COVID-19, RSV, and the seasonal flu have some symptoms in common.
COVID-19, RSV, and the seasonal flu are all respiratory infections, but they are caused by different viruses. COVID-19 is caused by the coronavirus SARS-CoV-2. RSV is short for respiratory syncytial virus, a type of pneumovirus. Influenza viruses cause the flu.
Fever, cough, and runny nose are symptoms common to all three illnesses, although not everyone gets a fever. Certain symptoms are more common with some of the viruses. For example, tiredness and achiness are more likely with COVID-19 and the flu. RSV and COVID-19 can cause shortness of breath or difficulty breathing, particularly in more severe cases. Other symptoms, such as decrease in appetite, tiredness, and irritability can be seen in babies under the age of 6 months with RSV infections.
Because these illnesses and others (including common colds caused by other viruses) have many symptoms in common, health care providers often make a diagnosis based on their knowledge about what virus is most common in a community at the time the patient is sick. When all three viruses are causing illness in a community at the same time, a diagnostic test can be used to identify which virus is the cause. This is typically done by testing body fluids collected with a nasal or mouth swab. If needed to support care, diagnostic tests are available in health care settings for all three viruses. Currently, easy-to-use at-home diagnostic tests are only available for COVID-19.