Both COVID-19 and influenza are contagious respiratory illnesses, but they are caused by different viruses. Many symptoms of the two are similar, which can cause confusion about which one you may be suffering from.
The Centers for Disease Control and Prevention says COVID-19 seems to spread more easily and can cause more serious illnesses in some people. Ultimately, testing may need to be done to determine which, if any, virus you have.
Here’s how the two illnesses compare.
Symptoms shared by COVID-19 and influenza
The severity of both COVID-19 and flu can range from no symptoms (asymptomatic) to severe symptoms.
Shared symptoms include:
- Fever or chills.
- Shortness of breath or difficulty breathing.
- Sore throat.
- Congestion or running nose.
- Muscle or body aches.
- Vomiting or diarrhea (more common in children).
Differences in COVID-19 and influenza symptoms
So far, research indicates there may only be one significant difference in symptoms between COVID-19 and the flu:
- The change in or loss of taste and smell.
Because of this, you may need to see a doctor for testing to determine which virus, if any, you have.
There are a few other notable similarities and differences between influenza and COVID-19.
- Similarities: The CDC says both viruses can spread for at least one day before a person shows symptoms.
- Differences: A person with the flu may be contagious for up to seven days, compared with COVID-19, which could spread for up to 10 days after someone shows symptoms or tests positive.
How the viruses spread:
- Similarities: Both COVID-19 and the flu can spread from person-to-person when they’re within about 6 feet of each other. Both are spread mainly by respiratory droplets exerted when someone coughs, sneezes or talks. Both may be spread by people before they begin showing symptoms, by people with very mild symptoms, and by people who never develop symptoms (asymptomatic).
- Differences: COVID-19 is more contagious among certain groups of people than the flu. It can also spread quickly and easily, leading to more “superspreading” events – situations in which one person infects a lot of other people who then spread it to more people.
People at high risk:
- Similarities: Both viruses can cause severe illness for older adults, people with certain underlying medical conditions and pregnant women.
- Differences: The risk for complications for healthy children is higher with the flu. However, infants and children with underlying medical conditions are at increased risk for both flu and COVID-19. Additionally, school-aged children with COVID-19 are at higher risk for Multisystem Inflammatory Syndrome in Children (MIS-C), a rare but severe complication of COVID-19.
- Similarities: Both COVID-19 and flu can cause these complications:
- Respiratory failure
- Acute respiratory distress syndrome (fluid in the lungs)
- Cardiac injury (heart attacks and stroke)
- Multiple-organ failure (respiratory failure, kidney failure, shock)
- Worsening of chronic conditions (involving the lungs, heart, or nervous system or diabetes)
- Inflammation of the heart, brain or muscle tissues
- Secondary bacterial infections (infections in people who have already had the flu or COVID-19)
- Differences: COVID-19 can also cause blood clots in the lungs, heart, legs or brain, and cause Multisystem Inflammatory Syndrome in Children (MIS-C).
- Similarities: People can protect themselves and others against both illnesses by:
- Avoiding close contact with people who are sick.
- Self-quarantining when they’re symptomatic.
- Wearing a mask.
- Washing hands often.
- Cleaning and disinfecting surfaces and objects.
- Getting vaccinated.