Flu viruses are categorized into four types: A, B, C and D. Types A and B are the most harmful to humans and cause seasonal flu epidemics; in the Northern Hemisphere, flu season typically occurs ...

Alongside being rarer, it tends to cause more severe illness in children and often circulates later in the flu season, peaking in spring. Stock image of a man with the flu. Stock image of a man ...

In some cases, it can lead to death. Influenza A viruses cause seasonal flu epidemics almost every year in the United States. They can infect humans and animals. For more information and resources ...