Seasonal Flu
Seasonal flu is caused by influenza viruses that infect humans each year. An estimated five to twenty percent of the population in the US contracts influenza each year.
Seasonal flu is characterized by the abrupt onset of fever, muscle aches, sore throat, and cough. It can lead to more severe disease, such as pneumonia. It can even cause death in infants and people who are very old or have chronic health problems.