COVID-19 and flu  are both contagious respiratory illnesses but they are 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 virus. It may be  hard to tell the difference between a flu and COVID-19 because the symptoms are similar so testing may be needed to confirm a diagnosis.

Signs and symptoms

Similarities

• Fever or chills
• Fatigue
• Sore throat
• Runny or stuffy nose
• Difficulty breathing or shortness of breath
• Headache
• Muscle pain and body-aches
• Cough
• Some people may experience vomiting and diarrhea  though this is more common in children than adults.

Differences

COVID-19

• Symptoms of COVID-19 that may be different from flu include change in or loss of taste and smell.

Flu

• Flu can cause mild to severe illness including the common symptoms listed above .

How long do symptoms appear when you get exposed or infected

COVID-19

Similarities

• For both viruses, 1 or more days  can pass between a person becoming infected  and when he or she  starts  to the experience symptoms.

Differences

It could take longer for a person with COVID-19 to show symptoms that a person with flu.

COVID-19

With COVID-19,  a person develops symptoms 5 days after being infected  but symptoms can appears early as 2 days after infection or as late as 14 days after infection, and the time range can vary.

Flu

A person typically develops symptoms anywhere from 1 to 4 days after infection.

People at high risk of for severe infection

Similarities 

Both COVID-19 and flu can result in severe illness  and complications. Those at high risk include the following :

• Older adults
• People with certain underlying medical condition
• Pregnant women

Differences

The risk for complications for healthy children is higher  for flu and COVID-19. However  infants and children with underlying medical conditions are at increased  risk for both flu and COVID-19.

Flu

Young children are at higher risk fo severe illness  from flu.

COVID-19

School aged children infected with COVID-19 are at higher risk of Multisystem Inflammmatory Syndrome in Children MIS-C , a rare but  severe complication of COVID-19

Complications

Similarities

Both COVID-19 and flu can result in complications including the following :

• Respiratory failure
• Pneumonia
• Sepsis
• Cardiac Injury  such as heart attaches and stroke
• Acute respiratory distress syndrome that is fluid in the lungs
• Multiple organ failure respiratory failure, kidney failure, shock
• Secondary bacterial infections that is infection that occur in people  who have already been infected with COVID-19 or flu.
• Inflammation of the heart, brain or muscle tissue
• Worsening of chronic medical  condition involving the lungs, heart, nervous system and diabetes .

Differences

COVID-19

Additional complications of COVID-19 include

• Blood clots in the veins and arteries of the lungs, heart , legs and brain,
• Multisystem Inflammatory Syndrome in Children

Flu

Most people with flu recover from a few days to less than 2 weeks but some develop complications.

Vaccine

Similarities

Vaccines for COVID-19 and flu must be approved or authorized for emergency use (EUA) by the FDA.

Differences

COVID-19

• There is currently no vaccine for COVID-19. Vaccine developers and other researchers and manufacturers are expediting the development of a vaccine to prevent COVID-19.

Flu

• There are multiple FDA-licensed influenza vaccineproduced annually to protect against the 3 or 4 flu viruses that scientists anticipate will circulate each year.