Legionella Trends to Watch in 2026: Cooling Towers, Winter Operations, and Hidden Water System Risks

As we move into early 2026, one thing is clear: Legionella risk has not gone away, it has simply shifted back into familiar, but often overlooked, areas.

Across healthcare, commercial, and institutional facilities, recent public alerts and risk discussions continue to center on cooling towers, reduced-occupancy operations, and water system oversight gaps.

For facility leaders, infection prevention teams, and risk managers, this is a critical time to reassess water management practices and ensure systems are operating as intended not just documented on paper.

Cooling Towers Are Back in the Spotlight

Cooling towers continue to appear in Legionella investigations and public health advisories for a reason. They are uniquely capable of amplifying and dispersing aerosolized water over wide areas when controls fail or drift.

What we are seeing repeatedly is not catastrophic equipment failure it is incremental breakdowns:

• Inconsistent chemical control

• Missed inspections

• Incomplete documentation

• Unclear responsibility when readings fall outside limits

Even facilities with long-standing water management programs can be vulnerable if cooling tower oversight becomes routine rather than intentional.

Key takeaway: If your building has a cooling tower, it must be actively managed, monitored, and verified not assumed to be “handled.”

The Risk of “Winter Building Mode”

One of the most underestimated Legionella risk periods is low-use or transitional operations, which often occur during winter months. Common examples include:

• Reduced patient census or occupancy

• Temporarily closed wings or floors

• Seasonal temperature adjustments

• Less frequent flushing and system checks

These conditions promote water stagnation, temperature drift, and biofilm development, all of which create ideal environments for Legionella growth.

What makes this dangerous is that these changes are often viewed as temporary or operationally necessary and therefore go undocumented in the water management program.

Key takeaway: Any operational change that affects water use or flow should trigger a documented review of your water management plan.

Guidance Is Clear. Execution Is the Challenge

Industry guidance has matured significantly over the past several years. Resources from the Centers for Disease Control and Prevention, ASHRAE, and The Joint Commission all emphasize the same fundamentals:

• Know your water systems

• Identify where Legionella risk can increase

• Establish measurable control limits

• Monitor consistently

• Take corrective action when limits are not met

• Verify and validate that controls are effective

The challenge we see most often is not a lack of guidance, it is inconsistent execution and documentation across departments, vendors, and facilities.

A Practical Checklist: What Facilities Should Be Doing Right Now

Cooling Towers

• Confirm your water management plan explicitly includes cooling towers

• Verify inspection, cleaning, and treatment schedules are current

• Review who is responsible for escalation when readings fall outside limits

Domestic Hot and Cold Water Systems

• Identify low-use or seasonal areas and implement documented flushing protocols

• Confirm temperature control strategies are consistent with risk management goals

• Validate monitoring locations and frequencies

High-Risk Equipment and Areas

• Review devices that generate aerosols or use water (ice machines, therapy equipment, decorative water features)

• Confirm maintenance, monitoring, and cleaning procedures are current and recorded

Documentation and Readiness

• Update system descriptions when building use changes

• Ensure monitoring logs are complete and reviewed

• Maintain clear corrective action records

• Confirm verification and validation plans are defined and followed

These are the elements surveyors, leadership teams, and risk managers consistently focus on.

How Legionella Specialties Supports Facilities

At Legionella Specialties, we help healthcare and large facilities move beyond “check-the-box” compliance by focusing on practical, defensible water management programs that reflect how buildings actually operate.

Our approach supports:

• Clear system mapping and risk identification

• Real-world monitoring and control strategies

• Actionable documentation that stands up to surveys and audits

• Ongoing program support as buildings and operations change

Whether you are reassessing a cooling tower program, updating a water management plan, or responding to operational changes, the goal is the same: reduce risk before it becomes an incident.

Final Thought

Legionella risk rarely appears suddenly. It develops quietly through small gaps, overlooked changes, and assumptions that systems are “fine.” Early 2026 is the right time to look closely, ask hard questions, and ensure your water management program is actively protecting your facility, your staff, and the people you serve.

If you’d like help reviewing your current program or tailoring controls to your building type, Legionella Specialties is here to help.