Peer-reviewed studies indicate that drinking water systems are the primary source of Legionella bacteria. In addition, (+) The U.S. Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), U.S. Environmental Protection Agency (EPA) and the U.S. Veterans Health Administration (VHA) all list drinking water systems as primary sources of Legionnaires’ disease. Drinking water systems begin with source water and the public water treatment and distribution system which provides the supply water to our homes, schools, work places, and public buildings.
Since Legionella and other bacteria are naturally occurring in our source water, our public treatment facilities use safe levels of chemicals to eliminate them. However, bacteria also lives in the biofilm and corrosion that coats the interior walls of the pipes that carry water to our homes and directly to us. Under normal conditions, the bacteria remains in the biofilm. However, our public water systems are disrupted routinely by water main breaks, fire hydrant use, flooding, source water changes, new chemical treatments, and regular maintenance. When this happens, the biofilm where the bacteria lives is often released into the public water system where it can multiply in water storage towers and stagnate in low-flow areas and is then ultimately distributed downstream to our homes and buildings where we live.
The World Health Organization says that every year more than 3.4 million people die as a result of water related diseases, making it the leading cause of disease and death around the world (+).
Although the U.S. has one of the safest drinking water systems in the world, there are an estimated 4-32 million cases of acute gastrointestinal illness (AGI) per year from public drinking water systems (+).
According to the CDC, about 5,000 cases of Legionnaires’ disease are now reported each year in the United States. In general, the number of cases reported to the CDC has been on the rise over the past decade. This may reflect a true increase in the frequency of disease due to a number of factors including an older U.S. population, more at-risk individuals and aging plumbing infrastructure. It may also, in part, be a result of increased use of diagnostic testing.
While larger outbreaks get more media attention, the CDC concludes that only 4 percent of Legionnaires’ disease cases are part of known outbreaks. The remaining 96 percent are single, sporadic cases.
According to the CDC, more than half of Legionnaires’ disease outbreaks are caused by the drinking water. Exposure to Legionella bacteria most often occurs when exposed to contaminated water coming out of our faucets, shower heads, and even ice machines.
It means a more thorough investigation is needed to figure out how the bacteria got there and where else in the building and surrounding area it could still potentially be found.
The water used in cooling towers comes from the drinking water supply, is refreshed regularly and is typically treated by water management professionals on behalf of building owners. If incoming water contains bacteria, it can enter a cooling tower and in most cases the water treatment will neutralize it. The treatment used in cooling towers is designed for commercial and industrial use, and is far more potent to Legionella bacteria than what the public water utility can use to treat your drinking water supply. However, significant disruptions to the public water system can release large volumes of contaminants into a building and consume the chemical treatments—increasing the risk of bacterial growth.
This is why it is so crucial for state and local health departments to strictly follow the comprehensive testing protocols established by the CDC when investigating the source of any Legionnaires’ disease case. (+)(+)
The CDC offers guidelines and procedures on conducting an effective investigation. However, during an outbreak local public officials are often under pressure to assure residents that the threat has been resolved and typically limit their investigations to select water sources—such as cooling towers—due to the complexity of performing the full CDC investigation protocol. In addition, public officials can have difficulty taking accountability for issues they have with managing the public water system.
The best solution for preventing Legionnaires’ disease is reducing, and possibly eliminating, the Legionella bacteria in our public water system to prevent it from entering buildings and homes. As we work toward that goal, there are many methods to minimize and control Legionella bacteria in the water system. The first significant steps would be requiring a specified residual chlorine level throughout all points of the public system, performing periodic water chemistry testing, and public and customer warnings of water supply issues and upset conditions.
Other solutions include, but are not limited to, eliminating “dead legs” and stagnant water in the system, removing low flow shower heads and faucets, raising the temperature in hot water heaters, and educating homeowners and building owners on best water management practices. (+) Download more information in the resources section.
The risk of exposure to bacteria from our water systems increases significantly during events such as water system maintenance, water main breaks, nearby construction, water pressure changes, changes to water treatment, flooding and source water changes. However, few communities require water users to be notified in those cases. Making matters worse is the significant misinformation provided by authorities leaving residents confused or incorrectly believing there is no risk. Public notification practices need to improve, along with public education on how to best protect ourselves during periods of higher risk.
The CDC recently published a toolkit to help building owners develop a comprehensive water system management program to reduce the growth and spread of Legionella bacteria. The toolkit recognizes that every building’s water system is different and requires a water management program to be designed and implemented by multiple individuals involved with maintenance and water usage.
One major factor in a successful recovery from Legionnaires’ disease is a fast diagnostic test for it, after presenting to a primary healthcare provider. If you are exhibiting symptoms of Legionnaires’ disease—such as cough, fever, flu like symptoms—request to be tested. Treatment that starts immediately following the onset of symptoms is the most successful. When treatment is delayed, and for those patients who have compromised immune systems due to previous health problems, Legionnaires’ disease can result in prolonged hospitalization, complications and even death.