The state of New York led the nation last year with 1,009 cases of Legionnaires’ disease reported to the Centers for Disease Control and Prevention (CDC) – despite stricter state regulations meant to protect against the proliferation of Legionella bacteria in cooling towers, hospitals, and residential health-care facilities.

More than 40 percent of cases – a total of 441 – were reported in New York City in 2017, a 65 percent increase over 2016.

The state total was a 38 percent increase over 2016, and the NYC count was more than even 2015, the year of the worst outbreak in city history: 133 Bronx residents were sickened, and 16 people died.

“Unfortunately, we continue to see cases of Legionnaires’ disease climb in New York,” said Daryn Cline, a spokesperson for the Alliance to Prevent Legionnaires’ Disease (APLD), in a news release. “This is especially troubling since New York is holding itself out as the leader in Legionnaires’ disease prevention. The truth of the matter is their emphasis on water management inside the building has not had an impact on decreasing the rate of disease.”

The Alliance has been critical of regulations that were put in place after the Bronx outbreak in 2015. The APLD contends the regulations are too narrowly focused on building equipment and do not address the root problem: the public water supply and its distribution system, which is how bacteria infects buildings and cooling towers.

“The most important thing to remember is that Legionnaires’ disease is a waterborne illness, so water must be the focus of any preventive measure,” Tonya Winders, president and CEO of Allergy & Asthma Network, was quoted in the release. “Any solution that doesn’t address the bacteria entering our homes and buildings from the public water supply and distribution system is not a solution at all.”

Another key criticism of New York’s current approach is the failure to address individual cases of Legionnaires’ disease, which — according to the CDC — make up approximately 96 percent of the total recorded cases nationally. By focusing only on building equipment, New York’s regulations address only a portion of the 4 percent of cases attributed to outbreaks, leaving New Yorkers at continued risk of infection.

“Our public policies are being driven by outbreaks which generate news and political pressure,” Cline said. “There were only two known events in New York City that were classified as outbreaks in 2017, with the highest infecting 13 people. Yet, in 2017 an average of 19 people contracted Legionnaires’ disease each week across the New York state. During one week alone, there were 27 new cases in New York City, which went largely unnoticed. Worse yet, they were not fully investigated to understand the sudden spike or how to prevent similar spikes in the future.”

Warmer temperatures to blame?

Legionnaires’ disease – a severe type of pneumonia or lung infection – is “an emerging disease in the sense that the number of recorded cases of Legionnaires’ in the United States continues to increase,” said Laura Cooley, MD, MPH from the Respiratory Diseases Branch of the CDC.

Cooley said the increase is due to a rise in the susceptibility of the population, with more and more people on immunosuppressive medications. In addition, there could be more Legionella in the environment, with warmer temperatures creating the right conditions for bacterial growth. The last three years have been the hottest years on record, with NASA ranking 2016 as the warmest and 2017 second-warmest.

About 25,000 cases annually

The CDC estimates that 25,000 cases of Legionnaires’ disease occur in the U.S. yearly. Only 5,000 cases are reported, however, because of the disease’s non-specific signs and symptoms.

Legionella bacteria are contracted by inhaling microscopic water droplets (mist or vapor). The bacteria, which thrive in warm water, are found primarily in human-made environments, such as cooling towers and air-conditioning systems, to name two.

Cases are more commonly reported during the summer and early fall but can happen any time of the year.