# 4645
In July of 1976, while many of us in the health care field were waiting for the expected arrival of a swine flu pandemic (see Deja Flu, All Over Again), another medical crisis was brewing at the Bellevue Stratford Hotel in Philadelphia.
This was the scene of the gathering of hundreds of veterans belonging to the American Legion, celebrating this country’s bicentennial. Within a couple of days of their arrival, scores fell ill with a serious flu-like illness.
At first, many believed this was the first arrival of the expected flu pandemic, but soon it became evident that this was something else entirely. But exactly what it was would take months to determine.
During this outbreak, 221 people were treated and 34 died.
It wouldn’t be until early in 1977 that a definitive cause would be isolated by the CDC – a Gram negative, aerobic bacteria found growing in the hotel’s air-conditioning cooling tower – that provoked a serious form of pneumonia.
Dubbed `Legionnaire's Disease’ by the press, this bacterium was named Legionella, and the pneumonia it produces Legionellosis.
While `discovered’ in 1976, Legionella had been with us, and causing serious illness, for a long time. It had caused earlier outbreaks, including one in Austin, Minnesota in 1957 (Osterholm et al., 1983) and at Saint Elizabeth’s Hospital in Washington, D.C. in 1965.
The cause of these outbreaks wasn’t identified, however, until retrospective studies were conducted after the Philadelphia outbreak.
We now know Legionella to be a major cause of infectious pneumonia, and that it sometimes sparks large outbreaks of illness. According to the CDC between 8,000 and 18,000 Americans are hospitalized with Legionnaire's Disease each year.
For more information on the disease, the CDC maintains a fact sheet at Patient Facts: Learn More about Legionnaires' disease.
The bacteria thrives in warm water, such as is often found in air-conditioning cooling towers, hot tubs, and even ornamental water fountains. Improper maintenance, or poor design, can lead to the bacteria blooming.
When water is sprayed into the air the bacteria can become airborne, and if inhaled by a susceptible host, can cause a serious (and sometimes fatal) form of pneumonia.
While large outbreaks of Legionella are often traced to specific causes, quite often the source of the infection for sporadic cases remains a mystery.
Yesterday we learned of a rather unique potential delivery system for Legionella – the windshield washer of your car.
This from the UK’s Health Protection Agency website.
Legionnaires’ disease
14 June 2010
A preliminary HPA study, published in the European Journal of Epidemiology, has found an association between not using screen wash in wiper fluid and the risk of contracting Legionnaires' disease.
More information:
Legionnaires' disease, caused by the legionella bacteria, is commonly linked to water systems such as air conditioning units, showers and fountains, where water is given off in a fine spray.
The case control study looked into the potential risk factors for drivers and passengers, given that most cases of sporadic, or isolated, Legionnaires' disease are rarely traced to a source, and that drivers figure disproportionately among cases of sporadic Legionella infection.
Researchers for the study interviewed 75 patients in England and Wales who had recovered from community acquired Legionnaires' disease between July 2008 and March 2009, comparing them to a group of matched people who had not experienced any similar infection.
The study found two exposures associated with vehicle use where there was an increased risk of Legionnaires' disease: driving through industrial areas and driving or being a passenger in a vehicle without screenwash in its wiper fluid. These associations had not been previously identified.
Further studies are now required to further explore this finding, and to determine whether the use of screen wash in wiper fluid could play a role in preventing this disease. The HPA is exploring ways of taking this forward with partner organisations.
You can read the study at: Windscreen wiper fluid without added screenwash in motor vehicles: a newly identified risk factor for Legionnaires' disease The European Journal of Epidemiology, 8 June 2010
Plain water in the wiper reservoir, kept warm and dark under the hood near the engine, is apparently conducive to the growth of Legionella. It can become aerosolized when you clean your windshield, and subsequently inhaled.
At least, that’s the operating theory of this paper.
`Screenwash’ is generally called `wiper fluid’ here in the US, and usually contains some form of antifreeze or alcohol. Those additives, investigators believe, are enough to inhibit the growth of this bacterium.
While more study is needed to pin down just how prevalent this mode of transmission really is (the authors suggest up to 20% of sporadic cases of Legionnaire's in the UK), this is a fascinating bit of detective work.
The Pump Handle posted more on this story last night in Legionnaires' Disease Linked with Wiper Fluid, including asking why – since this information has been known for months – it wasn’t announced sooner.
