Epilogue of the Origin of Cholera in Haiti
By Ralph R. Frerichs, Professor Emeritus of Epidemiology, UCLA , July 20, 2011.
Near my home in dry Southern California, fires every few years scorch the hillsides, sometimes burning buildings, and even causing deaths. Once the immediate carnage is over, the fire inspectors arrive and do their detective work, seeking to determine if downed power lines, lightning or human activity started the fires. Most everyone recognizes that such detective work is important, and few would trivialize this etiologic pursuit.
In many ways the cholera situation in Haiti is similar, except the devastating agent is a microbe rather than a flame. Public health officials must first deal with the raging epidemic, containing the spread and bringing it under control. But then the focus should again be on the origin, to find out why the outbreak or epidemic look place, thereby gaining insights to prevent future occurrences.
John Snow and Cholera in Haiti
So how would epidemiologist John Snow have reacted to the cholera outbreak in Haiti? Would he have reflected on his experiences with the two great London studies in 1854, namely the Grand Experiment and the Broad Street Pump Outbreak? Back then, it is not unlikely that critics and colleagues warned him to avoid negative writing about the powerful water companies, which potentially could hurt his medical and research career. Or others might have suggested Snow not incriminate popular neighborhood pumps, since they were a convenient source of local water and frequently a symbol of neighborhood pride. Why not just go out and tend the sick and dying, and leave water companies and pumps alone, since isn't addressing the devastating medical and social impact of cholera disease more important than detective work on some etiological event in the past? Finally, still others might have conceded that Snow presented interesting epidemiological associations, but felt that in reality he did not isolate the causative organism (this was left to Robert Koch in 1884), and thus was not able to fully prove his theories.
Such critics continued their debates long after Snow's death in 1858, and certainly well into London's next cholera epidemic of 1866 (1). But then gradually reality took hold and many came around, recognizing that Snow was a friend, not foe, and that his studies of etiology were essential for understanding an outbreak or epidemic, and establishing effective intervention and prevention policies. But that, as we say, is history, and then is then and now is now. Or is it?
Since the major articles and reports have now been published on cholera in Haiti, I would like to summarize what has been written and provide an epilogue on the "origin" aspect of the epidemic. Others have done the same, so mine will be just one more epidemiologic opinion to assist the thoughtful reader.
My approach to presenting what took place will use the epidemiologic triad of agent, host and environment, interacting to create index (or first) cases, which in turn sparks an epidemic as one patient passes the disease on to another. Once the epidemic is underway, there are many additional factors that contribute to the further spread of the disease, but they will not be part of this "origin" Epilogue.
The cholera epidemic in Haiti began on Thursday, October 14, 2010 in the small village of Meille (also spelled Méyè), south of the city of Mirebalais and just west of MINUSTAH, the United Nations camp housing peacekeeping troops from Nepal. I will first focus on what happened before the index cases occurred, and then address the early stages of the epidemic, describing how the first cases came about. Since the story is time-dependent, I will be including calendars to highlight when various events took place in relationship to the index cases.
Cholera in Kathmandu, Nepal
Cholera has been present in Nepal for quite some while. In 2008-2009, cholera in Nepal was documented as V. cholerae serotype O1, serogroup Ogawa in the Japanese Journal of Infectious Diseases (2). Most recently, a cholera organism from 2009 in Nepal was found by a UN panel to be "a perfect match" with cholera organism found in Haiti (3). So there is a historical connection between these two countries (at least to 2009) based on the molecular footprint of the microbe. Note: there was an error in the UN report. The sentence regarding 2009 should have read, "A careful analysis of the MLVA results and the ctxB gene indicated that the strains isolated in Haiti and Nepal during 2010 were a perfect match." (3a)
In September, 2010, shortly before Nepalese troops were assembled to leave Kathmandu for Haiti as United Nations peacekeepers, cholera was again at epidemic levels in Nepal (4). Vibrio cholerae specimens from this outbreak are being stored at the National Public Health Laboratory (NPHL) in the Teku region of Kathmandu, although this has not been confirmed or denied by the Nepalese government. Yet, according to Sameer Dixit, PhD, Country Director for the Centre for Molecular Dynamics in Nepal (CMDN), "... the samples and expertise required to establish such a link (i.e., between Nepal and Haiti) (or not) exist in Nepal itself (5)."
Dixit continues, "The governmental laboratory (NPHL) has bacterial strains from the outbreak areas in Nepal and the CMDN affiliated Molecular Laboratory has the DNA. Molecular biotechnology could have been used to determine whether the Nepalese peacekeeping contingent in Haiti deserved the blame heaped upon it, through evidence-based findings, but it has not been (5)."
Of course, the Government of Nepal is placed in an unfavorable light by not offering to assist the Government of Haiti or the United Nations in the molecular characterizations of the 2010 strain of V. cholerae. This lack of action does not prove that the origin of the Haiti cholera was not Nepal, but rather raises suspicion that the Government of Nepal may have something to hide.
Fortunately, two specimens of V. cholerae serotype O1, serogroup Ogawa from 2010 where gathered by scientists at the International Vaccine Institute in Seoul, Korea. According to the UN panel report (3), the 2010 specimens are now being genetically sequenced, and could add further insight as to the Nepal-Haiti microbial link.
Cholera in Haiti
Most of the characterizations of Vibrio cholerae from the Haiti epidemic were done with specimens collected in Haiti. Laboratory investigators attempted to use their findings in Haiti to look backwards and determine where the microbe likely originated.
The first report came from the Haitian Ministry of Public Health and Population (MSPP) and the United States CDC. In less than a week after the epidemic started, the investigators used rapid tests on eight specimens collected on October 19-20, 2010 to identify the organism as V. cholerae 01.Thereafter on October 22nd, the National Public Health Laboratory in Haiti reported their detailed analysis of three of the eight specimens, namely that the organism was V. cholerae serogroup O1, serotype Ogawa (6). Finally, CDC did a detailed analysis of 14 isolates associated with the Haiti outbreak, and reported that they were were indistinguishable by all laboratory methods, revealing in a very long name that the outbreak strain was V. cholerae serogroup O1, serotype Ogawa, biotype El Tor, and PulseNet PFGE pattern combination KZGN11.0092/KZGS12.0088 (6).
Following their laboratory work, the CDC investigators concluded that, "...as of November 13, data indicated that a single strain caused illness among the 14 persons from Artibonite Department." They went on to state, "if these isolates are representative of those currently circulating in Haiti, the findings suggest that V. cholerae was likely introduced into Haiti in one event." Finally, they aimed vaguely at Nepal (being in South Asia) by stating, "V. cholerae strains that are indistinguishable from the outbreak strain by all methods used have previously been found in countries in South Asia (a region that includes Nepal) and elsewhere."(6)
The next analysis was done by Chen-Shan Chin, PhD et al, who used a third-generation, single-molecule, real-time DNA sequencing method to determine the genome sequences of two Haitian V. cholerae isolates and three additional V. cholerae clinical isolates from other regions of the world. With these specimens, they felt that they could to determine the probable origin of the cholera outbreak strain in Haiti (7). Very little detail was given on when and where the specimens were collected, other than Haiti. The authors stated, "samples of spontaneously passed stool from two patients who had received a clinical diagnosis of cholera were cultured." They compared their findings with three other specimens, obtained from clinical isolates from a 1991 outbreak in Peru, a 2008 outbreak in Bangladesh, and a 1971 outbreak, also in Bangladesh. Their conclusion was that, "the V. cholerae strain responsible for the expanding cholera epidemic in Haiti is nearly identical to so-called variant seventh-pandemic El Tor O1 strains that are predominant in South Asia, including Bangladesh (7)."
Finally, Chin et al rejected the "climate causal hypothesis" when they wrote, "our data distinguish the Haitian strains from those circulating in Latin America and the U.S. Gulf Coast and thus do not support the hypothesis that the Haitian strain arose from the local aquatic environment. It is therefore unlikely that climatic events led to the Haitian epidemic (7)."
Ali and colleagues presented a third analysis of V. cholerae in Haiti derived from 16 patients with severe diarrhea gathered at St. Nicholas Hospital, St. Marc, Artibonite Department (most likely source, the authors were unclear) during the first three weeks of the Haiti cholera epidemic (8). They used a technique termed, "variable-number tandem-repeat typing" of 187 isolates and found minimal diversity, consistent with a point source for the epidemic, similar to what others had reported.
Ali et al also offered some support in their conclusions for the human origin hypothesis, but did so without mentioning the UN peacekeepers from Nepal. They wrote, "...our findings are consistent with those of others studies implicating southern Asia as the source for these strains on the basis of deletion/insertion data for the superintegron and the sulfamethoxazole/trimethoprim resistance integron island, and from analysis of single nucleotide polymorphisms, including those in the cholera toxin gene identified in the complete sequence of the strain from Haiti." They also appear to refute the climatic hypothesis when they wrote that their findings..."would support the hypothesis that the epidemic in Haiti was caused by 1 clone that had little time to undergo diversification of STs (sequence types) expected of strains persistent in an environmental reservoir for extended periods (8)."
Finally, the UN panel in their section on laboratory investigations wrote: "several independent researchers studying genetic material from the bacteria responsible for the outbreak of cholera in Haiti graciously provided their results to us. They used a variety of molecular analysis techniques to examine multiple samples of the bacteria. Their results uniformly indicate that: 1) the outbreak strains in Haiti are genetically identical, indicating a single source for the Haiti outbreak; and, 2) the bacteria is very similar, but not identical, to the South Asian strains of cholera currently circulating in Asia, confirming that the Haitian cholera bacteria did not originate from the native environs of Haiti (3)."
Thus the UN panel appears to reinforce the opinions of the other groups who analyzed V. cholerae from Haiti in support of the human causal hypothesis. By rejecting the climate causal hypothesis, the UN panel gave no support for the theory that the cholera organism isolated in Haiti arose from the estuary waters of Haiti, dormant until a storm or earthquake stimulated the epidemic. Yet they stopped short of stating that the 2010 organism came from Nepal, although they did mention there there was a perfect match with a 2009 specimen obtained from Nepal.
So now we know about the agent. if Vibrio cholerae did originate in South Asia and likely in Nepal, how did the cholera agent in Nepal get to Haiti? To answer this question, we need to know about the host.
Travel of Cholera from Nepal to Haiti
Since 2004, the United Nations has provided peacekeeping troops to Haiti. The UN peacekeeping troops were part of the United Nations Stabilization Mission In Haiti, although most in Haiti referred to them by their French acronym, MINUSTAH (Mission des Nations Unies pour la stabilisation en Haïti). In January 2010, Haiti experienced a large earthquake that caused havoc in much of the country. More UN peacekeeping troops were requested, including about 1,000 troops from Nepal, coming for six month rotations.
The Nepalese peacekeeping troops that supposedly brought cholera to Haiti were assembled in Kathmandu for three months of training starting in July, 2010. During their time in the Nepal capital, cholera was at epidemic levels (4). According to the UN panel report, a medical examination was completed before they departed Kathmandu (3). If the clinical examination was negative, it was local policy to not collect and test stool specimens. The lack of testing was reiterated by the Nepalese Army's chief medical officer (9), who also stated that none of the troops exhibited symptoms of cholera. As a result, no follow-up stool tests were done.
If cholera symptoms had appeared, the patient would typically have been infected 2 hours to five days earlier; that is the incubation period from initial infection to first showing of signs and symptoms is usually from 2 hours to five days. According to the World Health Organization, about 75% of people infected with V. cholerae do not develop any symptoms (i.e., are asymptomatic), although the bacteria are present in their feces for 7–14 days after infection and are shed back into the environment, potentially infecting other people.
It is near certain that some of the Nepalese troops being sent to Haiti were infected with cholera, either at the time of their medical examination or during the 10 days of home-leave that followed, and then carried the microbe to Haiti to be circulated via contaminated feces.
The first troops left Nepal in October 2010 and arrived at the Mirebalais MINUSTAH camp in the Centre Department of Haiti on October 9, 2010 (10), where they became UN peacekeepers, also known as the "blue helmets." Another group from Nepal arrived on October 12th (10).
What remains unclear is how many in this initial wave of replacement Nepalese troops went to the main MINUSTAH camp near Mirebalais, versus two other camps at Hinche and at Terre Rouge (3).
Finally, according to Piarroux et al, a third group of Nepalese replacement troops arrived on October 16th (10); the UN Panel report differs slightly, stating the Nepalese troops arrived between October 8 and 24th (3). It must be noted, however, that French epidemiologist Piarroux and Haitian colleagues conducted their field investigation less than a month after the index cases had occurred on October 14th (10). Conversely, the UN Panel, comprised of four international cholera experts, were assembled in December, 2010 and went to Haiti in February 13-20, 2011, or four months following the onset of the epidemic (3). Hence the minor date disparities may have been due to memory issues and/or lack of available deployment records.
In summary, the first Nepalese replacement troops were in their MINUSTAH camps on October 9th or 12th, days prior to the index cases in Meille, with some harboring Vibrio cholera serotype O1, serogroup Ogawa, showing either no symptoms or having diarrhea, which in turn was disposed in camp latrines.
The UN Panel in their report wrote that they reviewed clinic data at the Mirebalais MINUSTAH camp and found no cases of severe diarrhea and dehydration during this initial period (3). They did not mention reviewing the medical records of troops assigned to either the Hinche or Terra Rouge MINUSTAH camps. Furthermore, their investigation into the initial disease patterns that occurred in the MINUSTAH camp at Mirebalais prior to October 14 was following a trail that was already four months old by the time they arrived in Haiti, and perhaps misleading, given the reluctance of the Nepalese UN peacekeepers to cooperate and possibly incriminate themselves. Finally, as will be presented next, sewage with fecal matter from the Hinche and Terra Rouge MINUSTAH camps was brought twice weekly to an open septic pit at the Mirebalais camp, where the fluids, mixed with those of the Mirebalais camp, seeped into the Meye Tributary of the Artibonite River, providing another potential source of V. cholerae to infect the local people.
Now that the agent and host have come together, what about the environment where transmission of the disease agent to the susceptible population took place?
Relationship of Infected Hosts, River, and Susceptible Haitians
The MINUSTAH camp is located south of Mirebalais, a city in the Centre Department of Haiti on the banks of the Artibonite River. Two branches of the Meye Tributary System (i.e., a group of small rivers or brooks) flow past the MINUSTAH camp, and then north to empty into the Artibonite River. The small village of Meille, where the first cases appeared, lies to the east of the MINUSTAH camp. According to the UN Panel report, the river flow takes about 2-8 hours to travel north from Meille to the Artibonite River (3).
On October 27, 2010, Associate Press report Jonathan Katz visited the Mirebalais MINUSTAH camp and wrote: "A buried septic tank inside the fence was overflowing and the stench of excrement wafted in the air. Broken pipes jutting out from the back spewed liquid. One, positioned directly behind latrines, poured out a reeking black flow from frayed plastic pipe which dribbled down to the river where people were bathing (11)."
Katz went on to write of the septic tanks on the MINUSTAH base, "Then tanker trucks from the contractor ... arrived to drain the septic tank and dump their contents across the street in the waste pits [later termed "open septic pit" in the UN panel report (3)]. As the septic tank drained, the flows behind the base stopped (11)."
As an aside, Jonathan Katz in April 2011 received the 2010 Medill Medal for Courage in Journalism from Northwestern University's Medill School of Journalism, one of the world's most prominent graduate journalism programs. As the University stated, "Katz reported that horrible conditions at a United Nations camp led to a deadly cholera outbreak throughout the country. The U.N. denied the reports, but after Katz obtained a report from a French scientist [i.e., Piarroux, (12)) that confirmed the origins of the cholera outbreak, the U.N. stopped its denials and appointed an independent panel to examine the issue."
Also commenting about the broken pipes coming from the camp was Piarroux et al, who wrote: "The Haitian epidemiologists (initial investigation, starting Oct. 19th) observed sanitary deficiencies, including a pipe discharging sewage from the camp into the river. Villagers used water from this stream for cooking and drinking (10)."
These broken pipes, flowing into the Meye Tributary System, were likely part of the environment that allowed the cholera agent to move with sewage from the infected Nepalese hosts (i.e., troops) to the susceptible Haitian population who had contact with the river.
Three and a half months later in February 13-20, 2011 during their in-country time, the UN Panel wrote: "There is one main area at the Mirebalais MINUSTAH camp that houses toilet and showering facilities... Black water waste (containing human feces) flows into six 2,500-Liter fiberglass tanks. There are additional soak pits and one concrete tank for black water storage at a separate containment area near the medical facilities. The construction of the water pipes in the main toilet/showering area is haphazard, with significant potential for cross-contamination through leakage from broken pipes and poor pipe connections, especially from pipes that run over an open drainage ditch that runs throughout the camp and flows directly into the Meye Tributary (3)." Note, this observation by the UN panel occurred four months after the index cases were infected, indicating the slow pace of repairs and improvements by the Nepalese "Blue Helmet" troops at the Mirebalais MINUSTAH camp.
As shown in a photo that was taken on February 19, 2011 and included in the UN Panel report, there is much human activity along the banks of the Meye Tributary in the Meille area. As the report stated, the human activity included, ..." women washing, people bathing, people collecting water for drinking, and children playing (3)."
The UN Panel went on to write of their February 2011 visit: "The black water tanks in the main area and medical area of the camp are emptied on demand by a contracting company approved by MINUSTAH headquarters in Port-au-Prince. MINUSTAH staff reported that the contractor empties the tanks twice per week when called. The contracting company dispatches a truck from Port-au-Prince to collect the waste using a pump. The waste is then transported across the street and up a residential dirt road to a location at the top of the hill, where it is deposited in an open septic pit (photo below). ... There is no fence around the site, and children were observed playing and animals roaming in the area around the pit. ... The southeast branch of Meye Tributary System is located a short walk down the hill from the pit (3)."
This poorly constructed and maintained septic pit likely served as a caldron for the concentration of Vibrio cholerae microbes transported from the camp containing the feces of infected (either symptomatic or asymptomatic) Nepalese peacekeeping troops. The index cases in Meille on October 14, 2010 could have been caused by V. cholerae in the sewage flow from the broken pipes or in the twice-weekly deposit of sewage in the leaking open septic pit, or both.
The UN Panel goes on to state, "Black water waste for the two other MINUSTAH facilities – Hinche and Terre Rouge – is also trucked to and deposited in this pit (3)." Thus the (open septic) pit received fecal matter from the Mirebalais MINUSTAH camp, where the UN Panel wrote they had reviewed past medical records (and found them to be negative), and from Hinche and Terre Rouge MINUSTAH camps where there was no mention of such a review.
The plausible agent has now been identified, as has the probable host, along with the likely environment where the disease was transmitted. What follows is how the index cases arose, leading to the wider cholera epidemic that is still underway in Haiti.
In an outbreak investigation, the first disease case other than the initial source case is termed the "index case" or "primary case." In the Haiti, the source cases supposedly are the cholera-infected Nepalese peacekeeping troops who pass the organism in their feces, which then becomes sewage. The sewage in turn contaminates river water, which is then consumed by susceptible Haitians. The first cholera patients among the susceptible Haitians are the index cases. Thereafter following an incubation period of 12-24 hours, these index or primary cases become communicable and pass an infectious dose of V. cholerae in contaminated feces, food or water to secondary Haitian cases.
The disease detective, in trying to find the origin of the epidemic, has to separate the primary from the secondary cases, and then work backward to identify the initial source of the infection. This may not be an easy task, especially with a disease such as cholera since the primary and secondary cases are often hard to distinguish. For example, assume that the open septic pit with V. cholerae-contaminated feces from the Nepalese troops is the mechanisms that links the Nepalese source cases with the Haitian index cases. The septic pit may remain contaminated for quite some while, generating many index cases. In the mean time, the index (or primary) cases are also transmitting the disease via contaminated feces, food or water, resulting in a mixture of primary and secondary cases. At this point, unless the epidemiologist can find the index cases, the source becomes hard to identify. This is why outbreak investigations must be conducted in a timely manner, not waiting until memories fade, records are lost, and environments are changed.
While much has been written about the Haiti cholera epidemic, only one publication has focused on the index cases, and how they were used to identify the likely source (10). When physician epidemiologist Renaud Piarroux was asked in October 2010 by the French and Haitian governments to come to Haiti to investigate the recent cholera outbreak, he willingly step forward. Along with Haitian medical and public health colleagues, Piarroux conducted a field investigation during November 7-27, 2010, with the intent, "...to clarify the source of the epidemic and its unusual dynamic (10)."
In their article, Piarroux et al described gathering clinical and epidemiological data to create a database. These data were then used for a more sophisticated space and time analysis. With this analysis, they highlighted five groups or clusters of cases in Haiti and described the national wave-like expansion of the epidemic within broad geographic groups in October and November, 2010. The first cluster or wave of cases occurred near Mirebalais between October 15 and 19. The second cluster or wave occurred along the Artibonite River between October 20 and 28. The third, fourth and fifth clusters or waves were evident during November in additional regions of the country (10).
For this Epilogue, I am focusing on the origin of the Haiti epidemic, and thus will present the data from the first wave of the Piarroux analysis. As seen in the figure at left [modified from (10)], two events occurred prior to the occurrence of the index cholera cases. The first event of 2010 was the cholera outbreak in Kathmandu, Nepal, described on September 23rd in a news article (4). The second event was the arrival of the incoming Nepalese peacekeeping troops at the MINUSTAH camp in Meille which occurred on October 9th. Another group of Nepalese troops arrived on October 12th (not shown). The index cases of cholera were observed in the village of Meille on October 14th, five days after the arrival of the first group of Nepalese troops and two days after the arrival of the second group of troops.
Piarroux et al wrote of identifying these index cases, with the assistance of both Cuban doctors and Haitian counterparts: "in October 18, the Cuban medical brigades reported an increase of acute watery diarrhea (61 cases treated in Mirebalais during the preceding week) to MSPP (Haitian Ministry of Public Health and Population). On October 18, the situation worsened, with 28 new admissions and 2 deaths. MSPP immediately sent a Haitian investigation team (10)."
Finding the Index Cases in Haiti
It was this Haitian Investigation team that discovered the index cases, and in their interviews found that the Haitian epidemic began on October 14th. Piarroux et al went on to write: "The first hospitalized patients were members of a family living in Meille (also spelled Méyè), a small village 2 km south of Mirebalais. On October 19th, the investigators identified 10 other cases in the 16 houses near the index family’s house. Five of the 6 samples collected in Meille from these outpatients, who became sick during October 14–19, yielded V. cholerae O1, serotype Ogawa, biotype El Tor (10)." The epidemiologic confirmation, based on laboratory findings and signs and symptoms, occurred on October 22nd.
The Haitian epidemiologists during their field work had observed sanitary deficiencies at the MINUSTAH camp, including a pipe discharging sewage from the camp into the river. This finding is similar to what was reported by reporter Jonathan Katz during his October 27th visit to the same location (11). Both the Haitian epidemiologists and reporter Katz noted that the villagers regularly used water from the Meye Tributary System for cooking and drinking.
The field investigation continued on October 21st in several wards of the city of Mirebalais. Because their local water supply network was being repaired, the city inhabitants drew their water from the river. There is also a prison in Mirebalais with no exposure to the community other than the river, from which the prisoners drank. In the prison there were 34 cholera cases and four deaths. No other causes of cholera were identified among these prisoners other than drinking river water, downstream from Meille and the Nepalese UN troops (10).
Finally, on October 31st it was observed by the Haitian epidemiologists that sanitary deficiencies in the MINUSTAH camp had been corrected. The repairs took place some time between October 27th (when Katz wrote of his observation) and October 31st. During this time interval, the daily onset of new cholera cases tended to decrease (10). Less clear is the state of the open septic pit at the Mirebalais MINUSTAH camp, where sewage with fecal matter from the Hinche and Terra Rouge MINUSTAH camps was trucked in twice weekly and mixed with Mirebalais sewage in a septic pit. This pit was still seeping sewage into the Meye Tributary of the Artibonite Rive four months later when the UN Panel arrived in February 2011 (3).
In their abstract, Piarroux and his colleagues offer cautious guidance when they state, "our findings strongly suggest that contamination of the Artibonite and one of its tributaries downstream from a military camp triggered the epidemic (10)." They expand on this thought in the Discussion section of their article when stating, "...the exact event that provoked the massive contamination of Lower Artibonite cannot be definitively deduced from an epidemiologic study. Rather, identifying the source and the responsibilities falls within the scope and competence of legal authorities (10)."
Assessment by Legal Authorities
In a court of law, all available findings are considered and presented either to a judge or to a judge and jury. In such judiciary settings, the preponderance of evidence may be sufficient, including the facts and findings presented in this Epilogue. Yet clearly genotyping of the Vibrio cholerae organism from the 2010 outbreak in Nepal would add substantially to the evidence. It would be very helpful if the Nepal government would aid the investigation by opening the doors to the National Public Health Laboratory in Kathmandu. There they would likely find specimens from 2010 collected during the local August-September outbreak. Until this occurs, we are left with the laboratory work that has been reported in this Epilogue and the specimens described in the UN Panel report when they wrote, "genetic typing data on the Nepal strains of Vibrio cholerae O1 isolated between 2007 and 2010 was recently made available to the Independent Panel from the International Vaccine Institute in Korea (Dong Wook Kim, personal communication). The Nepal collection included ... 5 Ogawa strains ...from 2009, and 2 Ogawa strains isolated in 2010 (3)."
While the complete laboratory analysis of the Nepal specimens mentioned in the UN Panel report has not yet been done (or at least not yet published), the UN Panel was able to quickly use the simpler MLVA method in their analysis of the 2009 specimen, occurring a year earlier in Nepal than the epidemic in Haiti. Of this laboratory work they wrote, "a careful analysis of the MLVA results and the ctxB gene indicated that the strains isolated in Haiti (during 2010) and Nepal during 2009 were a perfect match (3)."
It seems likely, based on the preponderance of evidence present in this Epilogue, that there will be corroborating laboratory evidence when analyzing the two Nepalese V. cholerae Ogawa strains from 2010.
Science, Epidemiology and Dr. John Snow
John Snow is both an important historical figure in public health, and a symbol for epidemiologists of the modern disease detective who studies "the distribution and determinants of health related states or events in specified populations" and then applies this knowledge "to control of health problems (13)." Public health professionals and epidemiologists view Snow as a seeker of truth, following scientific footprints to their plausible conclusions, then using this information to ameliorate the problem and improve the health of the population.
The Broad Street Pump Outbreak offers a good example of Snows approach to cholera. When John Snow became convinced by epidemiologic evidence that the Broad Street pump was contaminated by an unseen cholera organism, he went to the responsible government agency and convinced them to remove the handle from the pump, thereby preventing exposure. His evidence for this action was not definitive, since the organism had not yet been identified, but was strongly plausible -- enough for him to encourage public health action. Snow, if blessed with another 160 years of longevity, likely would have acted the same in Haiti, identifying the source of the epidemic and letting the chips fall where they may (that is, letting what happens happen, regardless of the political consequences).
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