Pontiac fever is a mild respiratory illness caused by the Legionella bacteria, which are commonly found in water systems. It is named after an outbreak that occurred in 1968 in Pontiac, Michigan. Symptoms typically include fever, chills, headache, and muscle aches, but the illness usually resolves on its own without treatment. Unlike Legionnaires' disease, which is a more severe form of infection caused by the same bacteria, Pontiac fever does not lead to pneumonia. Most people recover fully within a week or two. It primarily affects healthy individuals, but those with weakened immune systems may be at higher risk for complications.