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Fatigue and body aches are symptoms of both the flu and COVID-19, but the flu doesn’t usually cause shortness of breath. Getty Images
  • COVID-19, the flu, a cold, and allergies have different symptoms.
  • The main symptoms of COVID-19 are fever, tiredness, cough, and shortness of breath.
  • Allergies have more chronic symptoms and include sneezing, wheezing, and coughing.
  • The flu has symptoms similar to COVID-19, such as fever and body aches, but it doesn’t usually cause shortness of breath.

If you have a runny nose or itchy eyes, it doesn’t necessarily mean you have COVID-19.

But if you have a cough, fatigue, a fever, shortness of breath, or loss of taste or smell, there’s a much greater chance you have COVID-19.

Then again, it could also be the seasonal flu.

“Not all symptoms are created equally. While it might seem like you have coronavirus, you may simply be experiencing seasonal allergies or influenza,” Lindsey Elmore, PharmD, a board certified pharmacotherapy specialist and host of “The Lindsey Elmore Show,” told Healthline.

It’s worth noting, however, that the 2020-21 flu season was unusually mild, according to the Centers for Disease Control and Prevention (CDC). This is possibly due to preventive steps taken against COVID-19.

“There are many symptoms of cold, flu, and COVID that are similar, and it may be difficult to distinguish,” added Ramzi Yacoub, PharmD, chief pharmacy officer of the prescription savings service SingleCare. “They’re all caused by viruses, but different viruses cause each of these infections.”

“However, one key difference between the three is a symptom of [COVID-19] is shortness of breath,” Yacoub told Healthline. “Shortness of breath is a common sign of COVID-19, which occurs prior to the development of pneumonia.”

“Generally, the flu or a cold does not cause shortness of breath unless it has progressed to pneumonia, in which case you’ll also want to contact your healthcare provider,” Yacoub said.

Dr. Subinoy Das, chief medical officer at Tivic Health, said the common cold rarely causes shortness of breath after fever develops.

“Influenza does mimic COVID-19 very closely, but the shortness of breath is not usually as severe as it is with COVID-19,” Das told Healthline.

With COVID-19, shortness of breath often occurs 5 to 10 days after the first sign of fever, Das noted.

Health officials are expressing concerns about new variants of the coronavirus. So far, several variants are circulating in the United States. The Delta variant currently accounts for more than 90 percent of new infections.

The Delta variant was first detected in the United States in March 2021. Delta — like the others — appears to be more infectious. It causes particularly severe symptoms, although vaccinated people are still highly protected against it.

The Delta variant, which has infected more young people than previous variants, may also cause somewhat different symptoms than other variants.

“If you talk to pediatricians in the field, they tell you that kids are presenting with symptoms associated with the common cold and other upper respiratory infections, such as headache, runny nose, sinus congestion, and sort throat,” Dr. Inci Yildirim, a pediatric infectious disease specialist and a vaccinologist at Yale Medicine in Connecticut, told Healthline.

These symptoms are more often associated with the common cold and weren’t typically associated with earlier presentations of COVID-19.

However, Yildirim cautioned that these reports don’t necessarily mean that the Delta variant causes different symptoms, but rather may reflect COVID-19’s differing impact on younger people.

The most recent mutation of the coronavirus has been designated as the Mu variant. It first emerged in Colombia in early 2021. The Mu variant is currently spreading in the United States, although it only accounts for a small percentage of cases.

Here’s a look at common symptoms of COVID-19, the flu, a cold, and allergies.

A runny nose, facial pain, postnasal drip, and itchy eyes are common symptoms of allergies or the common cold.

But they’re not typical of COVID-19.

“The most common symptoms of COVID-19 are fever, tiredness, and dry cough,” according to the World Health Organization (WHO). “Some patients may have aches and pains, nasal congestion, runny nose, or sore throat.”

“In a report from China of more than 1,000 patients, nasal congestion was seen in only 1 out of every 20 patients,” Dr. Kristine S. Arthur, an internist at MemorialCare Medical Group in Laguna Woods, California, told Healthline.

COVID-19 symptoms usually appear 2 to 14 days after exposure — a window that can be wider than is typical for the flu, which usually presents symptoms within 1 to 4 days of transmission.

The CDC lists 11 primary symptoms of COVID-19:

  • 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

Some people who contract an infection don’t have any symptoms or feel unwell. Nevertheless, these people can still transmit the coronavirus to people around them.

COVID-19, like the flu or common cold, is an acute illness, meaning people feel fine until symptoms start showing up.

Allergies, on the other hand, “are usually chronic, presenting with symptoms off and on for weeks, months, or even years,” Dr. David M. Cutler, family medicine physician at Providence Saint John’s Health Center in Santa Monica, California, told Healthline.

“Allergies should not cause a fever or body aches,” Arthur added. “Generally, [there is] no cough unless you have a lot of nasal drainage.”

Allergies may also cause wheezing, she said, especially in people with asthma.

“Allergy symptoms tend to vary with the environment: worsening with exposure to dust, pollen, or animal dander, whereas cold symptoms tend to persist regardless of time of day, weather, locality, or other environmental factors,” Cutler said.

Also, as with COVID-19, “colds are more likely to have generalized symptoms like fever, headache, and body aches, whereas allergies usually affect only the respiratory tract,” Cutler said.

“Allergy symptoms tend to improve with antihistamine and other allergy-specific medication,” he said. “Colds are more likely to respond to decongestants, acetaminophen, fluids, and rest.”

The CDC issued guidance on the differences in symptoms between COVID-19 and seasonal allergies.

The agency noted that things such as shortness of breath, coughing, fatigue, headache, and sore throat can be symptoms of either COVID-19 or allergies.

Itchy eyes and sneezing are generally only symptoms of allergies.

Fever, muscle aches, a loss of taste or smell, nausea, and diarrhea are associated with COVID-19 and not allergies.

COVID-19 is not the flu.

As one of a class of pathogens known as coronaviruses, COVID-19 is actually more closely related to the common cold than the seasonal flu.

However, despite some overlap, the typical symptoms of COVID-19 are more similar to the flu (fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue) than the common cold (runny or stuffy nose, sore throat, cough, congestion, slight body aches, mild headache, sneezing, low-grade fever, malaise).

The Delta variant, however, may have more cold-like symptoms.

“In terms of differentiating between flu and COVID-19, it can be almost impossible to distinguish,” Dr. Jake Deutsch, co-founder and clinical director of Cure Urgent Care and Specialty Infusion in New York. “That’s why people are recommended to have flu vaccinations so it can at least… minimize the risk of flu in light of everything else.”

“Fevers, body aches, coughing, sneezing could all be equally attributed to them both, so it really means that if there’s a concern for flu, there’s a concern for COVID-19,” Deutsch said.

When and where you get sick might be the best predictor of whether you have a cold, the flu, or COVID-19, Yildirim said.

People living in communities with low vaccination rates and high rates of COVID-19 “are more likely to have COVID-19,” she said, especially outside of cold and flu season.

However, she said, differentiating becomes more difficult during the winter, when all three diseases may be widespread.

If you have a mild case of COVID-19, the flu, or a cold, treatment is geared toward management of symptoms, said Cutler.

“Generally, acetaminophen is recommended for fevers,” he said. “Cough drops and cough syrups can also help keep mucous secretions thinner. If there is associated nasal congestion, antihistamines may be useful.”

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Mild cases of COVID-19 are thought to last approximately 2 weeks, said Cutler.

“Fortunately, the vast majority of cases are mild,” he said.

Almost nobody dies from the common cold. And most seasonal allergies are more annoying than dangerous.

Influenza, however, causes between 12,000 and 61,000 deaths per year in the United States.

COVID-19 can cause more serious illness, especially among unvaccinated people, although treatments have improved in the past year.

Severe symptoms of COVID-19 that require immediate medical attention include:

  • difficulty breathing
  • persistent pain or pressure in the chest
  • confusion or inability to arouse
  • bluish lips or face

Bluish lips or face indicates a shortage of oxygen in the bloodstream.

Among people who develop COVID-19 symptoms, around 15 percent have severe symptoms and need oxygen, according to the WHO.

“People aged 60 years and over, and those with underlying medical problems like high blood pressure, heart and lung problems, diabetes, obesity or cancer, are at higher risk of developing serious illness,” the WHO states.