Thursday, January 26, 2006
Airborne legionnaires bacteria can travel miles
By Anne Harding
NEW YORK (Reuters Health) - The bacterium responsible for causing legionnaires disease can spread up to 6 kilometers from its source by airborne transmission, French researchers report.
Legionella pneumophila likes to live in hot water, such as in industrial cooling towers or the water systems of large buildings where it can then cause pneumonia-like infections. Now it seems that a wider area may be at risk.
Past studies found airborne legionella spread only a few hundred meters, lead author Dr. Tran Minh Nhu Nguyen, who is currently at the National Public Health Institute in Helsinki, told Reuters Health. If other investigators confirm the new findings, he added, "a number of regulations and guidelines related to this environmental health risk should be revised accordingly."
In the Journal of Infectious Diseases, Nguyen and his team report on their investigation of a 2004 outbreak of legionnaires disease that occurred in Pas-de-Calais in northern France.
They identify a contaminated cooling tower at a petrochemical plant as the source of the outbreak, which killed 21 of the 86 individuals with laboratory-confirmed infection. Most of the victims lived within 6 kilometers of the plant, although one lived 12 kilometers away.
The fatality rate is "striking" when compared with past community-acquired outbreaks, in which fatality rates ranged from1 percent to 11 percent, the researchers note. They think the strain of legionella involved could have been unusually virulent.
The outbreak occurred in two peaks, the first ending after the cooling tower had been shut down and the second beginning during cleaning of the tower and peaking once it had reopened.
The pattern suggests that high-pressure cleaning methods used to decontaminate the towers contributed to the bacterium's spread. "There are measures and guidelines for managing cooling towers contaminated with legionella," Nguyen said. "However, how well they have been adopted and implemented depends on the individual country and setting."
SOURCE: Journal of Infectious Diseases, January 1, 2006.