The outbreak in the South Bronx has prompted a host of new measures to tighten oversight of cooling towers, boxy structures that sit atop roofs and regulate cold and hot air in buildings.

Legionnaires’ disease, often described as a severe form of pneumonia, is contracted by inhaling contaminated mist from water sources harboring Legionella bacteria. City health officials identified the hotel’s cooling tower as the source of the outbreak.

The Opera House Hotel on East 149th Street remained open throughout the outbreak, which claimed 12 lives and sickened more than 120 people, including two hotel guests, before city health officials declared it officially over last week. Juliet Forde and Helen Smith, who were checking out Wednesday afternoon, said they had not heard one word about the outbreak during their four-night stay.

An online reservation system showed the hotel was completely booked for this Saturday, and for four nights in September. Occupancy rates have hovered between 90 and 95 percent for the past two months, slightly higher than a year ago, the management said. Business has been, if anything, a little brisker. Not much else has changed at the hotel at the center of the worst outbreak of Legionnaires’ disease in the city’s history. Julio Vargas, the general manager, stationed himself downstairs in the wood-paneled lobby to explain to guests checking in that the cold air would return in a couple of hours. The Opera House Hotel had to turn off its air-conditioning one hot day this month so that a cleaning crew could scrub away the Legionella bacteria lurking in the cooling tower on its roof.

Opera house hotel