Legionnaires' disease spread by a paving machine

It was hard enough for health officials to track down the source of the original outbreak of Legionnaires' disease, at the old Bellevue Stratford Hotel in Philadelphia, in 1976.

Imagine if the disease had been caused by a moving target.

That's what happened last year in southeastern Spain, where researchers traced 11 cases to an odd source: tainted water in an asphalt paving machine.

The first two cases surfaced in the northern part of the town of Alcoi in July 2009, according to a paper in the September issue of Emerging Infectious Diseases.

But investigators could not find the disease-causing bacteria in any of the usual breeding grounds, such as showerheads, fountains or cooling systems for large buildings. Subsequent cases turned up elsewhere around town.

Then someone noticed that a paving machine had been used in an area where some patients lived. The machine had a water tank that generated a fine mist during operation. Could bacteria have been dispersed into the air and inhaled?

Sure enough, the water was found to contain Legionella pneumophila, and the strain was matched to samples taken from the patients. The problem arose in part because the machine did not use municipal water; it had been filled with spring water that was not treated with chlorine. One of the patients died, whereas the original outbreak, tied to an American Legion convention in Philadelphia, claimed 29 lives.

Robert Sharrar, an epidemiologist who helped crack the 1976 case, says he's never heard of an outbreak tied to a moving source before. But it makes sense, he says.

Now semiretired and a member of the city Board of Health, Sharrar says reading the new research brought back a few memories. Though the Spanish sleuths had the challenge of a moving target, at least the bacteria was already known to science.

The Philadelphia team, on the other hand, started from scratch.

The Europeans "had more tools than we did back then," Sharrar says. - Tom Avril