COVID and Flu: Similarities and Differences

COVID-19 and the flu have a lot in common. Both are contagious respiratory illnesses that affect your lungs and breathing. But they are caused by two different viruses. Flu viruses have been circulating for about a century. About 1 billion people are thought to get the flu every year. COVID is brand new, appearing for the first time in 2019.

Both COVID and the flu spread through droplets in the air from an infected person coughing, sneezing or talking and can be spread by an infected person for several days before they become sick. Unlike the flu, COVID can also spread through the air. Tiny droplets remain in the air and could cause disease in others, even after the ill person is no longer nearby. This means that COVID is more contagious than the flu.

They share many symptoms in common. Both can cause fever, cough, body aches, fatigue, congestion or runny nose, and sometimes vomiting and diarrhea. COVID has one symptom that the flu does not: a loss of taste or smell. If you have symptoms, your healthcare provider may want you to get tested for both the flu and COVID to see which one it is. While unlikely, it is possible to be sick with both viruses at the same time.

Both COVID and the flu can be mild, severe, or fatal. While healthy people can become seriously ill with both diseases, those who are old, who have underlying medical conditions, and those who are pregnant are at greatest risk. The risk of death among even healthy people who contract COVID-19 is much higher than it is for those who contract the flu.

Both are treated by addressing symptoms, like reducing the fever. Some antiviral medications are available for each. Severe cases of either illness may require hospitalization and support from a ventilator.

Both COVID and the flu can cause lasting damage. COVID may cause damage to the lungs, heart, kidneys, brain, and other organs, especially after severe cases. The flu can cause complications of the heart, brain, and muscle tissues. Multi-organ failure and secondary bacterial infections, like pneumonia, can occur after influenza infection. New information about post-COVID syndrome is being learned all of the time.

You can prevent the spread of both COVID-19 and the flu by washing hands frequently, coughing into the bend of your elbow, staying home when sick, and limiting contact with people who are infected. Distancing from others and wearing a mask in public also helps greatly.

Most importantly, both COVID and the flu are vaccine-preventable diseases. That means that getting a vaccine for each greatly reduces your chances of contracting and spreading the illness. While the vaccines are different, they can be received at the same time. It is highly recommended that people who are age 6 months and older get the flu shot within the month of October, if possible. Everyone age 12 and older should receive the COVID vaccine now. The vaccines for both diseases help ensure the recipients health and the health of their community.

Marie George, MD, FIDSA, is an infectious disease specialist at Southwestern Vermont Medical Center.