The cold, the flu, and Covid-19 have many overlapping symptoms, including sore throat, coughing, and general fatigue. But each condition also has telltale signs that may help you distinguish between them during the winter months.

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Is it a cold, the flu, or Covid-19?

Even though the 2021-2022 flu season has been mild so far, health care providers have seen an "unprecedented" surge in respiratory viruses since this summer, writes Adrianna Rodriguez for USA Today.

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"You should never underestimate the repertoire and timing of viruses because they're always around," said Len Horovitz, an internist and pulmonary specialist at Lenox Hill Hospital. "I'm seeing just as many colds as I saw this summer, that's not dying."

One challenge with three common viruses now circulating in the United States—the cold, the flu, and Covid-19—is it can often be difficult for people to identify the cause of their illness, especially since many of the symptoms overlap. Specifically, according to CDC, while individuals may react differently to Covid-19, the most common symptoms include:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• New loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea

  In particular, CDC advised individuals to seek immediate emergency medical care if they have any of the following symptoms:

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion
• Inability to wake or stay awake
• Pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone

According to the Palm Beach Post, symptoms for the flu are generally similar, aside from the potential loss of taste or smell. That said, while Covid-19 symptoms usually appear between two and 14 days after exposure, flu symptoms tend to present within one to four days post-exposure. And while Covid-19 symptoms generally last about two weeks, flu symptoms, according to CDC, typically resolve after three to seven days—although symptoms such as weakness and fatigue can linger for up to two weeks. 

Similarly, experts said cold symptoms are also fairly similar, including coughing, sneezing, a stuffy nose, a sore throat, fatigue, and/or a fever. And similar to the flu, these symptoms tend to present between one and three days post-exposure—although, unlike Covid-19, a cold is usually fairly mild, with most people recovering fully within three to 10 days.

Mild symptoms could make it harder to distinguish Covid-19

Another challenge is that even symptom severity may not be a reliable marker, experts said. While Covid-19 and flu symptoms are generally more severe than cold symptoms, Manoj Gandhi, senior medical director for genetic testing solutions at Thermo Fisher Scientific, highlighted the fact that breakthrough Covid-19 infections among vaccinated individuals generally result in milder symptoms—which can make it even harder to identify the illness.  

"When people get vaccinations for the flu [or Covid-19], the whole point of the vaccine is that it makes the disease less severe," Gandhi said. "You get a muted response to the virus ... seeing a mild fever, maybe some weakness here and there."

And although scientists do not yet fully understand the newest Covid-19 variant, the World Health Organization (WHO) has said that there is no evidence to suggest omicron's symptoms are different than any other Covid-19 variants.

"It appears that with the [omicron] cases that are seen, we're not seeing a very severe profile of disease,'' said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases. "In fact, it might be—and I underscore might—be less severe, as shown by the ratio of hospitalizations per number of new cases.''

But just like any other coronavirus variant, WHO said that omicron could still cause severe disease or death—especially among vulnerable populations.

What should you do if you can't tell what's making you sick?

"If you feel sick, don't diagnose yourself," said Deborah German, VP for health affairs and dean at University of Central Florida College of Medicine. "Call your health care provider—don't just show up to the clinic. Your provider can determine if you need to be tested for Covid-19 and what treatments you need."

According to Gandhi, the only definitive way to distinguish a cold from a mild breakthrough infection of Covid-19 is through a PCR test. In fact, patients can be tested for both Covid-19 and influenza using just one swab, Rodriguez writes.

"With one sample you can tell whether it's Covid or influenza A or influenza B," Gandhi said. "If it's neither of them, you know it's probably a cold." 

Still, experts have urged individuals who feel unwell and have any of these symptoms to stay home and follow public health recommendations—such as masking, social distancing, and frequent hand-washing—regardless of their diagnosis. "Stay home and take care of yourself and reduce the exposure," Horovitz said. "People don't want to be around somebody who's sick." (Rodriguez, USA Today, 12/8; Bridges, Palm Beach Post, 12/8)