Atlantic Environmental, Inc.

Legionnaires’ disease (Legionella pneumophila)-sometimes deadly, sometimes not!

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Courtesy of Courtesy of Atlantic Environmental, Inc.

More than 90% of Legionella cases are caused by Legionella pneumophila, a bacterium that thrives in warm to hot water.  Pipes, tanks, faucets, showerheads, and hot water heaters are ideal breeding grounds for L. pneumophila.  Since infection with Legionella occurs through inhaling the bacterium, any activity in which contaminated water can be misted and subsequently inhaled can lead to infection.  Cooling towers, such as those used in large systems, as well as evaporative coolers, hot water systems, showers, whirlpool spas, decorative fountains, hot tubs, ice-making machines and room air humidifiers are all potential sources of Legionella.  Cruise ships, hotels, hospitals, nursing homes and office buildings are particularly susceptible.

Outbreaks of Legionnaires’ Disease usually occur in the summer and early fall.  The overall fatality rate from Legionella is from 5% to 30%.  However, the death rate among patients who contract the disease while they are already in the hospital for something else is close to 50% (, which corroborates the observation that most infections occur among the middle-aged or older, smokers, people on immunosuppressive therapy or corticosteroids, those who have had recent organ transplants and those with chronic pulmonary problems are also at elevated risk.  People who have weakened  immune systems from cancer, cancer treatments, diabetes and kidney failure are also more susceptible to infection with Legionella.

The first recognized outbreak of Legionnaires’ Disease occurred on July 27, 1976 during an American Legion convention in the Bellevue Stratford Hotel in Philadelphia, PA. Two hundred and twenty one (221) people were sickened with pneumonia, and 34 died. The U.S. Centers for Disease Control (CDC) finally isolated the causative agent: a previously unknown bacterium called Legionella pneumophila. The organism was found concentrated in the hotel’s A/C cooling tower, from which it was able to spread throughout the hotel.  (

It is difficult to diagnose Legionnaires’ Disease on the basis of symptoms or X-ray findings because its just like other forms of pneumonia.  Once we began looking for evidence of Legionella infections, especially with the urinary antibody test, we discovered that between 10,000 and 50,000 cases occur in the U.S. each year, and between 8,000 and 18,000 are sick enough to be hospitalized.  The Occupational Safety & Health Administration (OSHA) estimates that Legionellosis causes more than 25,000 cases and 4,000 fatalities each year (’-disease/DS00853/DSECTION&Prevention).  Nonetheless, the Centers for Disease Control, CDC, estimates that many more cases are either not diagnosed or not reported (

As many as 40% to 60% of tested cooling towers contained Legionella (CTI Legionellosis Guideline: Best Practices for Control of Legionella (WTP-148) (06)).  It is reasonable to assume a similar rate in other engineered water systems as well.  Water mists containing viable Legionella organisms can travel as far as 10 kilometers (6.2 miles).  The European Working Group for Legionella Infections (EWGLI) has published guidelines for recommended actions to take when water system test results show levels of Legionella (EWGLI: Technical Guidelines for Control of Legionella in Water Systems).  According to EWGLI, if a tested water supply system shows 1,000 Colony-Forming Units per milliLiter of water (CFU/mL), the system is considered to be under control.  If the test shows more than 1,000 CFU/mL, up to 10,000, EWGLI recommends immediate verification by re-testing.  If confirmed, do a risk assessment and identify remedial actions to be taken.  Above 10,000 CFU/mL, EWGLI recommends immediate re-testing followed by “shocking” the system with biocide, and implementing remedial actions for longer-term effect.

Some localities require regular Legionella testing in certain types of buildings.  The decision to test or not to test must be made on a case-by-case basis, taking into consideration such factors as potential for inhalation exposure, the age and general health status of those who might be exposed and the nature of the water system.

The professionals at Atlantic Environmental are well-versed and experienced in sampling for Legionella pneumophila.  We can assist you in setting up a risk assessment and sampling program to help you stay in control of your water system.  Call us at 800-344-4414 or e-mail at

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