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Appendix B

Descriptions of Selected Waterborne Disease Outbreaks Associated with Drinking Water, Water Not Intended for Drinking, and Water of Unknown Intent

Month

Year

State/Jurisdiction in which outbreak occurred

Etiology

No. of cases (deaths)

Description of outbreak

Bacteria

October

2007

Nevada

Legionella pneumophila serogroup 1

7

During November and December of 2007, two cases of Legionnaire's disease (LD) occurring at the same timeshare condominium were identified through CDC's surveillance system for travel-associated LD; two additional cases were identified in 2008. A subsequent review identified a single case in 2006, and a previous outbreak of legionellosis in 2001 at the same condominium. Seven laboratory-confirmed cases were reported during 2007--2008. The condominium has three towers with individual low- and high-rise potable water systems. Water samples were collected from guest rooms, water heaters, cooling towers, decorative features and recreational facilities, as well as the municipal water source at the water meter, prior to the implementation of extensive remediation efforts. Environmental samples from showerheads and sinks in one of the towers were found to have L. pneumophila that was an identical molecular match to the single clinical isolate available in 2001. Laboratory findings, combined with evidence of sporadic transmission between the first and second outbreak, indicated that long-term colonization of the drinking water system with L. pneumophila had likely occurred at the complex and highlights the importance of travel-associated surveillance systems in linking disease occurrence among geographically-dispersed travelers. No cases were reported at the time-share condominium in 2009 following completion of the second remediation attempt.

July

2008

New York

L. pneumophila serogroup 1

13 (1)

Thirteen residents of an apartment complex for seniors received a diagnosis of Legionnaires' disease. Several water samples from apartment bathroom taps and a hot water cartridge were culture positive for L. pneumophila serogroup 1. The environmental isolates matched patient clinical isolates via pulse-field gel electrophoresis (PFGE). No single event was determined to have led to the outbreak. Potential contributing factors included a previous water main break and subsequent loss in water pressure, disruption and mobilization of an existing biofilm colonized with Legionella, and a hot water heater temperature setting that may have been supportive of Legionella growth.

August

2008

Connecticut

Providencia

55

Fifty-five persons in an apartment complex supplied by water from a community water system became ill with gastrointestinal symptoms. Six of nine stool specimens tested positive for Providencia. None of the stool specimens tested positive for Salmonella, Shigella, Campylobacter, E. coli, parasites, or norovirus. The investigation found a statistically significant association between tap water consumption and illness. Seven well water samples tested negative for Providencia and six of the samples tested positive for E. coli. Raw sewage was visible on the ground after two septic pumps located uphill of the water system wells failed and the septic tank overflowed. Contributing factors in the outbreak included the downhill movement of sewage towards the wells by rainfall and a cracked well casing.

March

2008

Colorado

Salmonella Typhimurium

1,300 (1)

An estimated 1,300 persons became ill when a community drinking water system became contaminated with Salmonella Typhimurium. At the time of the outbreak, a state waiver allowed the distribution of untreated ground water. Twenty persons were hospitalized and one person died. Epidemiologic and environmental findings implicated the community water system. Clinical specimens and tap water tested positive for identical subtypes of S. Typhimurium using pulse-field gel electrophoresis. The likely source of the outbreak was animal contamination of a storage tank that had numerous cracks and entry points. The outbreak response required local, regional, state, and federal emergency assistance over a period of three weeks during which bulk water was distributed by the National Guard while the distribution system was hyperchlorinated. At the time of the outbreak, a new water-treatment plant was under construction, primarily for the purpose of abating naturally high levels of arsenic. Since the outbreak, water is now continuously disinfected at this new plant.

Month

Year

State/Jurisdiction in which outbreak occurred

Etiology

No. of cases (deaths)

Description of outbreak

August

2008

Tennessee

Salmonella serotype I 4,5,12:i:-

5

Five persons were infected with Salmonella serotype I 4,5,12:i:- following consumption of untreated water from a local spring that supplied five homes and a church. The initial case was an infant who was seen by a physician for bloody diarrhea. The regional health department investigated the illness and determined that tap water used to mix powdered formula was the primary risk factor. Tap water collected from the infant's home tested positive for total coliforms and E. coli. The water also tested positive for Salmonella and was a pulse-field gel electrophoresis (PFGE) match to isolates from the infant's stool. A subsequent water sample from the church matched the clinical and tap water samples by PFGE. As a result of the investigation, the Tennessee Department of Environment and Conservation (TDEC) and the regional health department then worked with the affected homes, church and spring owner to provide education and bring the drinking water system into compliance.

Viruses

March

2008

Tennessee

Hepatitis A virus

9

Nine persons tested positive and four persons were hospitalized for infection with hepatitis A virus after spending time at a lakeside residential and vacation community without municipal water or sewer services. Cases were identified among relatives and friends of two resident families. The index case occurred in early March, and the cluster of secondary cases occurred >6 weeks later, in April. The epidemiologic study indicated that person-to-person transmission did not occur. Water samples collected in May from two wells, one supplying the residence of three persons with secondary cases, detected hepatitis A virus by PCR that was the same strain as that in the persons from whom virus specimens were collected. The untreated well water was likely contaminated by a faulty septic system used by the index case-patient, who lived in a mobile home nearby. The public health response included provision of vaccine at three vaccination clinics and provision of postexposure immunoglobulin to >1,500 residents and visitors. Education regarding karst geology and the risks of drinking water from shallow private wells without disinfection was provided to homeowners in the area, and local and state government offices were encouraged to consider extending water utility services to the affected area.

Parasites

April

2008

Puerto Rico

Cyclospora cayetanensis

82

The Puerto Rico Department of Health investigated an outbreak of recurrent diarrhea in a rural community. Of 82 case-patients that were identified, seven were hospitalized. Clinical testing identified Cyclospora cayetanensis in 20 of 26 case-patient stool specimens. An epidemiologic study showed that interruptions in the water service during the past six months, changes in drinking water quality and appearance, and food purchases at a local supermarket were associated with illness; no increased risk was associated with consumption of fruits or vegetables. Interruptions in water service occurred prior to the outbreak, including one interruption during the estimated exposure period when a pumping station was found to be damaged and water was delivered in trucks from another water system and stored in a water tank. Breaks in water supply and changes in water quality were reported by the community during the same time period. Although the source of contamination was not identified, this is the first outbreak of C. cayetanensis in Puerto Rico in which water consumption is considered the probable source of transmission.

July

2007

California

Giardia intestinalis

46

A giardiasis outbreak at a camp that used a spring as its water source resulted in 46 cases of illness. The spring was classified as ground water under the direct influence of surface water and therefore subject to the Environmental Protection Agency's Surface Water Treatment Rule and amendments. An epidemiologic study conducted implicated eating a garden salad and showering as risk factors for illness. Although a slow sand filter and chlorinator had been installed, inadequate time was allowed for formation of a schmutzdecke biological layer on the surface of the filter, which is important for effective treatment performance of slow sand filters. Water samples collected one week after the filter was put into operation showed considerably higher levels of total coliforms and turbidity in filtered water samples than in the spring water samples. Six weeks after operation of the filter a schmutzdecke layer formed and water samples met requirements.

Month

Year

State/Jurisdiction in which outbreak occurred

Etiology

No. of cases (deaths)

Description of outbreak

Chemicals

April

2007

Massachusetts

Sodium hydroxide

145

An estimated 145 persons experienced chemical burns after a sodium hydroxide overfeed altered the pH balance of water passing through a water treatment facility. The pH imbalance occurred overnight when treatment lines were left on a manual setting after routine maintenance. The event activated an onsite alarm system but the facility did not have an automatic notification system for off-site staff. Detection and remediation of the problem at the water treatment facility occurred early the following morning. The emergency response was a coordinated effort that included the local health department and multiple emergency response agencies. Response measures included a Do Not Use order, community education and outreach, consultation with local healthcare facilities and inspection of food and retail establishments prior to re-opening.

Multiple

etiologies

May

2007

Wisconsin

Norovirus genogroup I, Campylobacter, Salmonella

229

Gastrointestinal illness in 229 persons was associated with drinking water exposure at a local restaurant; three stool specimens were positive for enteric pathogens: one for norovirus genogroup 1, one for Campylobacter, and one for Salmonella. Well water tested positive for E. coli and a boiled/bottled water advisory was issued. Subsequent tests found norovirus genogroup I in the water that was identical to the strain in clinical specimens. The restaurant and surrounding residences were located in an area with karst geological features. Tracer dye testing implicated a septic tank as a source of contamination. Underground seepage of sewage and contamination through limestone or fissured rock were thought to contribute to the outbreak.

September

2008

Illinois

Shigella sonnei, Cryptosporidium, Giardia

41

Of 72 persons who gathered for weekend activities that included a dinner cruise on a lake, 41 developed illness attributed to infections with S. sonnei, Giardia, and Cryptosporidium beginning the following day. Environmental inspection revealed conditions and equipment that could have contributed to lake water contaminating the hose used to load potable water onto the boat. Heavy rainfall and flooding the same weekend resulted in the release of a large volume of storm water containing rainwater and highly diluted sewage into the lake. Ice consumption was epidemiologically linked with illness. S. sonnei was isolated from a surface swab of an ice container.

Unidentified

etiology

September

2007

Florida

Unidentified

1,663

An estimated 1,663 cases of gastrointestinal illness occurred in a community water system supplied by surface water and conventionally treated with coagulation, settling, filtration, and disinfection. A boil water advisory was issued two days after fecal coliforms and E. coli were initially found in the water during routine testing. A cross-sectional, random telephone survey of households affected by the boil water advisory found statistically significant associations between water consumption and illness. An independent assessment identified numerous operation and maintenance deficiencies in water disinfection and filtration processes, as well as a segment of outdated pipe that bypassed disinfection steps because it was not known to still be connected to the distribution system. The system was recycling filter backwash water as required by EPA; however, before the outbreak, the backwash water bypassed the recovery basin and ozonation before filtration, thereby adversely affecting filter performance.



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