Patient at Overlake diagnosed with Legionnaires’ disease

Illustration of Legionella pneumophila

Update (10.14.16)

Public Health – Seattle & King County confirmed that a King County resident who spent time in the Overlake emergency department on September 23 has tested positive for Legionella. The patient, a female in her fifties, experienced symptoms on September 29 and was hospitalized for Legionella pneumonia (Legionnaire’s disease) at another hospital.  She has been discharged from that hospital and is recovering. Because the patient was both in the community and at the hospital during the incubation period, it is not known whether she acquired Legionella at Overlake or elsewhere in the community.

In addition, Overlake has received preliminary positive findings from two environmental samples indicating Legionella in one sink and one ice machine, although it is not known whether it is the same species of Legionella as was found in either the recent case or the previous patient. The preliminary Legionella findings were not in areas of the hospital visited by the second patient. Species and molecular testing of samples from the initial patient and environmental samples is underway at the CDC.

Original post (9.26.16)

A patient at Overlake Medical Center has been diagnosed with a serious type of pneumonia
called Legionnaires’ disease caused by infection from Legionella bacteria. The patient is a male in his 60s with a medical condition that puts him at increased risk to infection. His health condition is reportedly improving.

Overlake reported the confirmed test results to Public Health on September 23, 2016. Based on when the symptoms first appeared, they have determined that the patient’s exposure to Legionella was at the hospital. Overlake is actively investigating the source by conducting an environmental assessment throughout their facility.

At this time there is no evidence to suggest any link between the Legionella case at Overlake and the recent Legionella cases at the University of Washington Medical Center.

Public Health is in the very early phase of our investigation. We are working closely with Overlake to determine if other patients may have been infected, to identify a potential source of the infections, and to address any ongoing risk. At this time, no additional cases of Legionella have been identified at Overlake.

Overlake is cooperating fully with this investigation and is taking appropriate steps to protect patient and staff safety, and to ensure that patients with pneumonia get appropriate laboratory testing.

What is Legionella?

Legionnaires’ disease is caused by breathing in small droplets of water that contain Legionella. It is not spread person-to-person.

source: CDC

Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams, and grows best in warm water. It can become a health concern when it grows and spreads in human-made water systems like hot tubs, hot water tanks and heaters, decorative fountains, cooling towers (such as those used in air conditioning systems), and large plumbing systems.

People can become infected with Legionella when they breathe in a mist that is contaminated with the bacteria. A Legionella infection can turn into illness affecting the lungs, and in some cases, it can cause Legionnaires’ disease.

Legionnaire’s disease is serious, but it can be treated with antibiotics. Most people who get sick need care in a hospital but make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease will die from the infection.

Who is at higher risk of getting sick?

Most healthy people do not get sick after being exposed to Legionella. People at increased risk of getting sick are:

  • People 50 years or older
  • Current or former smokers
  • People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema)
  • People with a weak immune system from diseases like cancer, diabetes, or kidney failure
  • People who take medications that suppress (weaken) the immune system (like after an  organ transplant operation or chemotherapy)

Public Health – Seattle & King County’s role in the investigation

Investigation of infectious diseases is part of the essential work of Public Health – Seattle & King County. In this incident, our role is to assist with the investigation and assessment of the extent of the problem, identification of a source of the legionella, and eliminate ongoing risk at the healthcare facility. We also provide information to the public about Legionnaire’s disease and on the findings and status of our investigation.

Learn more on Legionella from the CDC.


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I am a risk communications specialist at Public Health - Seattle & King County.