Brian Labus, a senior epidemiologist at the Southern Nevada Health District, said the Centers for Disease Control and Prevention has not released the patient's name or when he or she died, the Las Vegas Sun reported Tuesday.
Health officials found Luxor water samples tested positive for Legionlla bacteria.
Gordon Absher, vice president of public affairs for MGM Resorts International, said super-heating and super-chlorinating water was used to kill the bacteria in the area where the deceased guest stayed, within a day the test results were confirmed, Absher said.
Within 10 days the hotel will undertake a voluntary remediation for the rest of the hotel, Absher said.
"We take this very seriously," Absher told the Sun said. "Health of our guests and our employees is of paramount importance to MGM Resorts."
The Luxor also developed a monitoring plan to prevent this from occurring, Labus said.
Last spring, two guests staying at the Luxor also became ill with Legionnaires' disease, but both recovered.
At the time, the health district collected bulk water samples for an environmental assessment, but no Legionella bacteria were detected, officials said.