There are three types of influenza viruses; A, B, C.
Influenza A includes the H1N1 and B viruses that cause seasonal epidemics of disease almost every winter in the United States. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics.
Definition: a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness. Flu signs and symptoms: Fever or feeling feverish, chills, cough, sore throat, runny or stuffy nose, muscle/body aches, and fatigue. It's important to note that not everyone with flu will have a fever.
Incubation: 1-7 days (viral shedding can begin 1 day before illness onset).
Exclusion: Exclude from school until fever free for 24 hours without the use of fever reducing medications.