What type of pathogen is responsible for causing influenza, a respiratory illness?

 A pathogen is a microorganism or other agent that can cause disease in a host organism. Influenza is a respiratory illness that is caused by a virus. In particular, influenza viruses A, B, and C are responsible for causing influenza in humans. Influenza viruses are highly contagious and can spread through the air when an infected person talks, coughs, or sneezes. Symptoms of influenza can include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, and fatigue. Bacteria, fungi, and parasites can also cause respiratory illnesses, but they are not responsible for causing influenza.