Do I Have COVID-19 or the Flu?

Last Updated September 2021 | This article was created by familydoctor.org editorial staff and reviewed by Robert "Chuck" Rich, Jr., MD, FAAFP

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If you find yourself feeling under the weather with a fever, body aches, and other symptoms, you may wonder what’s making you feel so bad. Is it seasonal influenza (commonly called the flu)? Or could you have COVID-19? While the two illnesses share many similarities, there are a few differences.

Path to improved health

COVID-19 and the flu are both caused by viruses. But they’re caused by different viruses. COVID-19 is caused by the coronavirus, SARS-CoV-2. Coronaviruses have been around for a long time and coronaviruses can cause you to get the common cold. Flu, on the other hand, is caused by the influenza virus. This is a seasonal virus with two types: Influenza A and Influenza B.

You can catch COVID-19 and the flu in similar ways. When a person talks, sneezes, or coughs, tiny, invisible particles leave their mouth and nose and travel through the air. These particles are where the virus can live. If you breathe in these particles, the virus is then inside your body and can make you sick. Also, if you get the particles on your hands and then touch your mouth, nose, or eyes, you can get sick. This is why it’s so important to wash your hands frequently.

COVID-19 is much more contagious than the flu. That means it passes more quickly and easily from one person to another.

People most at risk

While anyone can get COVID-19 and the flu, some groups of people are at a higher risk of getting sick. For both COVID-19 and flu, adults over 65, people who are pregnant, people with lung disease, heart disease, or diabetes have a greater risk. Children are also at risk for both COVID-19 and flu.

Symptoms

Both COVID-19 and the flu have many of the same symptoms, including:

  • Fever.
  • Cough.
  • Trouble breathing.
  • Extreme tiredness.
  • Sore throat.
  • Stuffy nose.
  • Body aches, including headache.
  • Diarrhea.
  • Vomiting.

If you have COVID-19, you may also lose your sense of smell or taste.

If you have any of these symptoms, contact your doctor right away. They can diagnose which illness you have and also provide advice about what you should do next.

How long are you sick?

It’s possible to spread COVID-19 and the flu to others before you even know you’re sick. If you have COVID-19, you can spread the virus 2 days before you have symptoms. After symptoms begin, you’re likely contagious for 10 days. It’s important to stay away from other people during this time to keep them from getting sick. If you’re around someone who has COVID-19, it can take between 2 and 14 days for you to develop symptoms.

With the flu, you can spread it 1 day before your symptoms begin. Once you have symptoms, you’re contagious for up to 7 days. This time can be longer for kids and seniors. If you’re exposed to someone with the flu, it can take between 1 and 4 days for you to develop symptoms.

People are usually sicker for a longer period of time with COVID-19 than with the flu.

Testing

There are different tests that can confirm if you have COVID-19. Some tests require a cotton swab to be put in your nose. The end of the swab collects a sample from your nasal cavity because this is where the germs live. The swab is then sent to a laboratory for testing. The swab may also be used for a rapid antigen test, however, you may need to confirm a positive or negative result with a laboratory (PCR) test if you still have symptoms or if you need a negative test to return to school or work. A saliva test may be offered and at home (over the counter) tests are also available in some areas. Be sure to check that the test is authorized by the FDA before purchasing.

If your doctor thinks you have the flu, they can perform one of two tests. One test involves putting a swab up your nose. This swab will be sent to the lab for testing. The other test involves collecting a sample from the back of your throat. It will be sent to the lab for testing, too. Rapid tests are also available for flu.

Laboratories have also developed tests that can detect both flu and COVID-19. Talk with your doctor to see if they are available in your area.

Treatment

COVID-19

Three vaccines for COVID-19 have been authorized for emergency use in theare available in the United States from Pfizer-BioNTech and Moderna, and Johnson & Johnson (Janssen). The U.S. Food and Drug Administration (FDA) has authorized the vaccines, and the CDC has recommended the Pfizer-BioNTech’s coronavirus vaccine for people 16 and older and the Moderna and Johnson & Johnson vaccines for people 18 and older.

The Pfizer-BioNTech mRNA vaccine, Comirnaty, was approved by the US Food and Drug Administration (FDA) for individuals 16 years and older. It is still is under emergency use authorization for individuals aged 12-15. The Moderna mRNA vaccine and Janssen (Johnson & Johnson) adenovirus vaccine were authorized by the FDA for individuals 18 years and older. All three vaccines were recommended by the CDC.

In clinical trials, all three vaccines proved to be greater than 94% effective in preventing people from getting seriously ill from COVID-19“across age, gender, race, and ethnicity demographics.” Over 100,000 people were included in the three trials. Additional safety and efficacy data has been collected in over 200 million people who have gotten at least one dose of vaccine. Some rare side effects have been observed, but overall the vaccines are safe and effective at preventing severe disease, hospitalization, and death. These vaccines do not give you COVID-19 and do not cause complications during pregnancy or cause decreases in fertility.

Flu

There is a vaccine you can get to help protect you against the flu. It’s given in the form of a shot in your arm. The American Academy of Family Physicians recommends everyone older than 6 months old get the yearly flu shot, unless their doctor says otherwise. If you get the flu, there are medicines your doctor can prescribe to help you relieve symptoms. Note: The flu shot doesn’t give you the flu.

Recovery time

If you’ve had COVID-19, it will likely take you a long time to recover. It may be weeks before you feel like yourself again and for some people, it may take months (long COVID). Talk with your doctor if you have symptoms that continue as there options for management of these ongoing concerns.

People who have had the flu usually feel much better about 2 weeks after getting sick.

Things to consider

COVID-19 and the flu share many complications. These include pneumonia, respiratory failure, kidney failure, and blood infections. These illnesses can also make existing conditions—including issues with the heart, lungs, and diabetes—worse. In severe cases, both illnesses may lead to death.

If you have COVID-19, you may also develop blood clots in your legs, lungs, heart, or brain. Your chances for these side effects go up if you have heart disease, lung disease, or diabetes. Some children develop multisystem inflammatory syndrome. This is a serious condition, but it isn’t very common.

If you’ve had the flu, you may develop a sinus infection or an ear infection. You may also get pneumonia, which can be serious. Severe side effects are more common in people who are younger than 5 years old or older than 65 years old, pregnant, or who have asthma, diabetes, or heart disease.

Resources

Centers for Disease Control and Prevention: Coronavirus Self-Checker

(click on self-check symptoms on the right side)