The flu can also cause a general feeling of fatigue or malaise, Ray says, as well as gastrointestinal issues like diarrhea and nausea, especially among children. As with COVID, some people also experience a loss of taste and smell with the flu, he adds.

Flu A and flu B are two different strains of influenza, explains Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York. There are actually four different types of flu—A, B, C, and D—but A and B are the strains that fuel flu season each year, per the CDC.