The common term for the infectious agent that causes the flu is influenza virus. This virus belongs to the Orthomyxoviridae family and has multiple strains, with type A and B being the most prevalent in humans. The influenza virus can spread through respiratory droplets from coughs and sneezes. Symptoms of the flu include fever, chills, cough, body aches, and fatigue. Vaccination is a crucial preventive measure against the influenza virus, as it helps reduce transmission, severity of the illness, and complications associated with it.