Cough, fever, fatigue — what's causing it?

As cooler weather settles in, so does respiratory virus season — and many of the symptoms can look strikingly similar. Influenza (flu), respiratory syncytial virus (RSV) and COVID-19 are all contagious illnesses that affect the lungs and airways, but there are key differences in how they appear, spread and affect our health. 

Flu typically comes on suddenly. One day you may feel fine, and the next you’re hit with fever, chills, muscle aches, sore throat and fatigue. Most healthy adults recover in about a week, though older adults, pregnant women, and people with chronic conditions are at higher risk for complications like pneumonia. 

RSV is best known for causing severe illness in infants and older adults, though anyone can get it. In children, it may cause wheezing, difficulty breathing or poor feeding. In adults, symptoms can mirror a mild cold — cough, congestion, runny nose — but for those with heart or lung disease, RSV can become serious. 

COVID-19 symptoms vary widely. Some people have mild cold-like illness, while others develop fever, loss of taste or smell, fatigue, cough, or shortness of breath. COVID-19 can also lead to more serious complications, especially in older adults and people with underlying conditions. 

Because these viruses overlap in symptoms, testing is the only way to know for sure which one you have. The good news is that vaccines are available for all three, offering strong protection against severe illness. 

If you’re unsure whether to be seen, call your primary care practitioner. Early evaluation and testing can guide treatment — and help protect your family and community this respiratory season.