Influenza, also known as the flu, typically occurs when the human body is infected by influenza viruses, leading to associated symptoms. The symptoms of influenza can vary depending on the type of infecting pathogen or virus. Influenza is primarily transmitted from person to person or through contact with livestock and poultry. The main route of transmission is through droplets, such as when one comes into contact with droplets from a sneeze or cough of an infected person. Another possibility is through contact with birds or livestock, such as being infected by secretions or excretions from pigs, which is also a mode of transmission.