Legionellosis

Clear→ stable

Respiratory

Current NYS Status

799 cases in 2024 — near the 5-year baseline of ~680.

2024 statewide cases: 799

Source: NYSDOH Annual Communicable Disease Report 2024 + 5-yr baseline

What is it?

Legionellosis includes two diseases caused by Legionella bacteria: Legionnaires' disease (severe pneumonia) and Pontiac fever (milder flu-like illness). NYS reported 799 cases in 2024. Outbreaks are often linked to building water systems.

How it spreads

People get infected by breathing in small water droplets containing Legionella bacteria. Sources include cooling towers, hot tubs, decorative fountains, and large building plumbing. Not spread person-to-person.

Symptoms

Legionnaires' disease: cough, shortness of breath, fever, muscle aches, and headache — a serious pneumonia requiring medical treatment. Pontiac fever: milder, flu-like illness without pneumonia, resolving in 2–5 days.

Who is at risk?

Adults over 50, smokers, heavy drinkers, those with chronic lung disease, and immunocompromised individuals are at highest risk for Legionnaires' disease. Cases peak in summer and early fall.

What you can do

🛡Building owners: maintain water systems per ASHRAE 188 and NYC/NYS regulations

⚕️If pneumonia symptoms develop especially after travel or a hotel stay, tell your doctor — it changes treatment

⚕️Legionnaires' disease is treatable with antibiotics if diagnosed promptly

Tier B — Annual report tracking

Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.

Seasonality: summer

This information is for general public health awareness and is not a substitute for professional medical advice, diagnosis, or treatment.