NEW YORK, Aug. 4 (UPI) -- The death toll from an outbreak of Legionnaires' disease in New York City has risen to 7, with a total of 81 confirmed cases of the water-borne bacteria infecting people.
Investigators tested 22 air-conditioning cooling towers, finding five that tested positive for the Legionella bacteria. The towers at Lincoln Medical and Mental Health Center, the Concourse Plaza Mall, the Opera House Hotel, a Verizon office building, and the Streamline Plastic Co. were all disinfected and are expected to be tested again Tuesday for the bacteria.
"We hope that there are no more cases, and certainly hope no more deaths, but do expect additional cases simply because there could be people who may have been infected before the cooling towers were cleaned," Dr. Jay Varma, deputy commissioner for disease control, told NBC News. "The bacteria has an incubation period. It can be as long as 10 days between infection and disease."
The outbreak has resulted in 81 people contracting the disease, 64 of whom were hospitalized. Officals told CBS News 28 of those individuals have been released from the hospital.
Legionnaires' disease can cause chills, fever and a cough, as well as an upset stomach and neurological effects, but largely causes minor symptoms. The disease can be dangerous for those with weakened immune systems, however.
The towers that have been cleaned -- Varma said bleach and other chemicals are applied to the tower surfaces and then scrubbed clean by hand -- would be checked again Tuesday. It takes at least 24 hours to clean the towers, and can be difficult because of their size and shape
"We don't know how the towers get contaminated in the first place," Varma said. "We know bacteria can live in the environment, but don't know why some are more likely to be contaminated than others. One explanation is that the chemical treatment systems to maintain them do not function well."
The number of Legionnaires' cases has tripled during the last decade, from 73 in 2004 to 225 in 2014, leading New York City Mayor Bill de Blasio to announce yesterday that he plans to announce new recommendations for the city to better prevent the cultivation and spread of the bacteria.
"A more systemic solution is required to prevent the cycle of these outbreaks from continuing," de Blasio said in a statement. "This week, new legislation will be announced designed to halt future outbreaks of Legionnaires', and place new emphasis on long-term prevention. The comprehensive package will address inspections, new recommended action in the case of positive tests, and sanctions for those who fail to comply with new standards."