VERNON HILLS (CBS) — The number of cases of Legionnaires’ Disease at the Brookdale Vernon Hills senior living facility has increased to five, including one death, health officials reported Thursday.

Three cases, including one fatality, were reported earlier in February. Legionella bacteria were detected in one apartment, a pool filter, an irrigation system, and a decorative water fountain, officials said.

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Several preventative measures have been implemented at the Brookdale facility to prevent exposure to Legionella bacteria, including point-of-use filters. Thermal disinfection of the entire water system was performed last week, and hyperchlorination of the water system is scheduled. The pool and spa have been drained.

Legionnaires’ disease is a type of severe pneumonia caused by Legionella bacteria. It is treatable with antibiotics. Most people who get sick  make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease will die from the infection.

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Most healthy people do not get Legionnaires’ disease after being exposed to Legionella bacteria. People at increased risk of getting sick include:

People ages 50 years or older
Current or former smokers
People with a chronic lung disease
People with weak immune systems or who take drugs that weaken the immune system
People with cancer
People with underlying illnesses such as diabetes, kidney failure, or liver failure

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Legionella bacteria grow in areas of warm water. In order to be infected with the bacteria, a person must breathe in a mist or vapor that contains the bacteria. There is no evidence that the Legionella bacteria are spread from person-to-person.