These three respiratory diseases, and others, share many of the same symptoms.
As winter approaches, many people wonder how to tell if they have a common cold, influenza (the flu), or COVID-19. All of these are caused by respiratory viruses and share some of the same symptoms, but they can lead to very different outcomes. Several other illnesses, such as respiratory syncytial virus (RSV) and mononucleosis (caused by the Epstein-Barr virus), can also cause similar symptoms.
The common cold can be caused by a variety of viruses, including rhinoviruses, coronaviruses, and adenoviruses. Typical symptoms include sore throat, nasal congestion (blocked or runny nose), sneezing, cough, and headache; fever is uncommon.
Influenza can also cause these symptoms, but it more commonly presents with fever or chills, fatigue, headache, and muscle or joint pain. Some people may experience gastrointestinal symptoms. Flu symptoms tend to come on more suddenly and are usually more severe than cold symptoms.
COVID-19 , caused by the SARS-CoV-2 coronavirus, can cause a wide variety of symptoms. Early variants of the virus typically caused fever, dry cough, and shortness of breath; a distinctive feature was the loss of the sense of taste or smell. However, newer variants of the virus cause symptoms more similar to those of a common cold, such as fatigue, sore throat, congestion, and headache. People who are vaccinated are more likely to have mild symptoms or be asymptomatic.
Testing is the only sure way to know which virus you have. Traditionally, people with mild to moderate cold or flu symptoms generally weren't tested, but COVID testing is recommended if you have symptoms. A PCR test administered by a healthcare provider offers the most accurate results, but self-administered rapid antigen tests are more convenient and less expensive.
Common colds usually resolve in about a week without treatment. Most people with influenza or COVID-19 recover within a few weeks, but these viruses can lead to serious complications. Older adults are more likely to develop severe influenza or COVID-19, while young children are more likely to develop severe influenza but are at low risk of severe COVID-19. Even people with mild COVID-19 can develop long-term symptoms known as long COVID.
People with a mild case of any of these illnesses can usually manage their symptoms at home with supportive care, including drinking plenty of fluids, getting enough rest, and taking over-the-counter medications. Seek medical attention if you or your child develop a high fever, have difficulty breathing, or experience other concerning symptoms. People at risk for more severe COVID-19 may be treated with Paxlovid or monoclonal antibodies.
Whatever you have, stay home and don't go to work or school, cover your mouth and nose when you cough or sneeze, and wear a well-fitting mask (like a KN95 or N95) to avoid spreading it to others. To reduce your risk of infection and severe illness, get a flu shot every year and stay up to date on your COVID-19 vaccinations and boosters.