Sign In
Boston Public Health Commission Home

COVID-19 and Flu

​
What is the difference between COVID-19 and Influenza (Flu)?
COVID-19 and Influenza (Flu) are both contagious respiratory illnesses caused by different viruses. COVID-19 is caused by infection with a new coronavirus (called SARS-CoV-2) and flu is caused by infection with influenza viruses. Because the symptoms of flu and COVID-19 are similar, it may be hard to tell the difference between them based on symptoms alone. Testing may be needed to help confirm a diagnosis.

Both COVID-19 and flu symptoms can range from no symptoms (asymptomatic) to severe symptoms.

SymptomsFLUCOVID-19
Fever or feeling feverish/chillsfrequentfrequent
Coughfrequentfrequent
Shortness of breath or difficulty breathingnot oftenfrequent
Fatigue (tiredness)frequentfrequent
Sore throatfrequentnot often
Runny or stuffy nosesometimesnot often
Muscle pain or body achesfrequentfrequent
Headachesometimessometimes
Vomiting and diarrhearare*sometimes
Loss of taste or smellnot describedsometimes

*More common in children than adults

How long do symptoms take to appear after exposure and infection?
For both COVID-19 and flu, several days can pass between a person becoming infected and when that individual begins to experience illness symptoms. If a person has COVID-19, it could take longer to develop symptoms than with the flu. 

  • A person with flu may develop symptoms between 1-4 days after exposure to the virus. 
  • A person with COVID-19 may develop symptoms between 2-14 days after exposure to the virus, but usually is between 4 and 7 days.

How long can someone spread the virus?
For both COVID-19 and flu, it is possible to spread the virus before experiencing any symptoms. If a person has COVID-19, they may be contagious for a longer period of time before symptoms than if they had flu. 
  • Most people with flu are contagious for about 1 day before showing symptoms.
    • Older children and adults with flu appear to be most contagious during the initial 3-4 days of their illness and symptoms, but many remain contagious for about 7 days.
    • Infants and people with weakened immune systems can be contagious for longer periods of time. 
  • People with COVID-19 can 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 is possible to remain contagious for at least 10 days after testing positive for COVID-19.

How does the virus spread?
Both COVID-19 and flu can spread from person-to-person, between people who are in close contact with one another (within about 6 feet). Both are spread mainly by droplets when people with the virus (COVID-19 or flu) cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. It may be possible that a person can get infected by physical human contact (e.g. shaking hands) or by touching a surface or object that has the virus on it and then touching his or her own 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 by people who never developed symptoms (asymptomatic).

Who is at high-risk for severe illness?
Both COVID-19 and flu can result in severe illness and complications. Those who may be at highest risk include:
  • Older adults
  • People with certain underlying medical conditions
  • Pregnant women
The risk of complications for healthy children is higher for flu compared to COVID-19. However, infants and children with underlying medical conditions are at increased risk for complications due to both flu and COVID-19. School-aged children infected with COVID-19 are also at higher risk of Multisystem Inflammatory Syndrome in Children (MIS-C), a rare but severe complication of COVID-19. Additional complications associated with COVID-19 can include: 
  • respiratory failure
  • blood clots in the veins and arteries of the lungs, heart, legs or brain
  • kidney failure and heart abnormalities 
Most people who get flu will recover in a few days to less than two weeks, but complications can include: 
  • pneumonia
  • heart complications.
 
How can Flu and COVID-19 be treated?
People who are hospitalized with flu or at high-risk of flu complications are treated with antiviral drugs as soon as possible. Remdesivir is an antiviral agent that appears to help people with COVID-19 and is currently used to treat COVID-19. Studies are in progress to learn more.  Both illnesses are primarily treated with supportive care.

Is there a vaccine to prevent Flu or COVID-19?
There are multiple influenza vaccines produced annually to protect against the 3 or 4 flu viruses that scientists anticipate might circulate each year. The best way to protect yourself and your loved ones against influenza (flu) is to get a flu vaccine every flu season.  The flu vaccine does NOT prevent COVID-19. Currently, there is no vaccine to prevent COVID-19. Vaccine developers, researchers, and manufacturers are expediting the development of a vaccine to prevent COVID-19.

Is it possible to have the Flu and COVID-19 at the same time?
It is possible to test positive for flu (as well as other respiratory illness) and the virus that causes COVID-19 at the same time.
 

Differences between COVID-19 and Flu

 COVID-19Flu

How many days after exposure will I get sick from the virus?

2-14 days, but usually between 4 and 7 days

1-4 days

How long can someone spread the virus?

 

2 days before symptoms start to 10 days after symptoms started

1 day before symptoms start to 7 days after symptoms started

How does the virus spread?

 

Mainly by respiratory droplets

Mainly by respiratory droplets

Who is at high risk for complications?

  • Older adults

  • People with certain underlying medical conditions

  • Pregnant women

 

  • Older adults

  • People with certain underlying medical conditions

  • Pregnant women

  • Children younger than 5, especially those under the age of 2

 

How can person infected be treated?

 

Primarily treated with supportive care.

Remdesivir is an antiviral agent that is currently used.

Primarily treated with supportive care.

Antiviral drugs should be used as soon as possible.

Is there a vaccine against the virus?

No. Research and development for a vaccine is underway.

Yes. There are multiple vaccines produced annually.

 


OnlineNewsRoomStyles
Boston Public Health Commission
1010 Massachusetts Ave, 6th Floor, Boston, MA 02118.
Phone:(617) 534-5395 Email: info@bphc.org