What you need to know about Legionella

The name “Legionnaires’ Disease” was coined in 1976 after a respiratory disease affected many American Legion delegates attending a convention in Philadelphia.  Eventually, the bacteria that was responsible for the disease was isolated and named as Legionella pneumophila.  While we don’t hear about it with as much urgency as in 1976, it is still a significant public health threat.  Legionella is the leading cause of deaths from waterborne outbreaks in the United States and the rate of reported cases of legionellosis in the US has increased nearly 4-fold from 2001-2014 according to the Centers for Disease Control (CDC)

Legionella can thrive in warm stagnant water. The bacteria is commonly found in cooling towers that may be part of heating and air conditioning systems in hospitals, hotels and large buildings and may include showers and whirlpool spas. According to a study published by the CDC in December 2017, Legionella was isolated from cooling towers from seven of the eight US regions examined. 196 cooling towers were tested and 84% were positive for the bacteria in all seven of the regions tested.  The north central region of the US was not tested.

The transmission of Legionnaires’ disease is not completely understood. The normal presence of Legionella in water and soil is not automatically associated with an outbreak of the disease. It appears that the Legionella microbe must reach the lungs in order to produce the disease. Inhalation of small particles of contaminated water (aerosols) or soil seems to be the key.  According to the CDC study, the presence of sediment, nutrients, heterotrophic biofilm and amoebae in warm water combined with insufficient biocide treatment can result in growth of Legionella.   Evidence of person-to-person transmission has not been found. Therefore, attention has focused on the spread of Legionella by ventilation systems in buildings. When the circulated air picks up droplets of contaminated water, the bacteria can be transported throughout a building. If the droplets are small enough, they can be inhaled, thus providing a way for the bacteria to enter the lung.

The findings of the CDC indicate that under the right conditions, there is a potential for Legionnaires Disease outbreaks throughout the US. Maintain domestic water heaters at 40°F and water delivered at the faucet at a minimum of 122°F. Where these temperatures cannot be maintained, alternative controls such as biocides, ozone and ultraviolet treatments, should be used. The CDC study urges building owners to evaluate strategies to inhibit the growth of Legioinella in plumbing and cooling systems including diagnostic testing, use of temperature control, disinfectants, and maintenance of plumbing and cooling systems and development of a Legionella Water Management Program.  If you have any questions or need assistance in testing please contact The Cohen Group.