A 90-year-old Indiana woman has died from Legionnaires? disease after swimming in an Illinois hotel pool.

The woman, whose name and hometown has not been released, was one of two confirmed cases in the Lincoln, Ill., outbreak at a Best Western Inn.

The hotel closed its pool and spa by order of the Illinois Department of Public Health after they tested positive for a bacteria that causes Legionnaires? disease. Both confirmed cases were out-of-state guests. One stayed at the hotel in mid-January, and the other stayed in mid-February. Both were hospitalized and on ventilators.

Another 150 guests reported illness, but have not been confirmed. At least 900 former guests are being interviewed.

Investigators concluded the disease spread because there was no chlorine residual in the water. The state ordered the hotel to drain and clean the pool and spa, as well as change the filters.

Legionnaires? disease is contracted by inhaling mist or aerosol from a water source contaminated by the bacteria Legionella pneumophila. It is not communicable from person to person. The bacteria tend to grow in warm water, including hot tubs, large plumbing systems and air conditioning systems of large buildings.

Infection by the bacterium usually leads to Pontiac fever, but more severe versions cause pneumonia. The common symptoms include fever, chills and coughing. In addition, some patients experience muscle aches, headaches, fatigue, loss of appetite, and diarrhea. Most cases can be treated successfully with antibiotics.

In response to five reported Legionnaires? disease outbreaks in the United Kingdom between 2000 and 2005, the nation?s Health Protection Agency issued a new guidance for domestic and commercial owners of hot tubs. The agency stated that if owners and operators follow the set guidelines, they will prevent diseases such as Legionella from surviving in the water. In addition, operators should inform users of precautionary measures, which include showering before entering and not immersing their heads underwater.