Trending
Dear Dr. Roach: I've been hearing about Legionnaires' disease. What is it? How's it spread? Can it really be spread through windshield wipers? -- D.G.
Answer: Legionnaires' disease is a pneumonia caused by Legionella pneumophilia. It was first described in 1976, when an outbreak killed 34 people at an American Legion convention in Philadelphia. Since then, much has been learned about this condition.
Legionella live in soil and water, and water remains the most important source of infections in humans -- not from drinking the water but through aerosolized water. Air-conditioning cooling towers and water systems are the usual sources of large outbreaks, such as the one occurring as I write this in New York City.
There's (almost) no person-to-person transmission of Legionnaires' disease. Anyone can get Legionnaires' disease, but it's more common and more dangerous in older adults or those who have immune system diseases.
Legionnaires' disease can look like any other type of pneumonia, both clinically and in X-rays. However, people with Legionnaires' disease are more likely to have gastrointestinal symptoms such as nausea, vomiting and diarrhea. Some blood tests are more likely to be abnormal (low sodium levels, abnormal liver tests, and exceedingly high inflammatory markers).
Because Legionnaires' disease doesn't respond to some of the most common antibiotics, clinicians need to have a high index of suspicion for Legionella to use the effective treatments. (Clarithromycin, azithromycin and levofloxacin are the most commonly used treatments.) A culture or PCR test of what a person coughs up is very accurate at making the diagnosis; a urine test can be done as well.
It's true that windshield wipers can spread the disease. Legionella is commonly found in drinking water, and windshield wipers are very good at turning fluid into a fine spray. With windshield wiper fluid, there's not a chance of an infection. But tap water can have Legionella and lead to an infection if a person inhales the wiper mist when the reservoir's filled with tap water.
Readers may email questions to ToYourGoodHealth@med.cornell.edu.