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Another Healthcare-Associated Outbreak of Legionella Demonstrates Vulnerabilities

The CDC recently released a report regarding an outbreak of legionellosis, involving a hospital unit for immune compromised cancer patients. The report again demonstrates how vulnerable populations are at risk for healthcare-associated infections, including those from environmental exposures.

The Legionella outbreak was detected at an Inpatient Hematology-Oncology Unit at an Alabama hospital in May 2014. Patients were then examined to determine whether or not they had contracted the disease. Medical charts were reviewed, environmental assessments were conducted and water samples were tested in order to diagnose patients. Patients were diagnosed with hospital related legionellosis if they were radiographically-confirmed with pneumonia, tested positive for a positive urinary antigen and/or respiratory culture for Legionella and exposed to the hematology-oncology unit. Based on the extent of exposure during the incubation period, cases were classified as either definitely healthcare-associated or probably healthcare-associated.

Over a 12 week period, ten legionella cases, nine inpatients and one visitor, were identified. Six of these cases were deemed definitely healthcare-related and four were deemed probably healthcare-related. Environmental sampling revealed that Legionella pneumophila serogroup 1 (Lp1) existed in the potable water at 50% (17/34) of hematology-oncology unit sites, including all patient rooms tested; the three clinical isolates were identical to environmental isolates from the unit (mAb2-positive, sequence type ST36), thus confirming the causative linkage between the environmental isolates and the clinical specimens. No new cases of exposure occurred after implementation of water restrictions followed by point-of-use filters.

It was concluded that the likely source of the outbreak was the hospital’s contaminated potable water system with the Lp1 strain ST36.

Legionnaire’s disease (LD) is a form of pneumonia caused by exposure to the aquatic bacteria known as Legionella pneumophila.  LD develops 2-14 days after exposure and symptoms include fever, cough, shortness of breath, flu-like symptoms such as chills and body aches, and confusion or other mental changes.  LD is diagnosed by a medical provider and antibiotics are required for treatment. Fortunately, not everyone who is exposed to Legionella will develop the illness and the disease is not spread from person to person.

Typically, if Legionnaire’s disease is confirmed in a facility, a full scale investigation should commence. The expert response team of medical and environmental specialists can identify areas susceptible to the growth of Legionella, manage the incident, perform medical evaluations or surveillance activities (if necessary), conduct town hall meetings, and help create a remediation and preventive maintenance plan if Legionella source is found.

For more information on Legionella infections and resources for preventing, identifying or treating Legionella in your building’s water supply, please contact us at

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