The resort said six cases of the bacterial pneumonia were traced to the hotel and were reported to the federal Centers for Disease Control and Prevention in Atlanta, the Los Angeles Times reported.
All six were treated and fully recovered, said Stephanie Bethel of the Southern Nevada Health District.
Aria officials said guests who stayed at the resort from June 21 to July 4 might have been exposed to the bacteria, which spreads the disease.
The hotel said it detected "elevated levels" of the bacteria in several guest rooms -- a problem it said has been corrected.
"We will continue to monitor our water quality on an ongoing basis to ensure the safety of the water system and our guests," Paul Berry, vice president of hotel operations, told the Las Vegas Sun.
The illness got its name in 1976, when many of those attending a Philadelphia convention of the American Legion suffered from an outbreak, the CDC said.