What Are the Differences Between COVID-19 and the Flu?

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Since the start of the COVID-19 pandemic, various pundits and political officials (including President Trump, after his own hospitalization) have compared the virus to the flu. And for just about as long, public-health officials and epidemiologists have emphasized that COVID-19 is worse. Still, the two have some overlap in symptoms, which can make it hard for someone in the early stages of either to know what they’re sick with. Prior to the start of the flu season, some experts warned of a “twindemic,” when medical resources could be overwhelmed by an influx of patients with the flu, COVID-19, or both. For this reason, getting this year’s flu shot is particularly crucial.

We talked to health experts about the differences (and similarities) between COVID-19 and the flu, plus what you can do to protect yourself from both.

What are the symptoms of COVID-19 vs. the flu?

For people with mild cases of COVID-19, the virus may feel virtually indistinguishable from the flu. While it’s important to remember that COVID-19 can be severe (and it’s not always clear who will get a severe case or why), “the bulk of people who get infected with COVID-19 are either going to have no symptoms at all or their symptoms are really mild,” says Erick Eiting, an emergency-medicine physician at Mount Sinai Beth Israel.

Mild COVID-19 symptoms and flu symptoms have significant overlap. “Most of the time, overlapping signs and symptoms are the onset of fever, soreness of throat, and cough,” says Daisy Dodd, pediatric infectious-disease specialist for Kaiser Permanente in Southern California. “In both, you can have some nasal congestion, some fatigue, body aches, and headache.” Both viruses can also include gastrointestinal symptoms like diarrhea, though these are slightly less common.

COVID-19 may also include more telltale symptoms that distinguish it from the flu, like shortness of breath or lack of taste and/or smell, says Dodd. “If I were to have a patient that calls me and says he had a little bit of a fever and a sore throat and he can’t smell or taste, my No. 1 exclusion diagnosis until proven otherwise is COVID-19,” she says.

At the onset of symptoms that could indicate COVID-19 or the flu, Dodd recommends getting in touch with your doctor, who can evaluate you virtually and arrange an in-person visit if necessary. “Unfortunately, the only way to really know if this is the flu, or if this is COVID, or if it’s something else is to get tested,” adds Eiting.

How long does COVID-19 last vs. the flu?

The duration of COVID-19 symptoms and flu symptoms are both variable, but there are some patterns to each. “With COVID, we usually see about three or four days where you’re feeling the worst, and as you’re getting into your sixth or seventh day, you’re getting better,” says Dodd, adding that severe cases can last much longer.

The flu varies in length, too, but its symptoms tend to resolve more quickly than COVID-19. “Usually the flu is going to be a shorter duration,” says Eiting. “Sometimes it can be as quick as 24 hours, but usually by about three or four days, people are starting to feel better.”

How is COVID-19 treated vs. the flu?

To date, there aren’t many particularly great treatments for either virus. “There’s never really been a great medication to treat the flu,” says Eiting. While doctors may prescribe flu patients with any of a number of antivirals, many have unpleasant side effects, so it’s not always worth it, he says. Most cases of the flu are best treated with rest and fluids, and the best possible treatment is preventing (or reducing severity) with the flu shot.

In most cases of COVID-19, patients will be advised to recover at home, just as they would for the flu, says Eiting. “I don’t think we’re at the point where we have some good recommendations for somebody who doesn’t need to be hospitalized if they’re diagnosed with COVID,” he says. In more severe cases, however, there are a few promising treatments that have proven helpful, including the antiviral remdesivir (though a recent WHO study has called its efficacy into question) and the steroid dexamethasone.

Is COVID-19 deadlier than the flu?

Most medical experts agree that COVID-19 is substantially more deadly than the flu, though it’s hard to pinpoint the exact rate with such a new virus. Scientists haven’t done a particularly good job capturing how deadly the flu is either, says Eiting, because flu testing is insufficient. “The influenza mortality rate is very abstract, whereas the COVID mortality data is much more concrete,” he explains. “We don’t do a good job of testing everybody who we think has influenza each year. There are many people who never go to the doctor because their symptoms get better.” In other words, there are likely more nonlethal flu cases than we realize, which would make the flu’s mortality rate lower.

“People should not be looking at this and saying it’s just the flu,” adds Eiting. “We have seen plenty of young people with no underlying health conditions get very sick and even die of COVID.”

This is not to say, however, that the flu is not dangerous. “They both can be very deadly,” says Dodd. “It’s one of the reasons we recommend immunizations, because being immunized really decreases the chances of getting an infection that costs you your life.”

How do I protect myself against COVID-19 and the flu?

Getting a flu shot has been shown to reduce the likelihood that one will get the flu, as well as one’s risk of becoming seriously ill or dying from it. The flu shot remains the single best tool we have against influenza — and also against getting more seriously ill with COVID-19. “If you get the flu and COVID-19 together, I don’t think that would be a good combination,” says Dodd.

Unfortunately, we do not yet have equivalent protection against COVID-19, and it’s unclear when one (or more) vaccines might become widely available. There is some concern among public-health officials that even when there is a COVID-19 vaccine, too much of the population will be hesitant to get it.

Until an effective, safe vaccine becomes available — and absent strong government leadership — our best protection against COVID-19 remains a collection of imperfect measures: social distancing, thorough handwashing, avoiding touching your face, and wearing a mask around other people.

What Are the Differences Between COVID-19 and the Flu?