HHS Warns North Carolina of Rising Legionnaires' Disease Cases

On April 17, 2026, the North Carolina Department of Health and Human Services issued a public advisory warning that Legionnaires' disease cases had risen sharply across the state — 310 confirmed cases in 2025, up from 201 the year before [1]. The 54% year-over-year jump far exceeded the state's recent baseline of roughly 200 cases annually [2]. The advisory included prevention guidance for homeowners, healthcare facilities, and commercial building operators, but stopped short of imposing new mandates or allocating emergency funding.

The announcement arrived during the early weeks of the warm season, when conditions for the waterborne bacterium Legionella pneumophila become most favorable. But the deeper story stretches well beyond one state's case count: Legionnaires' disease has been climbing across the United States for more than two decades, yet the public health response remains fragmented, voluntary compliance dominates regulation, and experts estimate the reported numbers capture only a fraction of actual infections.

The Numbers: North Carolina and the Nation

North Carolina's 310 cases in 2025 represent the state's highest annual total on record [1]. For context, the 2014–2018 period averaged approximately 200 cases per year [2]. The increase is consistent with a broader national pattern: CDC data show that reported U.S. Legionnaires' cases rose from about 1,100 in 2000 to a peak of 9,933 in 2018 — a more than sixfold increase in crude incidence, from 0.42 to 2.71 per 100,000 population [3].

Source: NCDHHS

Data as of Apr 17, 2026CSV

Cases dipped during the first year of the COVID-19 pandemic, when buildings sat empty and fewer people were exposed to contaminated water systems, but rebounded to an estimated 7,500 cases in 2021 [3]. About 95% of patients require hospitalization, and roughly 10% die [3].

Source: CDC

Data as of Jan 1, 2024CSV

North Carolina's incidence rate, given the state's population of approximately 10.8 million, works out to roughly 2.87 per 100,000 for 2025 — slightly above the most recent national average of about 2.71 per 100,000 [3][1].

What Is Legionnaires' Disease?

Legionnaires' disease is a severe form of pneumonia caused by Legionella bacteria, which thrive in warm freshwater environments. People contract it by inhaling contaminated water droplets or mist — not through person-to-person contact [1]. Common sources include cooling towers on large buildings, hot tubs, decorative fountains, showerheads, and faucets, particularly in buildings where water sits stagnant for extended periods [4].

The disease was first identified after a 1976 outbreak at an American Legion convention in Philadelphia. Today it is a nationally notifiable disease, meaning states are required to report confirmed cases to the CDC [3].

No Single Source: A Statewide Pattern

Unlike some prior outbreaks, the 2025 surge in North Carolina has not been traced to a single facility or water system. The NCDHHS advisory described the increase as "statewide," suggesting dispersed environmental exposure rather than a point-source event [1].

This stands in contrast to the state's most significant prior outbreak: the 2019 North Carolina Mountain State Fair incident. That event, linked to hot tub displays at the Western North Carolina Agricultural Center in Fletcher, infected 136 people, hospitalized 96, and killed four [5]. It was the largest hot tub-associated Legionnaires' outbreak ever recorded worldwide [6]. An investigation found that case patients were significantly more likely to have walked past the hot tub displays, where aerosolized contaminated water spread through the exhibition hall [6].

The absence of a single identified source in the current rise makes the public health response more complicated. When a specific cooling tower or water feature is identified, remediation is straightforward — shock the system with biocide, replace components, resume operations. A diffuse increase across a state with more than 10 million residents suggests systemic conditions favoring bacterial growth: aging pipes, buildings with intermittent occupancy, and inadequate water temperature management across thousands of individual systems.

The Undercount Problem

The 310 cases reported in North Carolina may substantially understate the actual burden. A landmark report by the National Academies of Sciences, Engineering, and Medicine estimated that reported Legionnaires' cases underrepresent the true incidence by a factor of eight to ten [7]. Applied nationally, that would place the actual annual case count somewhere between 52,000 and 70,000, compared to the roughly 10,000 reported in a typical recent year [7].

Several factors drive this gap. The most commonly used diagnostic test, the urinary antigen test (UAT), detects only L. pneumophila serogroup 1 and has a sensitivity of approximately 80% even for that strain [8]. The test can also return false negatives early in the disease course [8]. Most hospitals do not routinely culture sputum for Legionella, and professional guidelines have historically discouraged routine testing of all hospitalized pneumonia patients [7]. Only about 25% of acute-care hospitals conduct the urinary antigen test on-site [7].

No publicly available data specify what share of North Carolina's pneumonia hospitalizations were tested for Legionella during the 2025 reporting period. The NCDHHS advisory did not address testing rates. But given the national pattern — where 96% of individual cases are never investigated for their environmental source [7] — the gap between reported and actual cases is likely significant.

Dr. Erica Wilson, medical director of the medical consultation unit in the NCDHHS Division of Public Health, acknowledged the ongoing risk. "To prevent it, you need to keep things flushed, so your faucets, showers, garden hoses. Keep your hot water heater above the temperature where it likes to grow," she said in a statement accompanying the advisory [9].

Who Is Most at Risk?

Legionnaires' disease does not affect all populations equally. National surveillance data show that 63.5% of cases occur in men, and the median age of patients is 60 [3]. People over 50, current or former smokers, and those with chronic lung disease, diabetes, kidney failure, cancer, or compromised immune systems face elevated risk [10].

The most striking disparity is racial. CDC data from 2000–2018 show that Black or African American individuals had an incidence rate of 5.21 per 100,000 in 2018, compared to 1.99 per 100,000 among white individuals [3]. The relative increase from the 2000 baseline to 2018 was 11-fold among Black Americans — the steepest climb of any demographic group [3].

Researchers have linked this disparity to social determinants rather than biological susceptibility. Areas with higher poverty rates, more vacant housing, more renter-occupied homes, and structures built before 1970 show higher Legionnaires' incidence [11]. Aging water infrastructure in disadvantaged neighborhoods creates conditions — corroded pipes, low water pressure, stagnant sections of plumbing — where Legionella flourishes [11]. Black Americans also have higher rates of diabetes, end-stage renal disease, and certain cancers, all independent risk factors for Legionnaires' [11].

North Carolina's advisory did not break out case demographics by race, age, or county. That data, when released, could reveal whether the state's disparities mirror the national pattern.

The Cost of an Outbreak

Legionnaires' outbreaks carry substantial financial consequences that extend well beyond medical bills. Hospitalization for Legionnaires' disease typically lasts 2 to 14 days, and survivors may experience lasting respiratory complications [10]. Legal settlements in Legionnaires' cases have ranged from $225,000 to $5.2 million per plaintiff, with jury awards reaching as high as $6 million [12]. In one extreme case, a 2006 jury returned a $193 million verdict against a manufacturer of spa equipment used on a cruise ship, though much of that figure reflected business interruption losses [12].

When an outbreak strikes a commercial property, the operational costs compound rapidly. A 2009 outbreak at a Miami hotel reportedly caused revenue losses of $200,000 per day during the closure required for remediation [13]. Building owners face increased insurance premiums, emergency remediation expenses, potential loss of tenants, and reduced property values [13].

Who pays depends on ownership. When the source is a private facility — a hotel, hospital, or apartment building — the property owner bears primary liability and remediation costs. When a public water system is involved, the financial burden shifts to the utility and, by extension, ratepayers and taxpayers. In either case, public health investigation costs are borne by state and local health departments, which often lack dedicated Legionella investigation budgets [7].

Regulation: A Patchwork of Voluntary Measures

The CDC has recommended since 2017 that buildings at increased risk develop Water Management Programs (WMPs) based on industry standard ASHRAE 188 [4]. These programs require identifying hazardous conditions in building water systems — dead-end pipe runs, storage tanks, cooling towers — and implementing controls such as temperature management, disinfectant monitoring, and routine testing [4].

But in most jurisdictions, WMP adoption remains voluntary. There is no comprehensive federal law governing Legionella in building plumbing. The Safe Drinking Water Act's jurisdiction ends at the property meter, leaving the internal plumbing where most bacterial growth occurs outside federal regulation [14].

North Carolina is one of a handful of states that has acted legislatively. The state's Legionnaires' Disease Prevention Act (House Bill 909) requires building owners to establish water management plans consistent with ASHRAE 188, including validation testing by state-approved laboratories [15]. Covered buildings were required to have plans in place by October 1, 2022, and owners must retain sampling results for at least three years [15].

However, the law's enforcement mechanisms and the actual compliance rate remain unclear. The NCDHHS advisory issued in April 2026 was advisory in nature, with no new enforcement powers or emergency funding attached [1].

The Centers for Medicare and Medicaid Services (CMS) has imposed its own requirements since 2017: Medicare-certified hospitals, critical access hospitals, and long-term care facilities must develop and implement WMPs or risk losing Medicare and Medicaid certification [16]. But the CMS directive focuses on process management — documenting that a plan exists and is being followed — rather than requiring direct Legionella testing [16]. A facility can be technically compliant without ever having cultured its water for the bacterium.

By contrast, the Department of Veterans Affairs has required quarterly Legionella testing of at least 10 outlets per building since 2014 under VA Directive 1061 [14].

How Other States Compare

New York enacted some of the strictest Legionella regulations in the country after a 2015 outbreak in the South Bronx killed 12 people. The state requires mandatory registration and quarterly Legionella sampling of all cooling towers, and healthcare facilities must have culture-based sampling plans. A positivity rate above 30% triggers mandatory control measures and state notification [17].

Illinois passed Public Act 102-0004 in 2021, requiring hospitals and nursing care facilities to create Legionella testing policies [17]. Virginia mandated water management plans for public schools starting in July 2021 [17]. California has enacted legislation requiring water quality assessments for state-owned buildings and public schools, with 24-hour health department notification if Legionella levels exceed 1,000 colony-forming units per milliliter [17].

North Carolina's HB 909 places the state ahead of the majority of states that have no Legionella-specific legislation, but behind New York's more prescriptive testing and notification requirements.

Structural Barriers to Prevention

Several systemic factors work against reducing Legionnaires' cases, and stakeholders disagree about solutions.

Plumbing codes and low-flow fixtures. Modern water conservation fixtures reduce flow rates, which extends the time water sits in pipes — precisely the stagnant conditions that favor Legionella growth. Plumbing codes written 50 years ago sized pipes for higher-flow fixtures, creating oversized distribution systems in buildings retrofitted with low-flow alternatives [14]. Some building codes mandate delivering water at 85–110°F, which falls within the optimal temperature range for bacterial growth [14].

Temperature conflicts. The most effective measure against Legionella is maintaining hot water above 140°F in storage and above 120°F at points of use [16]. But anti-scalding regulations in long-term care facilities create tension: CMS guidance on preventing scalding injuries can conflict with the temperatures needed to suppress bacterial growth. The result is ambiguous compliance requirements that leave building operators uncertain about which standard takes precedence [14].

Cost of compliance. Building owners, particularly those operating older commercial or residential properties, argue that retrofitting plumbing systems, installing secondary disinfection, and conducting quarterly testing impose significant costs without guaranteed return [14]. Buildings that install supplemental disinfection systems may be classified as "consecutive water systems" under the Safe Drinking Water Act, triggering additional federal compliance obligations that can be prohibitively expensive [14].

Public health capacity. Many state public health laboratories lack the resources to identify, quantify, or subtype Legionella in water specimens [7]. Legionellosis programs receive low priority compared to other preventable infectious diseases, and reimbursement practices discourage ordering the microbiologic diagnostic tests that would improve case detection [7]. U.S. reporting delays also far exceed those of European surveillance systems [7].

What Experts Say Is Needed

Epidemiologists and water safety specialists have identified several measures they say would reduce Legionnaires' incidence:

1. Mandatory, routine Legionella testing in high-risk buildings — hospitals, long-term care facilities, hotels, and large residential complexes — rather than relying on process-based WMPs alone [7][4].

2. Updated plumbing codes that account for low-flow fixtures and mandate pipe sizing appropriate to modern usage patterns, reducing water age in building systems [14].

3. Standardized diagnostic testing protocols for hospitalized pneumonia patients, so that cases are identified rather than treated empirically and discharged without a Legionella diagnosis [7].

4. Dedicated funding for state and local public health laboratories to build Legionella environmental testing capacity, enabling investigation of individual cases rather than waiting for clusters [7].

5. Harmonized temperature standards that resolve the conflict between anti-scalding rules and the temperatures required to suppress bacterial growth [14].

Building owners and water utilities have pushed back on several of these proposals. The primary objections center on cost — particularly for routine testing, which requires specialized laboratory analysis — and liability exposure, since testing that reveals Legionella contamination creates a documented record that can be used in subsequent litigation [12]. Some property management groups argue that voluntary WMP adoption, combined with CMS requirements for healthcare facilities, provides adequate protection without the burden of across-the-board mandates.

Insurers have taken a middle position, increasingly requiring WMPs as a condition of coverage while stopping short of endorsing mandatory government testing programs [13].

What Comes Next

The NCDHHS advisory provides guidance but not enforcement. North Carolina's existing Legionnaires' Disease Prevention Act provides a legislative framework, but the 54% case increase in 2025 raises questions about whether the current approach — voluntary compliance for most buildings, with mandatory WMPs for covered facilities — is sufficient.

The warm months ahead will test whether the state's prevention guidance translates into action. Cooling towers, decorative fountains, and building water systems across the state are entering the season when Legionella growth accelerates. Whether building operators flush stagnant lines, maintain adequate water temperatures, and conduct the testing that would catch contamination before it becomes exposure will determine whether the 2025 spike becomes a trend or an outlier.

The data limitations are real. Without systematic testing of pneumonia patients, without public reporting of compliance rates under HB 909, and without demographic breakdowns of the 2025 cases, the full scope of the problem remains obscured. What is clear is that 310 confirmed cases represent, by expert estimates, only a fraction of actual infections — and that the infrastructure, regulatory, and diagnostic gaps that allow Legionella to proliferate in building water systems remain largely unaddressed.