Which type of virus is primarily responsible for the seasonal flu?

• A. Rhinovirus
• B. Influenza virus
• C. Coronaviruses
• D. Adenovirus

Answer: (B)

Seasonal flu is caused by influenza viruses. Each year, influenza A and B circulate and produce the abrupt fever, body aches, and fatigue that characterize the flu, which is why vaccines are designed to target these viruses. Other viruses can cause respiratory illnesses that resemble a cold or milder flu-like illness—rhinovirus mainly causes the common cold, coronaviruses can cause colds or more severe infections but are not the primary cause of seasonal flu, and adenovirus can also cause respiratory symptoms but does not drive the seasonal flu epidemics. So the influenza virus best explains the pattern and presentation of seasonal influenza.