What water conditions are best for growth of the organism?
• Warm, stagnant water provides ideal conditions for growth. At temperatures between 68° and 122°F the organism can multiply. Temperatures of 90°-105°F are ideal for growth. Rust (iron), scale, and other micro-organisms can also promote the growth of Legionella. • What common types of water are of greatest concern? • Water mist from cooling towers or evaporative condensers, evaporative coolers (swamp coolers), humidifiers, misters, showers, faucets, and whirlpool baths can be contaminated with the organism and if inhaled or swallowed can cause the disease. • Can Legionnaires’ disease be prevented? • Yes. Avoiding water conditions that allow the organism to grow to high levels is the best means of prevention. Specific preventive steps include: • Regularly maintain and clean cooling towers and evaporative condensers to prevent growth of Legionella. This should include twice-yearly cleaning and periodic use of chlorine or other effective biocide. • Maintain domestic water heaters at 140°F
