KING COUNTY, WA - Legionnaires' Disease (LD) refers to pneumonia caused by legionella bacteria. Legionella longbeachae is an uncommon type of legionella that causes a small proportion of legionella infections. Each year in King County there are one or two cases of infection reported due to Legionella longbeachae. Recently, the first cases of Legionnaires' Disease associated with potting soil use in the US were reported, including one case from King County.
Legionnaires' Disease usually occurs in persons with underlying medical conditions, especially chronic lung disease, smokers, elderly persons, or in persons with weakened immune systems. It is unusual for healthy persons to get Legionnaires' Disease. Persons become ill 2-10 days after exposure to the bacteria. Symptoms include fever, muscle aches, headache, weakness, cough, shortness of breath and sometimes confusion and diarrhea. The infection does not spread from person-to-person. Although outbreaks of Legionnaires' Disease sometimes occur, most cases are not associated with outbreaks and the source of infection remains unknown. At this time there is no outbreak of Legionnaires' Disease in King County.
Legionella bacteria are found widely in the environment, especially in naturally occurring bodies of water. The association between infection with Legionella longbeachae and potting soil use was recognized in Australia in the 1980's. Potting soil appears to provide an environment in which Legionella longbeachae can grow. In studies from Australia, the bacteria have been found in potting soils from a variety of manufacturers.
The risk of acquiring Legionnaires' Disease from potting soil appears to be extremely low. Because this is a newly identified problem, formal recommendations regarding the risk of Legionnaires' Disease associated with potting soil use are not available. Health officials in Western Australia have issued guidelines that may reduce the risk of acquiring Legionnaires' Disease among persons using potting soil. Persons using potting soil and who wish to take precautions that may reduce the very small potential risk of illness even further may consider the following recommendations:
- open potting mix bags with care to avoid inhaling airborne potting mix,
- moisten the contents of the bag on opening make a small opening and insert a garden hose to dampen the potting mix
- wear gloves to avoid transferring potting mix from hand to mouth,
- always wash hands after handling potting mix, even if gloves have been worn,
- and take the same precautions when handling soil, peat, mulch and garden composts.
More information about Legionnaires' Disease is available at the Centers for Disease Control and Prevention website: http://www.cdc.gov.
