Pontiac fever is caused by infection with bacteria from the genus *Legionella*, specifically the same bacteria responsible for Legionnaires’ disease but resulting in a much milder illness. The bacteria naturally live in water environments and can multiply under certain conditions, especially in warm water systems such as cooling towers, hot tubs, plumbing systems, and decorative fountains. When water contaminated with *Legionella* bacteria becomes aerosolized—turned into tiny droplets or mist—people can inhale these droplets, leading to infection.
The key factors that cause Pontiac fever include:
– **Presence of *Legionella* bacteria in water systems:** These bacteria thrive in warm water temperatures typically between 25°C and 45°C (77°F to 113°F). They can colonize building water systems, including hot water tanks, cooling towers, and plumbing pipes, especially if these systems are not properly maintained or disinfected.
– **Aerosolization of contaminated water:** When water containing *Legionella* is dispersed into the air as fine droplets—such as from showers, air conditioning cooling towers, whirlpool spas, or fountains—people nearby can inhale the bacteria. This inhalation is the primary route of exposure.
– **Environmental conditions favoring bacterial growth:** Lack of adequate disinfection, presence of biofilms (slimy layers inside pipes where bacteria can hide and multiply), and stagnant water all contribute to the proliferation of *Legionella* in water systems.
Once inhaled, the bacteria cause Pontiac fever, which is characterized by flu-like symptoms such as fever, muscle aches, headache, and fatigue, but notably without pneumonia. The incubation period for Pontiac fever is short, usually from a few hours up to two days after exposure. Unlike Legionnaires’ disease, Pontiac fever does not cause lung infection and typically resolves on its own within 2 to 5 days without the need for antibiotics.
In summary, Pontiac fever is caused by inhaling aerosolized water droplets contaminated with *Legionella* bacteria that have grown in warm, poorly maintained water systems. The bacteria’s ability to survive and multiply in man-made water environments, combined with aerosol generation, leads to human exposure and the onset of this mild respiratory illness.
