COVID-19 vs. Flu: Similarities and Differences
COVID-19 and the flu are caused by different viruses but are both contagious respiratory illnesses with many similar symptoms. The virus that causes COVID-19 is a coronavirus called SARS-CoV-2, whereas the flu is caused by the influenza virus.xxi While we are still learning about COVID-19, experts believe that COVID-19 spreads more easily, shows symptoms after a longer incubation period, remains contagious for longer, and causes more severe symptoms in some than the flu.xxii However, research is still being done, so consult your healthcare provider or your local government to get the latest information on COVID-19.
Many common flu symptoms are also common symptoms of COVID-19. Fever or chills, cough, shortness of breath or difficulty breathing, fatigue, sore throat, runny or stuffy nose, body aches, headache, and vomiting and diarrhea are all symptoms of both COVID-19 and the flu. Cases of both COVID-19 and the flu range from asymptomatic, meaning no symptoms are present, to severe.xxiii One major difference in COVID vs. flu symptoms is that with COVID-19, you may experience a loss of taste or smell.xxiv
Time Between Exposure and Infection
Flu symptoms generally take one to four days to appear after infection. COVID-19 symptoms generally appear five days after infection, but this can range from two days to 14 days after infection.xxv
How It Spreads
Both COVID-19 and the flu are spread when an infected person talks, sneezes, or coughs, releasing droplets into the air that land in the mouths or noses or are inhaled into the lungs of others. Both COVID-19 and the flu can also be spread via surfaces, which includes shaking an infected person’s hand or touching a shared object and then touching one’s own mouth, nose, or eyes.xxvi Someone can spread both COVID-19 and the flu to others even before they start showing symptoms.xxvii Some ways to help mitigate the spread of COVID-19 include wearing a mask and staying at least six feet away from other people who don't live with you.
Someone with COVID-19 is contagious for longer than someone with the flu. Generally, a person with COVID-19 is contagious for 10 days after testing positive or symptoms appear whereas someone with the flu is only contagious for seven days, with days three and four days of the illness being the most contagious period.xxviii
Who Is At Risk?
Older adults, people with underlying medical conditions, and pregnant people are all at higher risk of complications for both COVID-19 and the flu. For healthy children, the risk of complications is higher for the flu than COVID-19.xxix
Possible complications for both COVID-19 and the flu include the following:
- Respiratory failure
- Multiple-organ failure
- Heart attack or stroke
- Acute respiratory distress syndrome
- Worsening of chronic conditions of the heart, lungs, nervous system, or diabetes
- Heart, brain, or muscle tissue inflammation
- Secondary bacterial infectionxxx
If you’re in a high-risk group for the flu or COVID-19, or if you experience severe symptoms for either illness, seek medical attention right away.
We hope this article has helped you better understand the similarities and differences between COVID vs. flu vs. cold symptoms. However, this guide is not a replacement for medical diagnosis—if you are feeling sick, make sure to talk to your doctor or trusted healthcare provider. For information on cold vs. flu, visit the Theraflu guide to cold and flu symptoms.
i. Symptoms of Coronavirus. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html. Accessed 11/03/20. Referenced text indicated in red on sourcing doc.
ii. Flu Symptoms & Complications. Centers for Disease Control and Prevention. https://www.cdc.gov/flu/symptoms/symptoms.htm. Accessed 11/03/20. Referenced text indicated in red on sourcing doc.
iii. Common Cold. Centers for Disease Control and Prevention. https://www.cdc.gov/antibiotic-use/community/for-patients/common-illnesses/colds.html. Accessed 11/03/20. Referenced text indicated in red on sourcing doc.
iv. Coronavirus. World Health Organization. https://www.who.int/health-topics/coronavirus. Accessed 11/03/20. Referenced text indicated in red on sourcing doc.
ix. Key Facts About Influenza (Flu). Centers for Disease Control and Prevention. https://www.cdc.gov/flu/about/keyfacts.htm. Accessed 11/04/20. Referenced text indicated in red on sourcing doc.
xv. Common cold. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/common-cold/symptoms-causes/syc-20351605. Accessed 11/04/20. Referenced text indicated in red on sourcing doc.
xxi. Similarities and Differences between Flu and COVID-19. Centers for Disease Control and Protection. https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm. Accessed 11/04/20. Referenced text indicated in red on sourcing doc.