Updated March 1, 2021
The novel coronavirus — severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) —draws comparisons to influenza, the seasonal flu.
Reports of SARS-CoV-2 and COVID-19, the disease it causes, began in China in late December 2019 — the middle of flu season.
COVID-19 and the flu cause similar respiratory symptoms, but the two have many differences.
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Similarities Between COVID-19 and the Flu
Both the flu and COVID-19 are respiratory diseases, but they come from different viruses. Novel coronavirus SARS-CoV-2 causes COVID-19, while influenza viruses cause the flu. But they do share several similarities.
How the flu and COVID-19 spread
Both the flu and COVID-19 can spread from person to person with close contact. If an infected person coughs, sneezes, breathes, or talks, they release respiratory droplets that can land in another person’s nose, eyes, or mouth.
The flu also can spread if uninfected people touch a surface that contains the virus and then touch their nose, mouth, or eyes. COVID-19 can spread in a similar way, although it is more commonly spread through respiratory droplets.
You do not need to be symptomatic to spread COVID-19 or the flu. Both can be spread by people who are not yet showing symptoms.
Groups at risk
Older adults, people with underlying health conditions (such as lung disease, heart disease, and diabetes), and pregnant women are at higher risk for severe illness from both COVID-19 and the flu. Children under 1 year old and children with certain medical conditions are also at higher risk for severe illness from both COVID-19 and the flu.
Children without underlying health conditions are more at risk of severe illness from the flu than from COVID-19. COVID-19 symptoms in children are generally less severe, but they can get seriously ill. Scientists are investigating a serious inflammatory condition associated with COVID-19, known as Multi-system Inflammatory Syndrome in Children (MIS-C).
Flu symptoms vs. COVID-19 symptoms
Both the flu and COVID-19 cause similar symptoms, ranging from no symptoms at all to severe. In the most severe cases, both can cause serious illness or death.
The most common symptoms shared by the flu and COVID-19 include:
- Fever or feeling feverish/chills
- Shortness of breath or difficulty breathing
- Fatigue (tiredness)
- Sore throat
- Runny or stuffy nose
- Muscle pain or body aches
- Vomiting/diarrhea (more common in children)
One symptom associated with COVID-19 but not with the flu is the loss of taste or smell.
Both the flu and COVID-19 can cause serious health complications like pneumonia, respiratory failure, organ failure, heart damage, and more.
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Differences Between COVID-19 and the Flu
The flu and COVID-19 do share similarities. However, they are different diseases and it is important to know the distinctions.
Tens of millions of people have been infected worldwide with the coronavirus since late 2019, according to the World Health Organization.
The flu is more common on an annual basis. The Centers for Disease Control and Prevention (CDC) estimates the flu affects between 9 million and 45 million people each year in the United States alone.
However, COVID-19 appears to be deadlier. Millions of people have died worldwide from COVID-19 since late 2019, according to the WHO. It also reports between 290,000 and 650,000 people worldwide die each year because of severe flu-related respiratory problems.
COVID-19’s death rate is changing, but it remains higher than the flu, which has a yearly fatality rate of around 0.1%.
COVID-19 also causes more serious illnesses in some people, the CDC says.
Other key differences between the two diseases include:
Contagiousness of the flu and COVID-19
It’s possible to spread both the flu and COVID-19 before showing any symptoms (that means you’re asymptomatic).
The length of time it takes to develop symptoms — if you ever do — differs. With the flu, most people develop symptoms within 1 to 4 days after infection. For COVID-19, symptoms can show up anywhere between two and 14 days, with five days being most common.
Also, how long you can spread the diseases differs:
- With the flu, older children and adults are usually most contagious for the first three or four days of their illness. Many can be contagious for up to a week, and infants and young children can be contagious even longer.
- Scientists are still studying how long someone can spread COVID-19. It’s possible to be contagious at least two days before any symptoms appear. You may remain contagious for at least 10 days after symptoms appear, but it may be even longer. Even if you were asymptomatic or your symptoms went away, it’s possible to be contagious for 10 days or longer after testing positive for COVID-19.
Testing for the flu and COVID-19
Because of the similarities of symptoms between COVID-19 and the flu, testing is likely necessary for a definitive diagnosis.
Several different tests can diagnose the flu, and those tests are widely available.
Laboratory tests are the most common way COVID-19 is diagnosed. The current tests for a COVID-19 infection are known as viral tests or diagnostic tests. According to the Food and Drug Administration, they include molecular tests, which look for the virus’ genetic markers, and antigen tests, which can detect proteins on the virus’ surface. At UPMC, we use molecular tests. Specimens can be collected from multiple sites in your nasal cavity or mouth.
If you are experiencing symptoms consistent with COVID-19, or if you have been in close contact with someone with suspected or confirmed COVID-19, call your doctor about testing.
Treatment for the flu and COVID-19
If you have the flu, prescription antiviral medicines can help treat your illness, if taken early. They can help ease your symptoms, shorten your illness, and lessen your risk for complications.
The Food and Drug Administration has approved remdesivir as a drug to treat severe COVID-19. Other treatments for severe illness have received Emergency Use Authorization (EUA). For more minor illnesses, doctors may recommend over-the-counter medications like acetaminophen or ibuprofen to treat symptoms.
Can I Prevent Coronavirus or the Flu?
The CDC recommends that everyone older than 6 months get an annual flu shot, which can help prevent you from getting infected with the flu.
Three COVID-19 vaccines have received Emergency Use Authorization from the FDA. Distribution has begun in the United States.
Other methods to help prevent the spread of COVID-19 include:
- Facemasks: Follow the CDC’s recommendations for wearing facemasks. The CDC recommends wearing a facemask when out in public to prevent spread of the coronavirus. Pennsylvania currently requires the use of facemasks in all indoor settings when not around people from your household, and in outdoor settings when you can’t keep a distance of 6 feet from people not from your household. Children under age 2 should not wear facemasks. You should not purchase masks or respirators that are meant for health care workers. Learn more about facemask use, including how to craft your own at home.
- Social distancing: When out in public, maintain at least 6 feet of distance from people who are not members of your household.
There are also prevention methods you can use for both the coronavirus and the flu. These steps can help protect you from getting infected by the flu or COVID-19 and help prevent their spread:
- Avoid contact with people who are infected
- Stay home if you’re sick
- Cover your mouth and nose when you sneeze or cough
- Wash your hands with soap and water or an alcohol-based hand sanitizer. Wash for at least 20 seconds — especially after coughing and sneezing, using the bathroom, and before eating
- Avoid touching your nose, eyes, or mouth
- Disinfect commonly touched surfaces, such as tables and counters, at work, home, and school
- Wash your hands after touching commonly used surfaces
For more information on the coronavirus, visit UPMC.com/COVID19.
About Infectious Diseases
If you have a disease caused by bacteria, fungi, parasite, or virus, the UPMC Center for Care of Infectious Diseases can help. We have specialty units for prevention and treatment of HIV-AIDs, postsurgical and transplant infections, and illnesses caused by international travel. Our faculty research infectious diseases and participate in clinical trials to learn more and develop better treatment and prevention methods.