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| |  Water Disinfection Could Cut Legionnaires' Outbreaks LONDON, ENGLAND -- Jan. 22, 1999 -- Treating drinking water with a long-acting form of chlorine, called monochloramine, could significantly lower the number of outbreaks of the deadly lung infection known as Legionnaires' disease, report United States investigators in this week's issue of The Lancet. Legionnaires' disease was first identified in 1976 after an outbreak of a mysterious pneumonia among people attending a convention of the American Legion, a US veterans' group. Researchers now estimate that legionella species may be the third or fourth most common cause of community-acquired pneumonia. The fatality rate in outbreaks can run as high as 40 percent. The bacteria that cause disease, called Legionella, commonly live in lakes and streams in low numbers, but thrive in the slimy biofilm that forms inside pipes and water tanks. The bacteria spread to people when they inhale droplets of contaminated water from cooling towers, sprays and drinking water. Municipal water systems commonly use free chlorine to disinfect drinking water. Free chlorine kills bacteria quickly, but its effect is fairly short-lived. It often does not retain its bacteria-killing ability all the way to the tap and does not penetrate into the biofilm very well. Some municipalities add the slower-acting monochloramine, which better maintains its disinfecting power as the water travels through the water system and which can penetrate better into the biofilm where legionella and other microbes can hide. Dr. Jacob Kool and colleagues of the US Centers for Disease Control and Prevention compared the disinfection methods used by water systems that supplied 32 hospitals which had documented outbreaks of Legionnaires' disease with those supplying 48 hospitals which had not had outbreaks. "We found that hospitals supplied with water containing only free chlorine were 10.2 times more likely to experience an outbreak associated with drinking water," the investigators write. Assuming that about half of Legionnaires' cases are due to contaminated drinking water, the researchers calculate that routine treatment of municipal water systems with monochloramine could save between 900 and 2,025 lives each year in the U.S. alone. Related Links: The Lancet
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