Is it a cold, the flu or COVID? How to tell the difference

During the COVID-19 pandemic, a cough, sneeze or sore throat can inspire panic. Learn how to tell viral infections apart.

Similar symptoms of COVID and influenza make it hard to know for sure without testing.
Sarah Tew/CNET
For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

A nasty flu season and the rise of seasonal colds have combined with the new omicron variant of COVID-19 to create an infernal mix of viral infections this winter. If your throat starts itching or you feel fatigued, how are you supposed to know if it's COVID-19, flu or a cold?

The COVID-19 virus has infected more than 315 million people worldwide and killed at least 5.5 million. The main symptoms of COVID-19 are a cough, usually dry, as well as fever and excessive body fatigue. If you are experiencing any of those symptoms, get tested for COVID as soon as possible. The deadly serious nature of COVID-19 makes it important to identify and isolate the infected, particularly from people who are immunocompromised, seniors or in other high-risk categories.

Whether or not you're currently feeling sick, 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.

Plus, here's what you need to know about getting the flu shot, mixing and matching COVID-19 booster shots, the latest on COVID-19 vaccines for kids and what's happening with the Pfizer COVID pill

What are the most common symptoms of COVID-19, the flu, colds and allergies?

Though COVID-19, influenza and colds are all caused by different viruses, many of their symptoms overlap. It is also possible to be infected with more than one virus at a time. Recent cases of "flurona" -- a combination of COVID-19 and the flu -- have made news across the US. 

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 currently dominant omicron variant. The only way to diagnose your illness for certain is to test for both flu and COVID-19.

The table below shows the specific symptoms for COVID-19, flu, colds and allergies.

Different symptoms of COVID, Flu, Colds and Allergies

COVID-19 Flu Common cold Allergies
Cough Common Common Sometimes No
Sneeze  Rare Sometimes Common Common
Fever Common Common No No
Fatigue Common Common No No
Body aches Common Common Rare No
Runny nose or congestion Sometimes Sometimes Common Common
Sore throat Common Common Common No
Headache  Sometimes Common No Sometimes
Loss of taste or smell  Common No Rare No
Difficulty breathing Common Sometimes No No
Vomiting/Diarrhea Sometimes Sometimes No No

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.

  • Cough 
  • Fever
  • Difficulty breathing or shortness of breath 
  • Sore throat
  • Runny nose or congestion
  • Headache 
  • Body aches 

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 rhinoviruses that mostly cause the common cold, or RSV. Call your primary care provider for questions and the best next steps. Get tested if possible.

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 differences between the flu and COVID-19?

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 longer for COVID-19 symptoms to present after exposure -- two to 14 days for COVID-19 versus one to four days for the flu.

The loss of taste and smell is a symptom specific to COVID-19 that is generally not associated at all with the flu. However, that symptom was more prevalent in early COVID-19 variants and not as common with omicron.

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. 

Can I get COVID and the flu at the same time?

You can certainly be infected with the flu and COVID-19 at the same time. Dr. Hamer noted that someone with COVID may struggle greatly with additional flu symptoms. 

"It has been reported, but it turns out that we don't have a lot of experience with coinfection because last year when we had a really big surge of COVID, it was the lightest flu season on record," said Dr. Daniel Solomon, an infectious disease doctor at Brigham and Women's Hospital.

Unfortunately, this year's flu season looks much worse. A less effective flu vaccine and reduced COVID restrictions have led to an early spike in cases that is already far higher this season compared to 2020-21.

"If someone comes in with a fever and a headache, it's going to be hard for us to know if it's flu or if it's COVID. That's why a lot of health care systems are moving towards testing for both flu and COVID at the same time," said Dr. Ala Dababneh, an infectious disease doctor with Mayo Clinic. Doctors may also test for RSV. 

Someone infected with both the flu and COVID-19 may have a more severe illness and complications that could lead to hospitalization. Supportive care can treat COVID-19 symptoms, and antiviral drugs can be used to treat the flu. Remdesevir, the approved antiviral treatment for COVID-19, is administered via IV and requires five days of treatment in a hospital. The FDA recently authorized Pfizer's therapeutic COVID pill , but limited supplies will likely restrict the treatment to the elderly and immunocompromised. 

COVID-19 home testing kit

An at-home COVID-19 test can help determine your illness.

Stephen Shankland/CNET

What are 'long COVID' and 'long flu'? 

Some people experience longer-term COVID-19 and flu symptoms, commonly known as "long COVID" or "long flu." Long COVID can include shortness of breath, headaches, chest pains, fatigue and other COVID-19 symptoms that linger for weeks or months. Long flu symptoms can consist of a prolonged cough, sore throat, body aches and other symptoms lasting longer than five to seven days

A PLOS Medicine survey found that long COVID is more likely than long flu. Those that had a severe case of COVID-19 or were hospitalized due to the virus were more likely to experience symptoms longer, but most resolved within six months. 

How do I know if I have a cold or COVID-19?

The symptoms of the common cold are also similar to COVID-19 and the flu. 

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. However, it may be harder for doctors to diagnose right away if you have other symptoms on top of signs of a common cold. 

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.

Here's a list of COVID-19 symptoms that are different from common colds:

  • Loss of taste or smell 
  • Difficulty breathing or shortness of breath 
  • Fever 
  • Body aches 
  • Chest pains 
  • Difficulty breathing
  • Nausea or diarrhea

"If there's fever, body aches or chills, that would make me more concerned about other respiratory illnesses -- like the flu or COVID," Solomon said. 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. While breakthrough cases of COVID -- infections in fully vaccinated people -- are rising due to the more contagious omicron variant, those cases are far less likely to cause hospitalization and death.

Recent evidence continues to confirm the importance of booster shots for COVID-19 . Protection from COVID vaccines decreases over time, particularly against omicron. The CDC now recommends the two mRA vaccines from Pfizer and Moderna over the vaccine from Johnson & Johnson. That recommendation also applies to booster shots, which are recommended five months after an initial vaccination with Moderna or Pfizer and two months after an initial vaccination with Johnson & Johnson.

After getting vaccinated for COVID-19, the CDC also advises wearing a mask in indoor public spaces, staying at least 6 feet away from others, avoiding crowds and testing regularly.

At-home COVID tests have become valuable tools for diagnosing early infections, though they've also become difficult to find. The Biden administration is currently finalizing a plan to make at-home tests free and provide 500 million of them to Americans.

If you're ever unsure about your symptoms or illness, it's best to get tested. Remember to follow other well-known hygiene tips, like washing your hands often, disinfecting frequently touched surfaces and staying home if you're not feeling well. 

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.

  • Sinus infections 
  • Strep throat 
  • Bronchiolitis 
  • Asthma 

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. 

Here are the flu shot side effects to know about this year and the latest on the omicron variant of COVID-19. And here's the latest on the COVID-19 vaccine mandates for employers with over 100 employees, federal employees and other groups.

CNET contributor Mercy 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.