Global Issues in Water, Sanitation, and Health Workshop Summary (2009) / Chapter Skim
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2 Lessons from Waterborne Disease Outbreaks
2 Lessons from Waterborne Disease Outbreaks
Pages 96-152
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From page 96... ...
Together, they illustrate how an intricate web of factors -- including climate and weather, human demographics, land use, and infrastructure -- contribute to outbreaks of waterborne infectious disease. The chapter begins with an account of the massive cholera epidemic that began in urban areas of Peru in 1991 and swept across South America by Carlos Seas and workshop presenter and Forum member Eduardo Gotuzzo, of Universidad Peruana Cayetano Heredia and Hospital Nacional Cayetano Heredia in Lima, Peru.
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From page 97... ...
THE CHOLERA EPIDEMIC IN PERU AND LATIN AMERICA IN 1991: THE ROLE OF WATER IN THE ORIGIN AND SPREAD OF THE EPIDEMIC Carlos Seas, M.D. Universidad Peruana Cayetano Heredia Eduardo Gotuzzo, M.D., FACP1, Universidad Peruana Cayetano Heredia At Athens a man was seized with cholera. He vomited, and was purged and was in pain, and neither the vomiting nor the purging could be stopped; and his voice failed him, and he could not be moved from his Insitituto de Medicina Tropical Alexander von Humboldt.
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From page 98... ...
During the cholera epidemic in Peru, V cholerae was isolated from many aquatic environments, including not only marine ecosystems, but riverine and lake environments.
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From page 99... ...
cholerae is introduced to humans from its aquatic environment through contamination of food and water sources. The Origins of the Latin American Epidemic The Latin American cholera epidemic was officially declared in Peru during the third week of January 1991, almost simultaneously in three cities along the north coastal area of the country.
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From page 100... ...
Although the epidemic spread to neighboring countries, it never reached the magnitude seen in Peru, which suffered that year from serious economic constraints and reported the lowest level of sanitary coverage and sanitary investment in the region. During 1991, approximately 50 percent of the population in urban cities of Peru received treated municipal water; intermittent supply and clandestine connections were common in many cities of the country (Figure 2-3)
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From page 101... ...
SOURCE: Instituo de Medicina Tropical Alexander von Humboldt, Lima, Peru.
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From page 102... ...
The reduction in typhoid fever incidence was so dramatic that the disease is almost unknown by the generation of physicians trained after 1991, with the subsequent delay in diagnosis and development of complications, an unthinkable situation the decade before 1990. Still, a question remains unanswered: From where did this huge cholera epidemic originate?
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From page 103... ...
. These adult patients attended with severe dehydration and watery diarrhea, clinical presentation that had not been at these health centers the year before the epidemic.
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From page 104... ...
Instituto de Medicina Tropical Alexander von Humboldt; Lima,as WO-10 Rev 2-6 same Peru. Universidad Mayor de San Simón, Cochababmba, Bolivia.
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From page 105... ...
Water temperature affects cholera transmission, as has been observed in the Bay of Bengal, Bangladesh. All these data support the role of ENSO in the interannual variability of endemic cholera.
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From page 106... ...
Contamination of municipal water was the main route of cholera transmission in Trujillo, Peru, during the epidemic in 1991. Drinking unboiled water, introducing contaminated hands into containers used to store drinking water, drinking beverages from street vendors, drinking beverages when contaminated ice had been added, and drinking water outside the home are recognized exposure risk factors for cholera.
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From page 107... ...
, and monitoring the movement and abundance of plankton by satellite seems attractive, but more studies are needed to support the implementation of these methods. Conclusions The cholera epidemic in Latin America was characterized by an explosive beginning with rapid spread in urban areas of Peru and other poor neighboring countries. The available information suggests that environmental factors amplified the existing Vibrio population and induced an epidemic, which was further amplified by contamination of municipal water and food.
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From page 108... ...
, and these spikes in finished water turbidity occurred on multiple days in late March and early April. This was reminiscent of a large waterborne outbreak of Cryptosporidium infections in Carrollton, Georgia, that occurred among customers of a municipal water supply (Hayes et al., 1989)
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From page 109... ...
. FIGURE 2-8 Location of the three rivers that flow through Milwaukee County, Wisconsin, the breakfront protecting the city of Milwaukee harbor, and the northern and southern Milwaukee Water Works water treatment plants and their intake grids.
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From page 110... ...
. There had been several watera ssociated outbreaks in the United States and in the United Kingdom prior to the Milwaukee event, although most were associated with surface water contamina FIGURE 2-9 Maximal turbidity of treated water in the northern and southern water treatment plants of the Milwaukee Water Works from March 1 through April 28, 1993.
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From page 111... ...
Thus, early in our investigation we established that Cryptosporidium was the most likely cause of the outbreak and hypothesized that treated water from the southern water treatment plant was the vehicle for the majority of human infections associated with this outbreak. In addition to the primary task of testing this hypothesis, there were many tasks and questions we sought to address, which included determining • the magnitude and timing of cases associated with the outbreak, • the spectrum of clinical symptoms experienced in a large population of persons infected with Cryptosporidium, • the incubation period of cryptosporidiosis following exposure, • the timing of contamination of Milwaukee water, • the secondary attack rate of cryptosporidiosis among family members not exposed to Milwaukee water, • the frequency of recurrence of the symptoms of cryptosporidiosis after initial recovery, • the presence of Cryptosporidium oocysts in Milwaukee water in water archived during the time of putative exposure of Milwaukee residents, • factors at the MWW southern water treatment plant that allowed Crypto sporidium oocysts to pass through in treated water to infect the public, • mortality associated with the outbreak, • the frequency of asymptomatic infection among exposed Milwaukee resi dents, and • the ultimate source of these Cryptosporidium oocysts: animals or humans.
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From page 112... ...
. Rapid Hypothesis Testing -- Nursing Home Study To rapidly test the hypothesis that the southern water treatment plant was the likely source of the outbreak, we examined rates of diarrhea among geographically fixed populations -- residents of nursing homes -- in different parts of Milwaukee (Mac Kenzie et al., 1994b)
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From page 113... ...
Applying this to the population of the five-county area, and subtracting a background rate of 0.5 percent, we estimated that 403,000 residents had watery diarrhea associated with this outbreak (certainly other people outside the survey area had also become ill, but we could not estimate their numbers; Mac Kenzie et al., 1994b)
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From page 114... ...
We surveyed 74 people who fit this description, of whom 5 percent experienced watery diarrhea; thus, we concluded that the rate of secondary household transmission was quite low (Mac Kenzie et al., 1995b)
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From page 115... ...
Using the membrane filter, we detected 13.2 oocysts per 100 liters of melted ice from March 25 (before the peak in turbidity) , and 6.7 per 100 liters on April 9 (after the boil-water advisory was invoked; Mac Kenzie et al., 1994b)
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From page 116... ...
Following sedimentation, the water was rapidly filtered through sand-filled filtration beds (16 in the north plant and 8 in the south plant) and then stored in a large clear well prior to entry into water distribution pipes (Addiss et al., 1995; Mac Kenzie et al., 1994b)
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From page 117... ...
On April 5, the turbidity of treated water increased to 1.5 NTU. During February through April 1993, the northern plant treated water turbidity did not exceed 0.45 NTU (Mac Kenzie et al., 1994b)
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From page 118... ...
water engineer inspected both Milwaukee water treatment plants and found them to meet existing state and federal water quality standards at the time of the outbreak. However, at the southern plant the water quality data showed a marked increase in turbidity, which reflected poor filtration.
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From page 119... ...
SOURCE: Image courtesy of Kathy Blair. FIGURE 2-15 Milwaukee River emptying into the Lake Michigan harbor following a period of high flow and attendant creation of a plume.
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From page 120... ...
120 GLOBAL ISSUES IN WATER, SANITATION, AND HEALTH FIGURE 2-16 Location of the three rivers that flow through Milwaukee County, Wisconsin, the breakfront protecting the city of Milwaukee harbor and the northern and southern Milwaukee Water Works water treatment plants and their intake grids, and depiction of creation and southerly flow of a plume toward the southern plant and through a gap in the breakfront near the plant's intake grid in Lake Michigan. soccer fields.
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From page 121... ...
From the random digit dialing survey, we determined that the highest attack rates of watery diarrhea occurred in people aged 30 to 39 years (Mac Kenzie et al., 1994b)
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From page 122... ...
Consistent application of stringent water quality standards. At the time of the outbreak, drinking water was regulated either by the EPA or by Transmission from human to human and potentially from human to animal.
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From page 123... ...
The random-digit dialing surveys were very valuable in assessing the scope and progress of this large community outbreak; and nursing home surveillance, as described, was very effective (Mac Kenzie et al., 1994b; Proctor et al., 1998)
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From page 124... ...
Physicians, other clinicians, and public health officials clearly needed to broaden and sustain the index of suspicion for Cryptosporidium infection (Mac Kenzie et al., 1994b)
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From page 125... ...
Cryptosporidium oocysts in untreated water from Lake Michigan that entered the plant were inadequately removed by the coagulation and filtration process at the Milwaukee southern water treatment plant. Water quality standards were inadequate to prevent this outbreak.
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From page 126... ...
The intake grid for raw water entering the southern plant was moved considerably further eastward. These efforts resulted in continuous production by the MWW of high-quality treated water with mean turbidities of 0.01 NTU (Mac Kenzie et al., 1994a)
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From page 127... ...
experienced an outbreak of waterborne disease that killed seven people and caused serious illness in many others. The contamination was ultimately traced to a source that had been identified 22 years earlier as a threat to the drinking water system, but no remedial action was taken to manage the public health risk.
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From page 128... ...
Stan Koebel, the general manager of the Walkerton Public Utilities Commission (PUC) , was responsible for managing the overall operation of the drinking water supply and the electrical power utility.
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From page 129... ...
That afternoon, according to the daily operating sheets, foreman Frank Koebel performed the routine daily checks on pumping flow rates and chlorine usage, and measured the chlorine residual on the water entering the distribution system. He recorded a daily c hlorine residual measurement of 0.75 mg/L for Well 5 treated water on May 13 and again for May 14 and 15.
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From page 130... ...
The May 15 samples taken by the PUC repeated the problems with inadequate sample volumes and discrepancies in the paperwork. Early on the morning of Wednesday, May 17, the lab phoned Stan Koebel to advise him that all of the water main construction project samples taken May 15 were positive for E
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From page 131... ...
The failure by PUC personnel to mention any problems with the Walkerton water system allowed health officials to continue with their misinformed search for a foodborne cause of the outbreak. At that time, Health Unit personnel were not aware that any outbreaks of this disease had occurred in a chlorinated drinking water system.
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From page 132... ...
coli O157:H7 should be interviewed for more details, and he returned that evening to Owen Sound. David Patterson called Stan Koebel to advise him that a local radio station was reporting that Walkerton water should not be consumed.
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From page 133... ...
MacKay was advised that Stan Koebel had been contacted, but that MacKay's concern about drinking water safety was really a matter for the Ministry of Health. This feedback from the MOE was wrong: the MOE was designated as the lead agency for drinking water regulation in Ontario.
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From page 134... ...
However, given Stan Koebel's consistent reassurance about the safety of the Walkerton water system, the Health Unit's caution in attributing the outbreak to the local drinking water at this emerging stage of the outbreak is understandable. After issuing the boil water advisory, Dr.
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From page 135... ...
James Earl apparently believed that the boil water advisory eliminated any urgency concerning the revelation about adverse microbial results for Walkerton's drinking water supply. In the meantime, the Health Unit began to plot an outbreak curve that revealed an apparent peak of disease onset for May 17, suggesting a most likely date of contamination between May 12 and 14.
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From page 136... ...
past, they had often consumed Well 5 water before chlorination because they did not recognize the danger of pathogen contamination.10 Direct Causes of the Walkerton Outbreak The immediate direct cause of failure was that organic loading from manure contamination arising from a nearby farm barnyard overwhelmed the fixed chlorine dose that was used by the Walkerton PUC, leaving no disinfection capacity to inactivate the pathogens entering the distribution system. If the chlorine residual had been monitored as it should have been by the PUC operators, this problem would have been immediately evident, but no valid chlorine residuals were measured during the critical period (around May 12)
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From page 137... ...
Yet the Inquiry found "virtually all of the entries on the 1999 daily operating sheets are false. Fictitious entries in the daily operating sheets continued until the outbreak in May 2000." Inquiry Commissioner O'Connor observed: "One of the purposes of measuring chlorine residual is to determine whether contamination is overwhelming the disinfectant capacity of the chlorine." Accordingly, he found: "The scope of the outbreak would very likely have been substantially reduced if the Walkerton PUC operators had measured chlorine residuals at Well 5 daily, as they should have, during the critical period when contamination was entering the system." At least eight days without valid chlorine residual monitoring passed
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From page 138... ...
The Well 7 option was compromised by Frank Koebel's failure to follow Stan Koebel's instructions to replace a defective chlorinator on Well 7, an action that was not taken until May 19. Once the operators became aware that water with no disinfection had entered the distribution system, the water storage should have been dosed with chlorine solution and the mains flushed.
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From page 139... ...
The Koebel brothers did not intend to harm their fellow citizens through their flawed practices. In fact, they continued to drink the water even as the outbreak was unfolding.12 13There were many potential direct causes for this outbreak, including new water main construction, fire events, main breaks and repairs, contamination of treated water storage, cross connections, flooding, and human sewage or sewage sludge contamination of the wells.
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From page 140... ...
The hydrogeologist who conducted the original assessment of this well wrote in his commissioning report: The results of the bacteriological examination indicate pollution from human or animal sources, however, this was not confirmed by the chemical analyses. The supply should definitely be chlorinated and the bacteria content of the raw and treated water supply should be monitored.
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From page 141... ...
Given the location of the PUC shop in the distribution system downstream of Well 5, combined with the documented poor practices of the PUC operators, it was likely that the May 15 sample labeled Well 7 treated was actually taken at the PUC shop and represented Well 5 water entering the distribution system. This sample, the one that Stan Koebel concealed from health authorities, was heavily contaminated with greater than 200 E
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From page 142... ...
"A case was defined as a person with diarrhea, or bloody diarrhea; or stool specimens presumptive positive for E coli O157 or Campylobacter spp.
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From page 143... ...
One of the distribution system sites, along with cultures from the May 23 raw and treated water samples from Well 5, was analyzed by PCR, another molecular diagnostic technique. This technique is able to amplify DNA from a sample to allow extremely sensitive detection for specific genes that may be present.
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From page 144... ...
with permission from IWA Publishing. These results do not provide absolute confirmation that manure from Farm 2 was responsible for contamination of the Walkerton water supply for a number of reasons.
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From page 145... ...
The water produced by all the wells serving Walkerton was supposed to be chlorinated continuously to achieve a chlorine residual of 0.5 mg/L for 15 minutes of contact time (ODWO)
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From page 146... ...
• Water testing was removed from the provincial laboratory without adding any regulatory requirement for mandatory reporting of adverse results by the private labs to the MOE or the local health units. Preventing Drinking Water Outbreaks: Turning Hindsight into Foresight The challenge in preventing drinking water disasters like Walkerton is to learn from the experience of such disasters.
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From page 147... ...
that "Ultimately, the safety of drinking water is protected by effective management systems and operating practices, run by skilled and well-trained staff." Ontario has committed to implementing substantial improvements in the scope and quality of operator training. Operators can prevent a disaster like Walkerton if they assure the following key elements are established and followed (Hrudey and Walker, 2005)
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From page 148... ...
Yet, the source of waterborne disease in the form of microbial pathogens is an ever present risk because these pathogens are found in human fecal waste and in fecal wastes from livestock, pets or wildlife, making any drinking water source at risk of contamination before or after treatment (Hrudey, 2006b)
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From page 149... ...
R Mac Kenzie, N
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From page 150... ...
1991. Cryptosporidiosis in the Isle of Thanet: an outbreak associated with local drinking water.
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From page 151... ...
2004. Heavy rainfall and waterborne disease outbreaks: the Walkerton example.
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From page 152... ...
2004. Safe drinking water -- lessons from recent outbreaks in affluent nations.
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