is the likeliest diagnosis in case it appears, not the flu.
  • The sudden loss of smell and taste is associated with the novel coronavirus. But even so, not all COVID-19 end up losing their sense of smell or taste.

The novel coronavirus is surging again in the US, and a second wave has hist most European countries. What’s different from the March-April wave is that the northern hemisphere is now bracing for the colder season, when the flu usually returns. Scientists have warned for months that a coronavirus-flu convergence, often called a “twindemic,” is a nightmare scenario for health officials and medical systems. Doctors worry they’ll have to deal with flu epidemics on top of the COVID-19 pandemic, and that can be challenging.

These two infectious diseases share many common symptoms that might make a clinical diagnosis impossible without testing. There’s also the possibility of some patients being infected with both pathogens at the same time. But if you’re experiencing many symptoms that are shared between the two illnesses, there is one “wacky” symptom that’s a clear indication of a COVID-19 infection.

The CDC set up a page that explains the differences between the flu and COVID-19. Both illnesses share the same common symptoms, including fever and chills, cough, shortness of breath, fatigue, sore throat, runny or stuffy nose, muscle pain, body aches, headache, vomiting, and diarrhea. The key difference between the two illnesses concerns the sense of smell, the CDC points out. The sudden loss of smell and taste is associated with COVID-19, not the flu.

That’s a point The New York Times makes in a comparison between the two infectious diseases. The loss of smell (anosmia), which triggers the loss of taste (ageusia), is “the one sign that really distinguishes the two infections.”

Some people might experience the symptom because of a stuffy nose, which can happen during a cold or the flu. But that would only be temporary. There’s a high incidence of anosmia right now and various studies have associated it with COVID-19. It’s one of the symptoms included on the CDC’s list of common symptoms as well, and a key sign that will make any doctor suspect a novel coronavirus infection.

Researchers explained that the virus infects cells in the nose that register smell. The inflammation that follows then blocks scents from reaching the nerves that can register smell, so the information never reaches your brain.

You won’t register even strong odors like onions and coffee once you lose your sense of smell from COVID-19, The Times points out. Not all coronavirus patients will exhibit the symptom though, with the paper citing a study saying 13% of people don’t experience it.

A different study said recently that anosmia is actually a good thing, as it’s been linked with a milder form of COVID-19. Yahoo Life notes that 80.4% of subjects who reported the loss of smell then tested positive for COVID-19 in the UK. University College London studied a sample of 590 patients, noting that 77.7% of those who lost their taste also tested positive. Anosmia and ageusia overlap in most cases.

Experiencing flu-like symptoms, but no anosmia or ageusia would not guarantee an infection with the flu. It can still be COVID-19. As we noted before, not all coronavirus patients experience all the possible COVID-19 symptoms. Some people never have any symptoms, or they’re a lot milder.

One other symptom that might be indicative of COVID-19 rather than flu is dyspnea, or difficulty breathing. That’s what some doctors will look for when trying to tell the two conditions apart without tests. Difficulty breathing is a serious symptom that requires immediate medical attention. Keeping an eye on your breathing rate and using a pulse oximeter can help you determine whether oxygen therapy is required. Normal values are 12-16 breaths per minute and 94-100 for blood oxygen readings. The Mayo Clinic states that any blood oxygen saturation level below 90 is considered unhealthy.

There is an unexpected silver lining in all of this. Respecting COVID-19 safety measures can also reduce the flu spread, in which case you would not have to worry about telling them apart. Scientists who have studied this year’s flu pandemic in the southern hemisphere, which already had its 2020 fall and winter seasons, found virtually no flu outbreaks for the region this year. And it’s all because of the overlapping coronavirus pandemic. Social distancing, face masks, and frequent handwashing can prevent the spread of the flu as well, not just the coronavirus.

Chris Smith Senior Writer

Chris Smith has been covering consumer electronics ever since the iPhone revolutionized the industry in 2008. When he’s not writing about the most recent tech news for BGR, he brings his entertainment expertise to Marvel’s Cinematic Universe and other blockbuster franchises.

Outside of work, you’ll catch him streaming almost every new movie and TV show release as soon as it's available.

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