You may be harboring the dreaded Legionnaires Disease in your water pipes and home. The bacteria can grow in the slimy gunk lining the pipes and this may be the cause of about 20% of the cases.

“The evidence suggests that the residential water system is an underappreciated source of Legionnaires disease,” says microbiologist Janet Stout.

Daniel Q. Haney writes that Stout thinks between 2 and 5% of the 600,000 pneumonia cases requiring hospitalization in the U.S. each year are caused by the Legionella pneumophilia bacteria. The diagnosis is often missed because it requires both a bacterial culture and a special urine test.

She tracked down the sources of Legionnaires disease in parts of Pennsylvania and Ohio and tested the patients’ home water. She found the Legionnaires bug in 24% of their water pipes. Two of the patients eventually died.

People catch the germs by inhaling drops of water when they shower or wash dishes. Most people exposed to the bacteria never get sick, but those with weakened immune systems are vulnerable. “The overall perception we have that drinking water in the home is free of bacteria is a misconception,” says Stout. “Although Legionnaires is a naturally occurring organism in water, people should be aware this is a potential source of disease.”

People keep the temperature in their hot water tanks low to save on electricity and prevent scalding. But you should turn up the temperature to above 140 degrees at least occasionally, then run hot water from all faucets and showers for half an hour, in order to kill off any bugs living in your pipes. This should be done every two or three months. You should also let the shower run on hot for a few minutes, before adjusting it and starting to bathe, so some of the bacteria will flush out of the pipes.

“Everybody has been so focused on hospitals,” says microbiologist Richard Miller. “Homes have always been in the background, but they are clearly a risk factor.”

Keep up on the wonders?and dangers?uncovered by modern science with Linda Moulton Howe, who reports on Dreamland every week.

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