Rising Legionellosis Rates in NYS

(June 1, 2026) The NYS Department of Health (DOH) has issued an advisory highlighting a notable increase in legionellosis across the state, underscoring the need for heightened clinical awareness and prompt public health response. After several years of stability, incidence rates rose in 2025 to 6.1 cases per 100,000 population, up from 4.1 cases per 100,000 between 2022 and 2024, signaling a meaningful shift in disease activity.

Legionellosis, caused by Legionella bacteria, includes Legionnaires’ disease, a severe form of pneumonia that cannot be clinically distinguished from other pneumonia etiologies without specific diagnostic testing. While cases occur year-round, NYS continues to see seasonal increases during the summer and early fall, consistent with conditions that support bacterial growth in water systems.

The advisory emphasizes the importance of maintaining high clinical suspicion, particularly in patients presenting with pneumonia where initial testing for common respiratory infections is negative. Providers are encouraged to utilize a combination of diagnostic approaches, including:

Respiratory culture
Polymerase chain reaction (PCR) testing
Urine antigen testing

Among these, culture remains the gold standard, as it is the only method that enables linkage between clinical cases and potential environmental sources. However, clinicians should note that Legionella culture requires specialized media and must be explicitly requested, which can be a critical gap in timely diagnosis if overlooked.

Public Health and Reporting Requirements

Prompt reporting remains essential for disease surveillance and outbreak prevention. DOH requires that:

All suspected and confirmed cases be reported immediately to the local health department (LHD) based on patient residence.
Cases in NYC be reported directly to the NYC Health Department Provider Access Line.
Cases in other regions of the state be reported to the local LHD or directly to the NYS Bureau of Communicable Disease Control if needed.

In addition, confirmed Legionella isolates must be submitted to public health laboratories (Wadsworth Center or NYC Public Health Lab).

For health care organizations, particularly long-term care and residential settings, the advisory reinforces the importance of:

Reviewing water management programs to mitigate Legionella growth
Promoting early diagnostic testing protocols among clinical staff
Ensuring that clear reporting pathways are understood and followed
Providing targeted education for frontline caregivers who play a key role in recognizing early symptoms

The increase in legionellosis rates in NYS represents a significant public health signal. Early recognition, appropriate diagnostic testing, and rapid reporting are essential to managing individual cases and preventing broader outbreaks. Health care leaders should ensure that both clinical teams and care staff are equipped with the knowledge and systems needed to respond effectively.

The advisory serves as a timely reminder that vigilance, particularly during peak seasonal periods, remains critical in protecting vulnerable populations and maintaining public health safety.

Contact: Carrie Mosley, cmosley@leadingageny.org, 518-867-8383 ext. 147