Waterborne Disease in US 2025
Waterborne diseases continue to present considerable public health challenges across the United States despite sophisticated water treatment systems and regulatory oversight. These illnesses stem from exposure to contaminated water through various pathways including drinking water systems, recreational water venues, and environmental water sources. The Centers for Disease Control and Prevention maintains comprehensive surveillance systems that track disease outbreaks and estimate the overall burden of waterborne illnesses on American communities.
The spectrum of waterborne pathogens affecting Americans ranges from bacteria like Legionella and nontuberculous mycobacteria that thrive in building plumbing systems to parasites such as Cryptosporidium and Giardia that contaminate drinking water sources. Recent data reveals that biofilm-associated pathogens have emerged as the predominant causes of hospitalizations and deaths from waterborne disease, while enteric pathogens continue to cause substantial numbers of illnesses particularly linked to contaminated groundwater sources. Understanding these disease patterns helps public health officials and water system operators implement targeted prevention strategies.
Key Waterborne Disease Facts in the US 2025
| Waterborne Disease Fact | Statistical Data | Time Period |
|---|---|---|
| Total Annual Waterborne Illnesses | 7.15 million cases | 2014 Estimate |
| Annual Hospitalizations | 118,000 hospitalizations | 2014 Estimate |
| Annual Deaths | 6,630 deaths | 2014 Estimate |
| Direct Healthcare Costs | $3.33 billion | 2014 Estimate |
| Risk of Waterborne Illness | 1 in 44 Americans gets sick annually | 2014 Estimate |
| Deaths Linked to Recreational Water | ~1,290 deaths | 2014 Estimate |
| Deaths Linked to Drinking Water | 3,300 deaths | 2014 Estimate |
| Leading Illness Cause | Acute otitis externa (swimmer’s ear) – 4.67 million cases annually | 2014 Estimate |
| Second Leading Illness | Norovirus infection – 1.33 million cases annually | 2014 Estimate |
| Leading Hospitalization Cause | Nontuberculous mycobacterial infection – 51,400 hospitalizations | 2014 Estimate |
| Leading Death Cause | Nontuberculous mycobacterial infection – 3,800 deaths | 2014 Estimate |
| Drinking Water Outbreaks (2015-2020) | 214 outbreaks reported | 2015-2020 |
| Cases from Drinking Water Outbreaks | 2,140 illnesses, 563 hospitalizations, 88 deaths | 2015-2020 |
| Recreational Water Outbreaks (2015-2019) | 208 outbreaks with 3,646 cases | 2015-2019 |
Data Source: CDC Waterborne Disease and Outbreak Surveillance System; Emerging Infectious Diseases Journal Volume 27, Number 1, January 2021; MMWR Surveillance Summaries Volume 73, Number 1, March 2024
The data demonstrates that waterborne diseases impose substantial health and economic burdens on the United States population. The annual estimate of 7.15 million illnesses represents approximately 1 in 44 Americans falling ill from waterborne pathogens each year. While most cases involve relatively mild infections like swimmer’s ear, the 118,000 annual hospitalizations and 6,630 deaths underscore the serious consequences certain waterborne pathogens can produce. The $3.33 billion in direct healthcare costs reflects only hospitalization and emergency department expenses, not accounting for outpatient care, lost productivity, or long-term health consequences. Notably, biofilm-associated pathogens particularly nontuberculous mycobacteria and Legionella account for disproportionate shares of severe outcomes, causing 44% and 57% of hospitalizations and deaths respectively despite causing fewer total illnesses than enteric pathogens.
The outbreak surveillance data from 2015-2020 reveals 214 drinking water-associated outbreaks causing 2,140 cases of illness, while 2015-2019 saw 208 recreational water outbreaks affecting 3,646 individuals. These outbreak numbers likely underestimate true occurrence since reporting remains voluntary and investigation capabilities vary across jurisdictions. The data clearly identifies Legionella as the predominant drinking water outbreak pathogen, responsible for 86% of outbreaks during the surveillance period, while Cryptosporidium dominated recreational water outbreaks causing 49% of confirmed outbreaks and 84% of outbreak-associated cases. Understanding these patterns enables targeted interventions at water treatment facilities, recreational venues, and healthcare settings where vulnerable populations face elevated risks.
Most Common Waterborne Diseases in the US 2025
| Disease | Estimated Annual Cases | 95% Credible Interval | Percentage of Total |
|---|---|---|---|
| Otitis Externa (Swimmer’s Ear) | 4,670,000 | 2,350,000 – 7,290,000 | 65% |
| Norovirus Infection | 1,330,000 | 5,310 – 5,510,000 | 19% |
| Giardiasis | 415,000 | 140,000 – 816,000 | 6% |
| Cryptosporidiosis | 322,000 | 61,700 – 993,000 | 5% |
| Campylobacteriosis | 171,000 | 13,900 – 586,000 | 2% |
| Other Diseases | 242,000 | Variable | 3% |
| Total Waterborne Illnesses | 7,150,000 | – | 100% |
Data Source: CDC Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States, 2014
Swimmer’s ear or acute otitis externa dominates the waterborne disease landscape with an estimated 4.67 million cases annually, representing nearly two-thirds of all waterborne illnesses in the United States. This external ear canal infection occurs when contaminated water remains in the ear after swimming or bathing, creating conditions favorable for bacterial growth. Despite being the most common waterborne disease, swimmer’s ear generally produces mild to moderate symptoms and responds well to antibiotic ear drops. The substantial case numbers reflect widespread exposure to recreational water and the relative ease of infection transmission rather than disease severity.
Norovirus infection ranks second with approximately 1.33 million waterborne cases each year, accounting for 19% of the total burden. This highly contagious virus spreads readily through contaminated drinking water, particularly from wells and private water systems lacking adequate disinfection. Giardiasis affects 415,000 Americans, cryptosporidiosis causes 322,000 infections, and campylobacteriosis results in 171,000 cases annually through waterborne transmission routes. These parasitic and bacterial infections produce gastrointestinal symptoms ranging from mild diarrhea to severe dehydration requiring hospitalization. The wide credible intervals for these estimates reflect uncertainty in surveillance data and the challenges of attributing infections specifically to waterborne transmission versus other routes like foodborne or person-to-person spread. Collectively, these five diseases account for 97% of all estimated waterborne illnesses, demonstrating the concentrated nature of the disease burden among a relatively small number of pathogens.
Waterborne Disease Hospitalizations in the US 2025
| Disease | Estimated Annual Hospitalizations | 95% Credible Interval | Percentage of Total |
|---|---|---|---|
| Nontuberculous Mycobacterial Infection | 51,400 | 26,800 – 74,100 | 44% |
| Otitis Externa (Swimmer’s Ear) | 23,200 | 13,900 – 33,600 | 20% |
| Pseudomonas Pneumonia | 15,500 | 4,130 – 28,100 | 13% |
| Legionnaires’ Disease | 10,800 | 7,280 – 13,100 | 9% |
| Pseudomonas Septicemia | 5,590 | 722 – 14,000 | 5% |
| Other Diseases | 11,510 | Variable | 9% |
| Total Hospitalizations | 118,000 | – | 100% |
Data Source: CDC Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States, 2014
The hospitalization profile for waterborne diseases differs dramatically from the overall illness pattern, with biofilm-associated pathogens causing disproportionate numbers of severe cases requiring inpatient care. Nontuberculous mycobacterial (NTM) infections lead all waterborne diseases in hospitalizations with an estimated 51,400 cases annually, representing 44% of the total. These slow-growing bacteria colonize premise plumbing systems and building water infrastructure, particularly affecting immunocompromised individuals, those with underlying lung diseases, and elderly populations. NTM infections cause chronic pulmonary disease, skin and soft tissue infections, and disseminated disease in severely immunocompromised patients, often requiring months of multi-drug antibiotic therapy.
Swimmer’s ear hospitalizations reach 23,200 annually despite the generally mild nature of most infections, accounting for 20% of waterborne disease hospitalizations. These hospitalizations typically involve cases with complications like cellulitis spreading beyond the ear canal, malignant otitis externa in diabetic or immunocompromised patients, or severe pain requiring intravenous antibiotics. Pseudomonas pneumonia causes 15,500 hospitalizations (13% of total) while Legionnaires’ disease accounts for 10,800 (9%), both representing serious respiratory infections predominantly affecting vulnerable populations in healthcare facilities and other institutional settings. Pseudomonas septicemia results in 5,590 hospitalizations (5%), representing the most severe manifestation of Pseudomonas infection with bloodstream involvement. The dominance of biofilm-associated pathogens in hospitalization statistics reflects both their ability to cause severe disease and their prevalence in healthcare settings where vulnerable populations congregate. These five conditions account for 90% of all waterborne disease hospitalizations, underscoring the concentrated burden among pathogens thriving in building water systems.
Waterborne Disease Deaths in the US 2025
| Disease | Estimated Annual Deaths | 95% Credible Interval | Percentage of Total |
|---|---|---|---|
| Nontuberculous Mycobacterial Infection | 3,800 | 1,950 – 5,620 | 57% |
| Legionnaires’ Disease | 995 | 655 – 1,310 | 15% |
| Pseudomonas Pneumonia | 730 | 185 – 1,460 | 11% |
| Pseudomonas Septicemia | 695 | 89 – 1,740 | 10% |
| Swimmer’s Ear | 219 | 107 – 367 | 3% |
| Other Diseases | 191 | Variable | 4% |
| Total Deaths | 6,630 | – | 100% |
Data Source: CDC Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States, 2014
Waterborne disease mortality concentrates heavily among biofilm-associated pathogens with nontuberculous mycobacteria causing an estimated 3,800 deaths annually, representing 57% of all waterborne disease deaths in the United States. NTM infections prove particularly deadly because they affect immunocompromised individuals and those with underlying lung diseases who struggle to clear these persistent infections. The organisms’ resistance to standard disinfection procedures and ability to survive in premise plumbing create ongoing exposure risks particularly in healthcare facilities where vulnerable patient populations reside. Treatment requires prolonged multi-drug regimens that may span 12 to 18 months, and many patients experience disease progression despite appropriate therapy.
Legionnaires’ disease accounts for 995 deaths (15% of total), making it the second-leading cause of waterborne disease mortality. This severe pneumonia caused by Legionella pneumophila produces high mortality rates particularly among elderly patients, smokers, and those with chronic lung diseases or weakened immune systems. Pseudomonas causes 1,425 combined deaths through pneumonia (730 deaths, 11%) and septicemia (695 deaths, 10%), reflecting this pathogen’s ability to cause both respiratory and bloodstream infections in hospitalized and immunocompromised patients. Even swimmer’s ear contributes 219 deaths (3%) annually, typically involving malignant otitis externa cases in diabetic patients where infection spreads to skull bones and brain tissue. These five conditions cause 97% of all waterborne disease deaths, demonstrating that while millions contract waterborne illnesses annually, severe outcomes concentrate among specific pathogens predominantly affecting vulnerable populations. The 6,630 total annual deaths from waterborne disease exceed deaths from many better-publicized infectious diseases, highlighting the ongoing public health importance of water safety.
Emergency Department Visits for Waterborne Disease in the US 2025
| Disease | Estimated Annual ED Visits | 95% Credible Interval | Percentage of Total |
|---|---|---|---|
| Otitis Externa (Swimmer’s Ear) | 567,000 | 337,000 – 823,000 | 94% |
| Norovirus Infection | 26,300 | 105 – 106,000 | 4% |
| Nontuberculous Mycobacterial Infection | 5,080 | 2,560 – 7,750 | 1% |
| Legionnaires’ Disease | 667 | 289 – 1,200 | <1% |
| Giardiasis | 567 | 185 – 1,120 | <1% |
| Other Diseases | 1,386 | Variable | <1% |
| Total ED Visits | 601,000 | – | 100% |
Data Source: CDC Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States, 2014
Emergency department utilization for waterborne diseases shows swimmer’s ear overwhelming dominance with approximately 567,000 ED visits annually, accounting for 94% of all waterborne disease emergency care. These visits typically involve patients experiencing severe ear pain, drainage, or fever who seek immediate relief outside regular clinic hours. While most swimmer’s ear cases resolve with antibiotic ear drops prescribed during outpatient visits, ED presentations often reflect severity of symptoms, lack of access to primary care, or occurrence during evenings and weekends when clinics close. The high ED utilization rate for this condition drives substantial healthcare costs despite its generally benign nature.
Norovirus infection generates 26,300 ED visits (4% of total), primarily involving patients with severe dehydration from vomiting and diarrhea requiring intravenous fluid administration. NTM infections account for 5,080 ED visits (1%), Legionnaires’ disease causes 667 visits (less than 1%), and giardiasis results in 567 visits (less than 1%). The relatively low ED utilization for these serious infections compared to their hospitalization and death rates reflects their typically gradual onset allowing patients to seek care through scheduled appointments rather than emergency services. The 601,000 total annual ED visits for waterborne diseases represent significant acute care system burden and contribute substantially to direct healthcare costs. The concentration of over 99% of ED visits among just five diseases enables targeted public health messaging around swimmer’s ear prevention and norovirus outbreak response to reduce unnecessary emergency care utilization.
Direct Healthcare Costs of Waterborne Disease in the US 2025
| Disease | Annual Hospitalization Costs | Annual ED Visit Costs | Total Annual Costs | Percentage of Total |
|---|---|---|---|---|
| Nontuberculous Mycobacterial Infection | $1,520,000,000 | $8,170,000 | $1,530,000,000 | 46% |
| Swimmer’s Ear | $285,000,000 | $280,000,000 | $564,000,000 | 17% |
| Pseudomonas Pneumonia | $452,000,000 | Minimal | $453,000,000 | 14% |
| Legionnaires’ Disease | $401,000,000 | Minimal | $402,000,000 | 12% |
| Pseudomonas Septicemia | $214,000,000 | Minimal | $214,000,000 | 6% |
| Norovirus Infection | Minimal | $30,100,000 | $30,100,000 | 1% |
| Other Diseases | $138,000,000 | $1,880,000 | $140,000,000 | 4% |
| Total Costs | $3,010,000,000 | $320,000,000 | $3,330,000,000 | 100% |
Data Source: CDC Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States, 2014
The economic impact of waterborne diseases reaches $3.33 billion annually in direct healthcare expenditures for hospitalizations and emergency department visits alone, with nontuberculous mycobacterial infections accounting for $1.53 billion (46% of total costs). These infections require prolonged hospitalizations averaging multiple weeks, complex multi-drug antibiotic regimens, extensive diagnostic imaging and laboratory monitoring, and frequent readmissions for disease complications. The $1.52 billion in NTM hospitalization costs dwarfs the $8.17 million in ED costs for this condition, reflecting that NTM patients typically present through scheduled care rather than emergency services. This concentration of costs among a relatively small number of cases demonstrates the severe financial burden biofilm-associated pathogens impose on the healthcare system.
Swimmer’s ear generates $564 million (17%) in combined costs split almost evenly between $285 million in hospitalizations and $280 million in ED visits. This cost distribution reflects the condition’s dual nature causing mostly mild cases treated in emergency departments alongside severe complicated infections requiring hospitalization. Pseudomonas pneumonia costs $453 million (14%), Legionnaires’ disease adds $402 million (12%), and Pseudomonas septicemia contributes $214 million (6%) annually. These three biofilm-associated respiratory and bloodstream infections account for $1.07 billion combined, with costs concentrated in intensive care unit stays, mechanical ventilation, and prolonged antibiotic therapy. Norovirus infection costs total $30.1 million (1%) despite affecting over 1.3 million Americans annually, demonstrating that enteric illness typically produces brief self-limited disease with lower per-case healthcare costs than biofilm-associated infections. Together, just six waterborne diseases account for 95% of direct healthcare costs, enabling focused prevention investments with substantial potential economic returns.
Drinking Water Outbreak Statistics in the US 2015-2020
| Outbreak Characteristic | Number | Percentage |
|---|---|---|
| Total Drinking Water Outbreaks Reported | 214 | 100% |
| Total Cases of Illness | 2,140 | – |
| Total Hospitalizations | 563 | 26% of cases |
| Total Deaths | 88 | 4% of cases |
| Biofilm-Associated Outbreaks | 187 | 87% |
| Enteric Illness Outbreaks | 24 | 11% |
| Legionella Outbreaks | 184 | 86% |
| Outbreaks in Public Water Systems | 172 | 80% |
| Outbreaks in Private/Individual Systems | 17 | 8% |
| Outbreaks with Confirmed Etiology | 212 | 99% |
| States Reporting Outbreaks | 28 | – |
Data Source: CDC MMWR Surveillance Summaries Volume 73, Number 1, March 2024
From 2015 through 2020, public health officials across 28 states reported 214 drinking water-associated outbreaks causing 2,140 illnesses, 563 hospitalizations (26% hospitalization rate), and 88 deaths (4% case-fatality rate). The surveillance data reveals biofilm-associated pathogens dominated the outbreak landscape with 187 outbreaks (87% of total) compared to just 24 enteric illness outbreaks (11%). This distribution contrasts sharply with the overall burden estimates showing enteric pathogens causing most illnesses but biofilm-associated organisms producing most severe outcomes. Legionella alone caused 184 outbreaks (86% of all drinking water outbreaks), demonstrating this pathogen’s overwhelming importance in drinking water surveillance.
Public water systems including community and noncommunity systems accounted for 172 outbreaks (80%), while private or individual water systems caused 17 outbreaks (8%). However, individual/private systems produced 944 cases (44% of all outbreak-associated illnesses) despite representing only 8% of outbreaks, indicating these unregulated systems cause larger outbreaks on average than public systems. Nearly all outbreaks 212 of 214 (99%) had confirmed etiologies, reflecting improved laboratory diagnostic capabilities and investigation protocols. The 563 hospitalizations represent a 26% hospitalization rate substantially higher than typical infectious disease outbreak rates, while the 88 deaths yield a 4% case-fatality rate underscoring the severity of drinking water-associated illnesses particularly those caused by Legionella. These outbreak statistics likely underestimate true occurrence since reporting remains voluntary and not all outbreaks receive investigation, but they provide critical insights into drinking water safety challenges requiring ongoing attention.
Legionella Outbreaks in the US 2015-2020
| Legionella Outbreak Data | Number/Value | Details |
|---|---|---|
| Total Legionella Outbreaks | 184 | 2015-2020 period |
| Outbreaks by Year – 2015 | 14 | Lowest year |
| Outbreaks by Year – 2016 | 31 | – |
| Outbreaks by Year – 2017 | 30 | – |
| Outbreaks by Year – 2018 | 34 | – |
| Outbreaks by Year – 2019 | 33 | – |
| Outbreaks by Year – 2020 | 18 | Pandemic impact |
| Total Cases | 786 | 37% of all drinking water cases |
| Total Hospitalizations | 544 | 97% of all drinking water hospitalizations |
| Total Deaths | 86 | 98% of all drinking water deaths |
| Healthcare Setting Outbreaks | 111 | Hospitals, long-term care, assisted living |
| Hotel/Lodging Outbreaks | 35 | Hotels, motels, lodges, inns |
| Public System Association | 160 | 92% of Legionella outbreaks |
Data Source: CDC MMWR Surveillance Summaries Volume 73, Number 1, March 2024
Legionella emerged as the dominant drinking water outbreak pathogen during the 2015-2020 surveillance period, causing 184 outbreaks representing 86% of all reported drinking water outbreaks in the United States. The annual outbreak count demonstrated general upward trends from 14 outbreaks in 2015 climbing to peaks of 34 in 2018 and 33 in 2019, before declining to 18 in 2020 likely reflecting COVID-19 pandemic impacts on building water systems and outbreak investigation capacity. This increasing trend over most of the surveillance period indicates growing recognition of Legionella as a waterborne pathogen, improved diagnostic testing and outbreak detection, or actual increases in Legionella presence within building water systems from aging infrastructure and complex plumbing.
Despite causing only 786 cases (37% of all drinking water outbreak illnesses), Legionella outbreaks resulted in 544 hospitalizations (97% of total) and 86 deaths (98% of total) during this period. These statistics demonstrate Legionnaires’ disease severity with nearly 70% of cases requiring hospitalization and approximately 11% proving fatal. Healthcare facilities accounted for 111 Legionella outbreaks including hospitals, long-term care facilities, and assisted living centers where vulnerable populations face heightened risk. Hotels, motels, lodges and inns experienced 35 outbreaks, representing settings where transient populations encounter contaminated building water systems. Public water systems were implicated in 160 Legionella outbreaks (92%) including 666 cases, 462 hospitalizations (97% of public system hospitalizations), and 68 deaths (97% of public system deaths). The concentration of Legionella outbreaks in specific settings enables targeted prevention through water management programs, but ongoing increases highlight the need for sustained attention to building water system safety particularly in facilities serving elderly and immunocompromised populations.
Enteric Pathogen Outbreaks in the US 2015-2020
| Enteric Outbreak Data | Number | Percentage/Details |
|---|---|---|
| Total Enteric Illness Outbreaks | 24 | 11% of drinking water outbreaks |
| Total Cases from Enteric Outbreaks | 1,299 | 61% of all outbreak cases |
| Total Hospitalizations | 10 | 2% of cases |
| Total Deaths | 0 | No fatalities |
| Norovirus Outbreaks | 7 | 3% of all outbreaks |
| Shigella Outbreaks | 4 | 2% of all outbreaks |
| Campylobacter Outbreaks | 2 | 1% of all outbreaks |
| Cryptosporidium Outbreaks | 2 | 1% of all outbreaks |
| Giardia Outbreaks | 3 | 1% of all outbreaks |
| Multiple Etiology Outbreaks | 5 | 2% of all outbreaks |
| Largest Single Outbreak Cases | 693 | Norovirus/E. coli at amusement park |
| Well-Associated Outbreaks | 13 | 93% when water source known |
| Individual/Private System Cases | 944 | 73% of enteric outbreak cases |
Data Source: CDC MMWR Surveillance Summaries Volume 73, Number 1, March 2024
Enteric illness outbreaks represented just 24 outbreaks (11% of total drinking water outbreaks) during the 2015-2020 period but generated 1,299 cases (61% of all outbreak-associated illnesses), demonstrating these pathogens cause larger outbreaks on average than biofilm-associated organisms. Norovirus led enteric pathogens with 7 outbreaks, followed by Shigella with 4 outbreaks, Giardia with 3, and Campylobacter and Cryptosporidium each causing 2 outbreaks. An additional 5 outbreaks involved multiple enteric pathogens simultaneously, highlighting the common occurrence of co-contamination particularly in groundwater sources. These enteric outbreaks resulted in only 10 hospitalizations (less than 1% of cases) and no deaths, contrasting dramatically with Legionella’s 70% hospitalization rate and substantial mortality.
The most striking finding involved one massive outbreak at an amusement park where 693 individuals (32% of all enteric outbreak cases) contracted illness from water contaminated with norovirus and enteropathogenic E. coli supplied by an improperly constructed well with inadequate disinfection. This single event demonstrates how groundwater contamination combined with treatment failures can produce extensive outbreaks rapidly. When water source information was reported, wells were identified in 13 of 14 enteric illness outbreaks (93%) regardless of water system type, underscoring groundwater vulnerability to fecal contamination. Individual or private water systems accounted for 944 cases (73% of all enteric outbreak illnesses) despite representing only 8% of total outbreaks, highlighting unregulated private wells’ substantial contribution to enteric disease burden. The settings varied widely including mobile home parks, lodging facilities, farms, camps and private residences. No disinfection was reported in nearly 75% of enteric outbreaks when treatment information was known, emphasizing proper well construction, location, and treatment as critical prevention strategies.
Recreational Water Outbreak Statistics in the US 2015-2019
| Recreational Water Outbreak Data | Number | Percentage |
|---|---|---|
| Total Treated Recreational Water Outbreaks | 208 | 100% |
| Total Cases | 3,646 | – |
| Total Hospitalizations | 286 | 8% of cases |
| Total Deaths | 13 | 0.4% of cases |
| States Reporting | 36 plus DC | – |
| Public Venue Outbreaks | 199 | 96% |
| Confirmed Infectious Etiology | 155 | 75% |
| Cryptosporidium Outbreaks | 76 | 49% of confirmed |
| Cryptosporidium Cases | 2,492 | 84% of confirmed cases |
| Legionella Outbreaks | 65 | 42% of confirmed |
| Hotel-Associated Outbreaks | 71 | 34% |
| June-August Start | 107 | 51% |
Data Source: CDC MMWR Morbidity and Mortality Weekly Report Volume 70, Number 20, May 2021
Public health officials from 36 states and the District of Columbia reported 208 outbreaks associated with treated recreational water during 2015-2019, resulting in 3,646 cases, 286 hospitalizations (8% of cases), and 13 deaths (0.4% of cases). Nearly all outbreaks 199 or 96% occurred in public nonbackyard pools, hot tubs, or water playgrounds, demonstrating that properly designed and operated facilities still experience disease transmission. Among the 155 outbreaks with confirmed infectious etiology (75% of total), two pathogens dominated: Cryptosporidium caused 76 outbreaks (49% of confirmed outbreaks) with 2,492 cases (84% of confirmed outbreak cases), while Legionella caused 65 outbreaks (42% of confirmed) primarily associated with hot tubs.
Cryptosporidium’s prominence in recreational water outbreaks reflects this parasite’s extreme chlorine tolerance, surviving more than 7 days in properly chlorinated water at standard 1 ppm free chlorine concentrations. This resistance enables Cryptosporidium to cause large outbreaks affecting dozens to hundreds of swimmers even when pools maintain recommended disinfectant levels. Hotels, motels, lodges, inns or resorts accounted for 71 outbreaks (34% of total), representing settings where transient guests use aquatic facilities. Over half the outbreaks (107 or 51%) started during June through August, coinciding with peak swimming season and increased aquatic venue use. The 286 hospitalizations primarily involved Cryptosporidium cases producing severe dehydration and Legionella infections causing pneumonia. The 13 deaths all resulted from Legionella-associated outbreaks in hot tubs, none from Cryptosporidium despite far greater case numbers.
Disclaimer: The data research report we present here is based on information found from various sources. We are not liable for any financial loss, errors, or damages of any kind that may result from the use of the information herein. We acknowledge that though we try to report accurately, we cannot verify the absolute facts of everything that has been represented.
