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K-State Today

December 3, 2020

COVID-19 and flu: What's the difference?

Submitted by Lafene Health Center

COVID-19 and influenza, or flu, are both contagious respiratory illnesses, but each is caused by a different virus. While there are similarities between the two illnesses, there are also some key differences. COVID-19 appears to spread more easily than the flu and causes more serious illness. Some of the symptoms of flu and COVID-19 are similar and it can be hard to distinguish based on symptoms alone. Testing may be necessary to confirm a diagnosis.

Read the following information from the Centers for Disease Control and Prevention on the similarities and differences between flu and COVID-19.

Signs and symptoms


COVID-19 and flu both have varying degrees of signs and symptoms. Common symptoms that both illnesses share:

  • Fever/feeling feverish or chills.
  • Cough.
  • Shortness of breath or difficulty breathing.
  • Fatigue/tiredness.
  • Sore throat.
  • Runny or stuffy nose.
  • Muscle pain or body aches.
  • Headache.
  • Some people may experience vomiting and diarrhea, though this is more common in children than adults.


  • Flu can cause mild to severe illness, including the common signs and symptoms listed above.
  • COVID-19 appears to cause more serious illnesses in some people and sometimes even hospitalization. Another common symptom of COVID-19 may include change in or loss of taste or smell.

Exposure to infection timeline


  • For both COVID-19 and flu, one or more days can pass between a person becoming infected and when he or she starts to experience illness symptoms.


  • If a person has COVID-19, it can take longer to develop symptoms than the flu. A person usually develops symptoms of the flu anywhere from one to four days after infection. Typically, a person develops COVID-19 symptoms five days after being infected, but symptoms can appear as early as two days after infection or as late as 14 days after infection, and the time range can vary.

Contagious period


  • For both COVID-19 and flu, it's possible to spread the virus for at least one day before experiencing any symptoms.


  • If a person has COVID-19, he or she may be contagious for a longer time than the flu.
  • Most people with flu are contagious for about one day before they show symptoms. Older children and adults with flu appear to be most contagious during the initial three to four days of their illness but many remain contagious for about seven days.
  • How long someone can spread the virus that causes COVID-19 is still under investigation. It's possible for people to spread the virus for about two days before experiencing signs or symptoms and to remain contagious for at least 10 days after signs or symptoms first appeared. If someone is asymptomatic or symptoms go away, it's possible to remain contagious for at least 10 days after testing positive for COVID-19.

Spreading the viruses


  • Both the new coronavirus and influenza viruses can spread from person to person and between people who are in close contact with one another, or within about 6 feet. Both viruses are spread mainly by droplets made when people with the illness cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or can possibly be inhaled into the lungs.
  • It may be possible that a person can get infected by physical human contact, such as shaking hands or by touching a surface or object that has virus on it and then touching his or her mouth, nose or possibly eyes.
  • Both flu virus and the virus that causes COVID-19 may be spread to others by people before they begin showing symptoms, by people with very mild symptoms or even by people who are asymptomatic and never develop symptoms.


  • Coronavirus is more contagious among certain populations and age groups than influenza. Also, COVID-19 has been observed to have more superspreading events than flu. This means the virus that causes COVID-19 can quickly and easily spread to a lot of people and result in continuous spreading among people as time progresses.



  • Vaccines for COVID-19 and flu must be approved or authorized for emergency use by the Food and Drug Administration, or FDA.


  • There are multiple FDA-licensed flu vaccines produced annually to protect against the three or four flu viruses that scientists anticipate will circulate each year.
  • As of Nov. 30, two COVID-19 vaccines are going through approval processes but are not yet available for the general public.

Lafene Health Center offers flu vaccines and COVID-19 testing. Schedule an appointment through the myLafene+ patient portal or by calling 785-532-6544.

Find more CDC tips to reduce risk and stop the spread of COVID-19 and learn more about health and wellness at K-State.