The number of Legionnaires’ disease cases has jumped nearly 400 percent in the last 15 years, with more than 20 outbreaks a year in the United States — and the Centers for Disease Control and Prevention (CDC) has issued new guidance and tools for preventing this deadly pneumonia.

People with asthma or COPD are at increased risk from Legionnaires’ disease, a life-threatening condition usually caught by breathing droplets of contaminated water in large building systems such as apartment buildings, hospitals, hotels, long-term care facilities and cruise ships. Droplets may become airborne in showers and faucets, cooling towers, hot tubs, decorative fountains or other sources. The bacteria can also be spread through nebulizers not cleaned thoroughly or that use contaminated tap water.

The bacteria is present all around in the environment, but it grows to dangerous levels in stagnant, warm water. CDC’s water management program toolkit reflects best practices for preventing its growth.

The recently launched provides additional information about the Legionella bacteria, its source, how people can become infected with Legionnaires’ disease, symptoms of the condition, and ways to prevent the bacteria from spreading.