Influenza (noun)

1. An acute infectious disease caused by a virus and characterized by fever, headache, muscle pain, and severe fatigue.
2. A disease caused by a virus that affects the respiratory system, especially the nose, throat, bronchi, and lungs.
3. A contagious disease caused by a virus characterized by fever, headache, muscle aches, and a severe feeling of weakness.

Origin:

From italian influenza, from influire ("to influence"), from in- ("in") + fluere ("to flo.w")

Examples:

1. The flu is a common strain of influenza.
2. The influenza outbreak caused widespread illness and deaths.
3. The influenza vaccine is recommended for certain groups of people.
4. He caught influenza and was bedridden for a week.
5. Influenza can lead to serious complications, such as pneumonia.