Wednesday, August 23 2006 15:35 Hrs (IST) - World Time -

New York: The cooling towers on top of many large commercial buildings hold a high number of infected amoebas that may pose a threat to human health, says a new study.

Sharon Berk and colleagues of Tennessee Technological University sampled 40 cooling towers in hospitals, universities and industries and 40 natural environments including lakes, rivers, creeks and ponds. They found infected amoebas in 22 of the cooling towers and only three in the natural samples.

They found infected amoebas in the cooling towers that could cause Legionnaires' disease, a severe form of pneumonia with fever, reported the Newswise wire.

The name Legionnaires' disease was coined in 1976 after a respiratory disease affected many delegates attending a convention in Philadelphia held by the American Legion of Pennsylvania.

Eventually, the bacteria that was responsible for the disease was isolated and named as Legionella pneumophila.

The results of the latest study published online by Environmental Science & Technology suggests these amoebas infected with bacteria are more prevalent in cooling towers than in natural environments.

People can contract pneumonia after inhaling Legionella in aerosol drifts from cooling towers, it said.

Researchers added that amoeba-associated micro-organisms, such as those found in cooling towers in the study, may be unrecognised causes of other respiratory diseases as well.