Story highlights Water at Rio All-Suite Hotel and Casino tested positive for legionella bacteria

Guests who got sick stayed at the Las Vegas hotel in March and April

(CNN) Two recent guests at a Las Vegas resort have contracted Legionnaires' disease, officials said Friday.

The guests who contracted the lung infection stayed separately in March and April at the Rio All-Suite Hotel and Casino, the Southern Nevada Health District said.

Legionella, the bacteria that causes the disease, was found in the hot-water system of one of the hotel's towers during a test after the second illness was reported in late May, said Mark Bergtholdt, the district's environmental health supervisor.

The hotel is disinfecting the system with chlorine, Bergtholdt said. Guests were relocated from rooms served by that system, and those rooms won't be occupied until the system is properly flushed, he said.

Legionnaires' disease, a severe form of pneumonia, develops when people breathe small droplets of water infected with legionella bacteria, according to the Centers for Disease Control and Prevention.

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