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We're in the middle of a particularly severe flu season. COVID-19 and other respiratory illnesses, like RSV or the common cold, are also circulating.
Why it matters
More people will be gathering indoors, which means more opportunity for viruses to spread. It's important to know what you're sick with so you can isolate from others who may get severely ill from COVID-19 or the flu.
Many adults may mistake a case of COVID-19 or influenza as 'just as cold' or allergies. Symptoms may overlap, but noting what they are, getting tested and staying home when you're sick can protect the people around you.
'Tis the season for toasty indoor gatherings and the inevitable spread of respiratory viruses. COVID-19 is still with us, as is what's turning out to be the harshest flu season in about a decade.
More people have been hospitalized this flu season compared to the same period every other year going back to the 2010-2011 season, according to information from the US Centers for Disease Control and Prevention. So far, there have been at least 4.4 million flu illnesses, 38,000 hospitalizations and 2,100 flu deaths, the CDC estimates. While hospitalizations and deaths from COVID-19 are, fortunately, still trending down, an average of roughly 300 people in the US per day are still dying from COVID-19.
Because of COVID-19's and the flu's potential to be deadly for some people, you should isolate or stay home while you feel sick, or at least until you get results from a flu or COVID-19 test, which is the only way to know for sure. A rapid, at-home COVID-19 test might be the best first step for a lot of people who happen to have one at home already. Like COVID-19, influenza, which causes the flu, can be particularly severe or deadly for certain folks, including older adults, but also very young children.
To be on the safe side, you should always stay home when you're sick if at all possible -- especially if you have a fever, which is a signal your body is in the active throes of fighting some sort of infection. It also would't hurt to take a rapid COVID-19 test, if you have one, before you gather with people who are more likely to get really sick from the virus.
It's a good time to understand the differences between the three illnesses and what specific symptoms could mean. We also spoke with medical experts to learn the best ways of protecting yourself and your loved ones from diseases this season.
Symptoms of respiratory viruses like COVID-19, the flu and RSV often overlap
Though COVID-19, influenza and colds are all caused by different viruses, symptoms overlap much of the time. And as many people's immune systems become better at fighting COVID-19 through vaccines, booster doses, prior infections and the availability of antivirals like Paxlovid, illnesses may become milder and it may be even easier to brush a COVID-19 infection off as a cold.
Although the loss of smell and taste was the defining unique symptom of COVID-19 earlier in the pandemic, it's less common with the omicron variant, making the fact that you're still able to taste your food an unreliable indicator that you don't have COVID-19. The only way to diagnose your illness for certain is to test for both flu and COVID-19.
In very young children, respiratory syncytial virus can cause symptoms in addition to respiratory problems or flu or cold-like symptoms. Fussiness, losing interest in playing, or seeming more tired than normal may all be symptoms of RSV in babies and toddlers. You can read more about RSV in children here.
What are common symptoms of the flu and COVID-19?
Many respiratory illnesses start with similar symptoms. It may not be easy to immediately figure out whether you're sick with the flu or COVID-19, but here are some symptoms the two share.
Difficulty breathing or shortness of breath
Runny nose or congestion
If you feel sick with any of these symptoms, it's best to isolate yourself right away. You can spread the flu and COVID-19 one day after being infected. Keep in mind that these symptoms may be signs of other viruses, such as the ones that cause the common cold, or RSV. Call your primary care provider for questions and the best next steps.
Remember that COVID-19 isn't only a respiratory illness -- it can also affect a number of other systems in the body, including the heart, brain and nerves. Scientists and medical experts are still defining the range of possible damage from COVID-19.
What are the most common symptoms of COVID-19 right now?
Generally speaking, it's hard to pin down the "most common" symptom of COVID-19, because the virus that causes it changes slightly with each mutation, and people now have varying levels of immunity depending on their vaccination history, previous infections and individual health. But Zoe, a health science company, has been collecting the most common symptoms in people with COVID-19 through the company's COVID Study app. As of Oct. 20, Zoe reports the following top five symptoms in people who've had two vaccines:
While these all are flu-like symptoms, if you experience any of these symptoms in the coming weeks, it may be a strong indicator that you have COVID-19.
Different symptoms between COVID-19 and the flu
The two most notable differences between COVID-19 and the flu are the time it takes for symptoms to show up, and the loss of taste and smell. It generally takes a little longer for COVID-19 symptoms to present after exposure -- two to five days (but up to 14) for COVID-19 versus one to four days for the flu, according to the CDC.
The loss of taste and smell is a specific symptom to COVID-19 that is generally not associated with the flu. However, that symptom was more prevalent with early COVID-19 variants and doesn't appear to be as common with the different versions of omicron.
Another difference between the two viruses is that you could be contagious for longer with COVID-19 than you would be with the flu. Per the CDC, older children and adults with the flu are most contagious through their third or fourth day of symptoms, while people with COVID-19 are contagious, on average, for eight days after their symptoms start.
Symptoms of the flu and COVID-19 can both lead to hospitalization and death. Dr. David Hamer, a Boston University School of Public Health professor and physician at Boston Medical Center, agreed that the symptoms aren't easy to differentiate right away. "Clinically, it's going to be harder for an individual to differentiate. COVID is a little more likely to progress to a severe disease, but certainly, influenza can kill," Hamer said.
How do I know if I have a cold, allergies or something worse?
The symptoms of the common cold are also similar to COVID-19 and the flu, but there are some differences. Fevers aren't as common with a cold, for example, and COVID-19 and the flu are more likely to knock you out of commission, fatigue-wise, for longer than a cold would. You're also less likely to feel "achy" when you have a cold -- another example from the Mayo Clinic.
Like COVID-19, you may notice symptoms such as cough, sore throat and a runny nose. But common colds usually also come with sneezing, watery eyes and post-nasal drip.
Usually, common colds resolve on their own and don't lead to further health complications and often can be treated with over-the-counter medication.
"If there's fever, body aches or chills, that would make me more concerned about other respiratory illnesses -- like the flu or COVID," said Dr. Daniel Solomon, an infectious disease doctor at Brigham and Women's Hospital. Since the COVID-19 vaccine helps prevent severe symptoms, more common signs of a cold can still be COVID, he added.
Because of this, Solomon has guided his patients and family members to pay close attention to their usual allergy symptoms and get a diagnostic test if they notice anything less common.
What is the best way to protect yourself and others from COVID-19 and the flu?
The best protection against both COVID-19 and the flu is vaccination. Medical experts advise that you can safely receive both the flu and COVID-19 shots simultaneously. That includes the new updated boosters. You may also reach out to your doctor as soon as you develop any respiratory symptoms, so you can get the appropriate antiviral treatments or other care, if necessary. This is especially important if you're an older adult or have an underlying medical condition (or have a very young child), as you might be at higher risk of severe disease.
Beyond getting vaccinated, wearing a mask in public, washing your hands before eating or touching your face, avoiding indoor crowds and people who have symptoms are tried and true ways to cut down on your risk of getting a respiratory virus.
What are other common illnesses similar to COVID-19 and the flu?
If you have a cough, sore throat or other respiratory illness symptoms, it may not be COVID-19, the flu or a cold. There are other common illnesses with similar symptoms.
If you tested negative for COVID-19 and the flu, it's best to consult with your primary care provider. Some doctors will conduct a respiratory pathogens panel to determine what virus or bacteria is causing you to feel sick.
CNET contributor Mercey Livingston contributed to this article.
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.