How Likely Is It for Someone to Catch Legionnaire's from Windshield Washer Fluid?

Otto Schwake, PhD, Department of Civil and Environmental Engineering at Virginia Tech, explains how likely it is for someone to catch Legionnaire’s disease from windshield washer fluid.

Interview Transcript (slightly modified for readability).

“How likely would it be for someone to get Legionnaire’s disease from their car washer fluid? Long story short—not likely is what we think. Long version—maybe more likely than you would think. Legionnaire’s disease is a relatively common water-based, or water-borne, disease. We’re looking at anywhere between about 9,000 reported cases, but [it’s] heavily underreported, so in America, [it may be] somewhere between 20- and maybe 100,000 cases per year.

Now, because of topic, about Legionella in relation to cars and washer fluid, is still relatively un-researched, there’s not a lot of knowledge on how they’re in cars, period. Even less is known about how they’re getting to people or how [many] people become infected through this source. But there have been some studies to kind of attribute a measured level of risk. One relatively recent one, conducted by the state health department of New York, looking at Legionnaire’s disease cases in New York City over the last few years, attributed a risk value relatively high for professional drivers. Basically, after old age, smoking, and diabetes—the three major risk factors for Legionnaire’s—being a professional driver is one of the riskiest links to the disease. Again, that doesn’t really give you a number, right?

A more specific prediction came from a European study by the [United Kingdom] UK’s analog agency at the [Centers for Disease Control and Prevention] CDC. They did a big retrospective examination of Legionnaire’s cases in the UK, and eventually, through the study, came up with the prediction that about one fifth of community-acquired, sporadic cases, (so, cases not linked to hospitals, cases not linked to outbreaks) could be attributed to cars in some way. So, when you look at those numbers, okay, [it’s] one-fifth of a potentially small portion of Legionnaire’s cases. It’s tricky to say, but it definitely looks like it is something; it could be hundreds to thousands of cases in a big country like the United States. When you’re looking [at] risk factors, basically the more you drive, the more chances you have on a daily basis of interacting with washer fluid spray. Again, it’s a little premature to say how likely people are to get sick, but again, when you’re talking about a deadly disease, even a small risk, 1 in 10,000 or less, is still major from a public health standpoint.”