Influenza (the flu) and COVID-19, the illness caused by the pandemic coronavirus, are both contagious respiratory illnesses, meaning they affect your lungs and breathing, and can be spread to others. Although the symptoms of COVID-19 and the flu can look similar, the two illnesses are caused by different viruses.
Similarities: COVID-19 and the Flu
Symptoms
- Both illnesses can cause fever, cough, body aches, and sometimes vomiting and diarrhea (especially in children). Learn more about COVID-19 symptoms.
- Both can result in pneumonia.
- Both flu and COVID-19 can be asymptomatic, mild, severe or even fatal.
How It Spreads
- Both the flu and COVID-19 spread in similar ways. Droplets or smaller virus particles from a sick person can transmit the virus to other people nearby. The smallest particles may linger in the air, and another person can inhale them and become infected.
- Or, people can touch a surface with viruses on it, and then transfer the germs to themselves by touching their face.
- People infected with the coronavirus or the flu may not realize they are sick for several days, and during that time can unknowingly spread the disease to others before they even feel sick.
Prevention
In most cases, serious disease and death due to COVID-19 or the flu can be prevented by vaccines. In addition, mask-wearing, frequent and thorough hand washing, coughing into the crook of your elbow, staying home when sick and limiting contact with people who are infected are effective safety precautions. Physical distancing limits the spread of COVID-19 and flu in communities.
Differences: COVID-19 and the Flu
Cause
COVID-19: Caused by the 2019 coronavirus, also known as SARS-CoV-2. There are different SARS-CoV-2 that have some differences in how severe or transmissible they are.
Flu: Caused by the influenza virus. There are two main types of influenza virus called influenza A and influenza B. Different strains of influenza A and influenza B emerge and circulate each year.
Symptoms
COVID-19: Many people infected with the coronavirus do not feel sick or have only mild symptoms, but they can still transmit the coronavirus to other people. Review the full list of symptoms.
COVID-19 can sometimes cause a person to suddenly lose their sense of smell (anosmia) or taste (ageusia). This rarely occurs with flu, but it can occur with certain strains of the virus.
Flu: Flu does not typically affect a person’s sense of smell or taste, but otherwise has many symptoms similar to COVID-19 Rarely, as during the 1918 flu pandemic, a certain influenza strain does cause many people to lose their sense of taste or smell.
Treatment
While different treatments may be used for COVID-19 and the flu, both are treated by addressing symptoms, such as reducing fever. Severe cases may require hospitalization and very ill patients may need a ventilator — a machine that helps them breathe. For some patients, medications may help lessen the symptoms and shorten the duration of COVID-19 or flu.
COVID-19: Antiviral medications and other therapies are being tested to see if they can effectively address symptoms and shorten the duration of the illness.
Monoclonal antibodies are one such treatment, but need to be initiated early in the course of COVID-19. Contact your doctor as soon as possible after a positive COVID-19 diagnosis to see if you are eligible for monoclonal antibody treatment.
Currently, effective treatments are only available in an intravenous form, so they are not prescribed to patients outside of a healthcare setting.
Flu: Oral antiviral medications can address symptoms and sometimes shorten the duration of the illness. Because they are given by mouth, these antiviral therapies can be prescribed for patients who are not hospitalized as well as for those in the hospital.
Vaccine
COVID-19:Three types of COVID-19 vaccines have been approved or authorized for emergency use among specific age groups by the U.S. Food and Drug Administration (FDA). Johns Hopkins Medicine views all FDA approved or authorized COVID-19 vaccines as highly effective at preventing serious disease, hospitalization, and death from COVID-19.
Flu: A vaccine is available and effective in preventing some of the most dangerous types or to reduce the severity or duration of the flu. The flu vaccine is reformulated every year in anticipation of the influenza strains that are expected to circulate. It is very important to get vaccinated for the flu this year.
Complications
COVID-19: The development of complications, including long-term damage to the lungs, heart, kidneys, brain and other organs and a variety of long-lasting symptoms, is possible after a case of COVID-19.
Flu: Influenza complications can include inflammation of the heart (myocarditis), brain (encephalitis) or muscles (myositis, rhabdomyolysis), and multi-organ failure. Secondary bacterial infections, particularly pneumonia, can occur following a bout of influenza infection.
By Lisa Maragakis, M.D., M.P.H., senior director of infection prevention at Johns Hopkins, explains how the flu and COVID-19 are similar and how they are different.
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