Stephanie Bethel of the Southern Nevada Health District told the Associated Press that this sometimes deadly form of pneumonia had been reported to the Centers for Disease Control and Prevention, and that the six guests had recovered.
The hotel sent letters to guests who had stayed at the Aria during the two-week period, saying that high levels of the bacteria legionella had been detected in several guest rooms. Recent additional testing showed no detectable levels.
In the past, air-conditioning systems, showers and hot tubs had been the suspected culprits in larger Legionnaires' outbreaks, but Nevada authorities have not yet determined the cause in this case.
"Legionella is a bacteria that lives in water and loves warm, wet environments," said Dr. Mary Nettleman, professor and head of the department of medicine at Michigan State University. "Unfortunately, people also like warm, wet environments, like hot tubs."
Last February, 200 partygoers at Hugh Hefner's Playboy Mansion in Holmby Hills, Calif., came down with flulike chills and high fevers. Four attending the DomainFest Global Conference there went on to develop a mild form of the disease, Pontiac fever.
David Castello was at that conference and described uncontrollable chills and a 102-degree fever: "I went from zero to not a good place in 15 to 20 minutes. It was like somebody flipped a switch."
Health authorities later suspected the mansion's whirlpool had been to blame for the spread of the bacteria.
Legionella transmission can occur through aerosols generated by air injected in the whirlpool, according to Dr. Amir Afkhami, assistant professor in the global health division at George Washington University School of Public Health.
"Basically, the bubbles that soothe can also become bubbles of infection by giving Legionella a piggyback ride into our respiratory system and allowing it to infect our lungs," she said.
Legionnaire's Killed Patient in New York Hospital
In 2005, a patient died at NewYork-Presbyterian/Columbia Hospital after being exposed to the bacteria at an in-patient center. The center later said the building's water supplies had been tainted.
Each year, between 8,000 and 18,000 Americans are hospitalized with Legionnaires' disease, according to the CDC. It tends to erupt during the summer and early fall months, and its fatality rate ranges from 5 to 30 percent.
The disease is caused by the bacteria, legionella pneumophila, which is found naturally in the environment and can thrive in warm water, like that in hot tubs, cooling towers, hot water tanks and large plumbing systems.
A simple culture test can reveal if a water source is contaminated. Antibiotics are used for treatment.
People can get the disease after breathing in the mist or vapor from the bacteria-ridden water. Those with weakened immune systems and lung disease, those who smoke, and the elderly are more susceptible to Legionnaires'.
The disease got its name in 1976 after an outbreak that sickened 221, killing 34, at a statewide American Legion convention at the upscale Bellevue-Stratford Hotel in Philadelphia. It was later determined the bacteria had spread through the air-conditioning system.
The negative publicity surrounding the disease forced the hotel to close that same year.
In 1977, Dr. Joseph McDade discovered a new bacterium, which was identified as the cause of the outbreak, and he named it legionella after the first victims -- Legionnaires.
Typically, Legionnaires' disease affects only a small number and cannot be transmitted person to person, according to Janet Stout, director of the Special Pathogens Laboratory in Pittsburgh.
"In outbreaks, [that's] usually less than 5 percent of the total number exposed," she said. "It appears from these reports that the rapid onset of symptoms is more typical of the related illness called Pontiac fever."
As for David Castello, who contracted the disease at the Playboy mansion, he rode out his illness until his fever broke five days later, but he weathered fatigue for weeks.
"This literally took away a week of my life," said Castello. "I just hope everyone else gets better quickly and we find out where it started."
For more information go to the Aria Resort and Casino website or call 877-326-ARIA (2742) or the Southern Nevada Health District hotline at 866-767-5038.