There are many similarities between influenza (flu) and COVID-19. Both are caused by viruses, but they are not caused by the same virus. The CDC has a detailed report.
What’s the same and what’s different between COVID-19 and flu?
The CDC says because some of the symptoms of flu and COVID-19 are similar, it may be hard to tell the difference between them based on symptoms alone, and testing may be needed to help confirm a diagnosis. Flu and COVID-19 share many characteristics, but there are some key differences between the two.
Similarities:
Both COVID-19 and flu can have varying degrees of signs and symptoms, ranging from no symptoms (asymptomatic) to severe symptoms. Common symptoms that COVID-19 and flu share include:
- Fever or feeling feverish/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 have vomiting and diarrhea, though this is more common in children than adults
Differences:
Flu
Flu viruses can cause mild to severe illness, including common signs and symptoms listed above.
COVID-19
Other signs and symptoms of COVID-19, different from flu, may include change in or loss of taste or smell.
How long from exposure to the virus to symptoms, generally?
For both COVID-19 and flu, 1 or more days can pass between a person becoming infected and when he or she starts to experience illness symptoms.
Differences:
If a person has COVID-19, it could take them longer to develop symptoms than if they had flu.
Flu
Typically, a person develops symptoms anywhere from 1 to 4 days after infection.
COVID-19
Typically, a person develops symptoms 5 days after being infected, but symptoms can appear as early as 2 days after infection or as late as 14 days after infection, and the time range can vary.
How long is one contagious, when can one spread the virus?
For both COVID-19 and flu, it’s possible to spread the virus for at least 1 day before experiencing any symptoms.
Differences:
If a person has COVID-19, they may be contagious for a longer period of time than if they had flu.
Flu
Most people with flu are contagious for about 1 day before they show symptoms.
Older children and adults with flu appear to be most contagious during the initial 3-4 days of their illness but many remain contagious for about 7 days.
Infants and people with weakened immune systems can be contagious for even longer.
COVID-19
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 2 days before experiencing signs or symptoms and remain contagious for at least 10 days after signs or symptoms first appeared. If someone is asymptomatic or their symptoms go away, it’s possible to remain contagious for at least 10 days after testing positive for COVID-19.
For more information, including information about those with high risk, complications of both flu and COVID-19, click here for the detailed CDC report.