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As an epidemiologist, I must make a special note at the beginning of this post. Modern epidemiology has its origin with this disease. It was the study of cholera, particularly in England during the middle of the 19th century, that laid the groundwork for the statistical analysis of public health data and applied surveillance. It was during a time when the miasma theory of disease transmission prevailed in the medical community. The widely recognized anethesiologist, Dr. John Snow, is largely credited with sparking and pursuing a paradigm shift in disease from one which defined illness as borne of bad, malodorous airs, or "miasmas", to one which would begin to recognize disease as infectious. This new conceptualization recognized disease as directly communicable between people or through vehicles (water, in the case of cholera) that are susceptible to contamination by human interaction.
While, Dr. Snow, was indeed at the forefront of pushing this new, germ theory of disease, the credit should not be allocated to him alone for 2 reasons. First, neither he nor any of his contemporaries could identify the agent that caused cholera, or any other disease for that matter, at the time of his investigations. Robert Koch would be the first to isolate and identify in 1877 a bacterial organism, Bacillus anthracis, that was pathogenic for human disease. In 1883, he subsequently identified Vibrio cholerae as the causative agent for cholera. Second, Dr. Snow did not always apply the greatest of rigor in his epidemiological analyses. It would instead be a priest, Henry Whitehead, who would employ exhaustive shoe-leather epidemiology in the Broad Street community as well as taking a more rigorous statistical approach to applied analysis of the resulting data. Dr. Snow's map of the Broad Street cholera outbreak of 1854 and the pump associated with the contaminated well are now iconic symbols of epidemiology and medical geography. This same map, now in the public domain, is the logo for my podcast, The Germlines:
The Pathogen. Cholera is caused by the gram-negative rod-shaped bacterium, Vibrio cholerae. V. cholerae is a distinctively curved (it's often identified as comma-shaped) bacillus with a flagellum:
Pathogenic V. cholerae is actually limited to a subset of strains within the species, rather than extending to all species members. The pathogenic strains are determined by antisera-specific agglutination and are referred to by their serogroup name. Most disease is caused by the O1 and O139 serogroups. Pathogenic V. cholerae are also classified according to biotype, classical or El Tor, and serotype, which consists of two distinct serotypes, Ogawa and Inaba, and one intermediate serotype, Hikojima. Prior to 1992 it was believed that only O1 strains were responsible for causing cholera. However, in 1992 a new serogroup, O139, emerged in South Asia and has been circulating there ever since but has not spread globally thus far. During human infection V. cholerae infects the small intestine and produces a toxin, known as cholera toxin (CT), which is responsible for the diarrheal disease associated with infection. V. cholerae is of only moderate infectivity as hundreds of millions of organisms are required to induce infection, and it is of low pathogenicity since 75% of infections with the classical biotype strains produce mild or subclinical disease and 93% of the El Tor biotype strains produce mild or subclinical disease. However, the virulence can be quite high: case-fatality in resource poor settings typically ranges from 5% to 10%, but can be as high as 20% during some epidemics if appropriate rehydration therapy is not available. In the best of circumstances the case-fatality is approximately 1%.
It is very important to note that Vibrio bacteria, in general, are free-living in water. They occupy various aquatic environments in various geographic locations, though, when free-living, they demonstrate a greater affinity for warmer more tropical climates. Vibrio species can be found in a range of mostly saltwater, and a few freshwater, environs, occupying a distinct ecologic niche in the water column. In addition, because they are ubiquitous in the marine environment they are frequently found in fish, and especially filter-feeding shellfish. Filter feeders (e.g. oysters, clams, cockles) can demonstrate very high levels of colonization, making them a potentially important reservoir for human infection in some circumstances. The image below, published by Nelson et al., 2009, in Nature Reviews Microbiology, shows the generalized V. cholerae life cycle in both the aquatic and human host settings:
While there is a high degree of genetic homogeneity among the various strains of pathogenic V. cholerae, the strains seem to have the ability to experience remarkable changes in specific gene expression as they transfer from the aquatic environment to the human gut. Studies have demonstrated that many of the pathogenic V. cholerae strains exhibit an increase in infectivity of up to 700 fold for up to 18 hours after passing out in the feces. This is a very interesting cross-niche adaption that V. cholerae has evolved to exploit two distinct ecologies (the ocean versus the human gut), while simultaneously relying on the interaction of these two ecologies for the bacterium's success in either one. We will discuss this concept more below.
The Disease. Simply put, it's watery diarrhea. But it is very bad diarrhea. Vomiting is also common.When diarrhea is present, it is a non-dysenteric diarrhea so there is no blood in the stool. Instead cholera diarrhea is characterized by a very liquid and grayish, "rice-water" stool, which can result in rapid and severe dehydration if the fluid loss is untreated. Cholera is really the only diarrheal disease that can cause severe dehydration resulting in death in healthy, immunocompetent adults. The disease is such a danger because so much fluid is lost so quickly: up to 1 liter per hour during acute infections. As such, rehydration therapy with a focus on re-establishing the electrolyte balance is imperative. The characteristic signs of the dehydration that attends the severe diarrhea are sunken eyes and cheeks and poor skin turgor:
The Epidemiology and the Landscape. Each year there are between 3 and 5 million incident cases of cholera globally, with approximately 100,000 associated deaths. Each of these deaths is 100% preventable as they are due to dehydration that can be easily treated with appropriate rehydration therapy. The map below was prepared by the World Health Organization (WHO) and shows the countries reporting annual cholera cases by their average case-fatality. Keep in mind that for any specific cholera epidemic, the actual case-fatality may be much higher depending upon the population affected, the local circumstances, the public health response to the source(s) of exposure, and the resources and knowledge available for rehydration therapy.
Cholera may or may not be an ancient disease. The documentation of this disease in populations largely comes down over the last 200 years through the writings of occupying colonizers of peoples in the tropical latitudes, and India in particular. Whether or not cholera emerged in a single location in the Bay of Bengal, which has been the canon of cholera discourse for generations, or existed endemically in multiple locations throughout the watered geography of the world, we cannot say. Either are possible. However, we can say that, during new periods of intense global shipping traffic due to trade and acquisitions of colonizing nations in the 18th and 19th centuries, cholera did spread globally across the world in a series of seven pandemics. However, the responsibility for this emergent disease and subsequent pandemics resides not in the tropical waters of south Asia or anywhere else, but rather in the large-scale movements of resources and people by the colonizers. I make this distinction because there is a very real discourse defined in the histories of cholera that allocates blame for this burgeoning global disease to subaltern populations. Thus we must read critically the standard documentations and chronologies of the seven pandemics as they are typically described. The first pandemic was referred to as the "Asiatic" cholera pandemic beginning in 1817 and running its course by 1824. The name is quite telling, and was, in part, directly responsible for the bureaucratization of lines between race, and between colonizer and colonized, in an emerging globalized world. This first pandemic extended between the Caspian Sea to the west and China to the east. Each subsequent pandemic lasted typically between 10 and 20 years then retreated into endemicity until the relevant V. cholerae strains were supplanted, thus beginning the next pandemic.
We are currently in the seventh pandemic, which began in 1961 and has been dominated by V. cholerae O1, El Tor. Its geographic spread is documented in this map, which also relied on genome sequencing of the bacterium in spatially diverse samples.
While the new serogroup, O139, emerged in the Bay of Bengal in 1992, this has not led to the emergence of an eighth pandemic.
As natural infection with V. cholerae does confer some immunity for a period, endemicity of infection or previous epidemic exposure is relevant to the severity of new epidemics in a given geographic area. In areas that have not had previous exposure to V. cholerae, essentially the entire population is susceptible. This translates to high incidence among both children and adults. Extremely fast transmission of rapid-onset, severe diarrhea across susceptible populations is characteristic of the typical cholera epidemic, and is one of the reasons why it has historically instilled such fear. A recent tragic example of such a situation is the cholera epidemic in Haiti, which began in 2010. Because cholera had been absent from the country for over a century, virtually everyone was susceptible when exposed. As of the middle of August, 2011, this outbreak had resulted in over 419,000 cases of cholera, of which more than 222,000 have been hospitalized and almost 6000 have died, according to the WHO. Again, explosive outbreaks of severe diarrhea among all age groups in susceptible populations is one of the key epidemiologic features of cholera. This unique dynamic may be due to a combination of a high level of susceptibility in the population with the shift in V. cholerae gene expression that leads to a hyperinfectious state of the bacterium when passed in human feces. Here again is the diagram from above to help illuminate the Vibrio life-cycle in this epidemiologic context:
So, cholera is unique because of the way in which ecologies and environments (particularly water and the human gut) converge to produce potentially massive epidemics. V. cholerae occupies specific ecologic niches, all of which are important in defining the landscape, or aqua-scape, epidemiology of cholera. First, it is free-living in the water column; second, it occupies a reservoir niche in fish and shellfish hosts; third, it occupies a niche in the human intestine, in which it undergoes changes in morphology (the production of the flagellum) and changes in infectivity. As such, its transmission is amplified by orders of magnitude, leading to rapid spread across susceptible populations. But always it's close connection with water is maintained: human fecal contamination of water sources account for the single greatest modality of transmission, and subsequently epidemic spread. Therefore, cholera is also firmly grounded in the human social landscape, being sharply delineated by the personal practice of hygiene at the level of the household and the public health practice of infrastructural sanitation at the level of the municipality.
Treatment. Oral rehydration salts mixed with water provide a universal and highly effective treatment. The goal is to reestablish the electrolyte balance in the person suffering the diarrhea episode. In order to stave off what can develop into deadly dehydration (in the case of cholera this can happen in a matter of hours), the individual must replace the fluid lost, AND the salts lost. This is precisely the goal of oral rehydration therapy. Packets of oral rehydration salts containing sodium chloride, potassium chloride, citrate and glucose can be obtained from almost any pharmacist or chemist in most areas of the world. These are simply mixed with water and consumed by the diarrhea-afflicted person. In addition, as much as can be tolerated by the ill person, normal nutrition intake should be maintained throughout the diarrhea episode. It may seem as though the food will go right through you, but the body does obtain some nutrients and this helps the immune system fight the infection. If dehydration is advanced, and/or if the individual is unable to keep fluids down due to vomiting, then intravenous administration of fluids will likely be necessary. With proper rehydration, no one should die from cholera.
Those suffering from cholera who are undergoing rehydration therapy should be closely monitored for fluid loss during the diarrhea illness. This is typically accomplished using a cholera cot, which is a basic cot with a plastic sheet covering and a hole in the middle that drains into a bucket placed below the hole:
This bucket should contain a measuring stick that quantifies the volume of fluid lost. In this way, health care providers can monitor the volume of fluid loss over time so rehydration therapy can be optimized.
Prevention and Control. Good sanitation and hygiene are the foundation of cholera prevention. Indeed, public sanitation and public health are both directly derived from the response to cholera in the latter half of the 19th century. However, even after more than 150 years, the world has not yet achieved anything close to an equitable distribution of safe water and so cholera epidemics can still strike with great force, as in Haiti in 2010 or in Zimbabwe in 2008. As such, improved infrastructure that can maintain adequate water resources is a first priority in cholera prevention. Secondarily, personal hygiene at the individual level of the household can also be very important in preventing the spread of cholera: consistent hand washing, boiling water, and thoroughly cooking food are all important in stopping the chain of transmission. However, these latter individual efforts, of course, require that adequate resources exist for such practices. Since both water and fuel for cooking or boiling water are often in short supply in the areas most at risk for widespread epidemics, these practices can be difficult to implement.
Finally, it is important to note that shellfish can be an important reservoir for cholera even in developed countries and should therefore be cooked thoroughly before eating. V. cholerae is endemic along the Gulf Coast of the United States and regular cases of cholera are seen in this area due to eating contaminated shellfish that have not been properly cooked. These isolated cases have not resulted in widespread epidemics because of the effective sanitation infrastructure in place along the Gulf Coast, which keeps any individual infections from contaminating larger water sources.
Here is a very nice animated video by the Department of Entomology at the University of Illinois demonstrating some cholera prevention strategies:
As an epidemiologist, I must make a special note at the beginning of this post. Modern epidemiology has its origin with this disease. It was the study of cholera, particularly in England during the middle of the 19th century, that laid the groundwork for the statistical analysis of public health data and applied surveillance. It was during a time when the miasma theory of disease transmission prevailed in the medical community. The widely recognized anethesiologist, Dr. John Snow, is largely credited with sparking and pursuing a paradigm shift in disease from one which defined illness as borne of bad, malodorous airs, or "miasmas", to one which would begin to recognize disease as infectious. This new conceptualization recognized disease as directly communicable between people or through vehicles (water, in the case of cholera) that are susceptible to contamination by human interaction.
While, Dr. Snow, was indeed at the forefront of pushing this new, germ theory of disease, the credit should not be allocated to him alone for 2 reasons. First, neither he nor any of his contemporaries could identify the agent that caused cholera, or any other disease for that matter, at the time of his investigations. Robert Koch would be the first to isolate and identify in 1877 a bacterial organism, Bacillus anthracis, that was pathogenic for human disease. In 1883, he subsequently identified Vibrio cholerae as the causative agent for cholera. Second, Dr. Snow did not always apply the greatest of rigor in his epidemiological analyses. It would instead be a priest, Henry Whitehead, who would employ exhaustive shoe-leather epidemiology in the Broad Street community as well as taking a more rigorous statistical approach to applied analysis of the resulting data. Dr. Snow's map of the Broad Street cholera outbreak of 1854 and the pump associated with the contaminated well are now iconic symbols of epidemiology and medical geography. This same map, now in the public domain, is the logo for my podcast, The Germlines:
The Pathogen. Cholera is caused by the gram-negative rod-shaped bacterium, Vibrio cholerae. V. cholerae is a distinctively curved (it's often identified as comma-shaped) bacillus with a flagellum:
Pathogenic V. cholerae is actually limited to a subset of strains within the species, rather than extending to all species members. The pathogenic strains are determined by antisera-specific agglutination and are referred to by their serogroup name. Most disease is caused by the O1 and O139 serogroups. Pathogenic V. cholerae are also classified according to biotype, classical or El Tor, and serotype, which consists of two distinct serotypes, Ogawa and Inaba, and one intermediate serotype, Hikojima. Prior to 1992 it was believed that only O1 strains were responsible for causing cholera. However, in 1992 a new serogroup, O139, emerged in South Asia and has been circulating there ever since but has not spread globally thus far. During human infection V. cholerae infects the small intestine and produces a toxin, known as cholera toxin (CT), which is responsible for the diarrheal disease associated with infection. V. cholerae is of only moderate infectivity as hundreds of millions of organisms are required to induce infection, and it is of low pathogenicity since 75% of infections with the classical biotype strains produce mild or subclinical disease and 93% of the El Tor biotype strains produce mild or subclinical disease. However, the virulence can be quite high: case-fatality in resource poor settings typically ranges from 5% to 10%, but can be as high as 20% during some epidemics if appropriate rehydration therapy is not available. In the best of circumstances the case-fatality is approximately 1%.
It is very important to note that Vibrio bacteria, in general, are free-living in water. They occupy various aquatic environments in various geographic locations, though, when free-living, they demonstrate a greater affinity for warmer more tropical climates. Vibrio species can be found in a range of mostly saltwater, and a few freshwater, environs, occupying a distinct ecologic niche in the water column. In addition, because they are ubiquitous in the marine environment they are frequently found in fish, and especially filter-feeding shellfish. Filter feeders (e.g. oysters, clams, cockles) can demonstrate very high levels of colonization, making them a potentially important reservoir for human infection in some circumstances. The image below, published by Nelson et al., 2009, in Nature Reviews Microbiology, shows the generalized V. cholerae life cycle in both the aquatic and human host settings:
The Disease. Simply put, it's watery diarrhea. But it is very bad diarrhea. Vomiting is also common.When diarrhea is present, it is a non-dysenteric diarrhea so there is no blood in the stool. Instead cholera diarrhea is characterized by a very liquid and grayish, "rice-water" stool, which can result in rapid and severe dehydration if the fluid loss is untreated. Cholera is really the only diarrheal disease that can cause severe dehydration resulting in death in healthy, immunocompetent adults. The disease is such a danger because so much fluid is lost so quickly: up to 1 liter per hour during acute infections. As such, rehydration therapy with a focus on re-establishing the electrolyte balance is imperative. The characteristic signs of the dehydration that attends the severe diarrhea are sunken eyes and cheeks and poor skin turgor:
Usually 2% - 5% body fluid loss is required before dehydration is clinically recognizable. In addition to the sunken eyes and poor skin turgor mentioned above, irritability, thirst, increased heart rate and respiration, and no urine volume are also characteristic of this stage. A 10% loss of body fluid marks severe dehydration and is characterized by low blood pressure, diminished pulse, increasingly poor skin turgor, delirium, and frequent loss of consciousness. At this stage the individual is no longer eager to drink and may not even be able to do so. This constitutes a medical emergency and requires immediate oral or intravenous (usually the latter) rehydration therapy.
The Epidemiology and the Landscape. Each year there are between 3 and 5 million incident cases of cholera globally, with approximately 100,000 associated deaths. Each of these deaths is 100% preventable as they are due to dehydration that can be easily treated with appropriate rehydration therapy. The map below was prepared by the World Health Organization (WHO) and shows the countries reporting annual cholera cases by their average case-fatality. Keep in mind that for any specific cholera epidemic, the actual case-fatality may be much higher depending upon the population affected, the local circumstances, the public health response to the source(s) of exposure, and the resources and knowledge available for rehydration therapy.
Cholera may or may not be an ancient disease. The documentation of this disease in populations largely comes down over the last 200 years through the writings of occupying colonizers of peoples in the tropical latitudes, and India in particular. Whether or not cholera emerged in a single location in the Bay of Bengal, which has been the canon of cholera discourse for generations, or existed endemically in multiple locations throughout the watered geography of the world, we cannot say. Either are possible. However, we can say that, during new periods of intense global shipping traffic due to trade and acquisitions of colonizing nations in the 18th and 19th centuries, cholera did spread globally across the world in a series of seven pandemics. However, the responsibility for this emergent disease and subsequent pandemics resides not in the tropical waters of south Asia or anywhere else, but rather in the large-scale movements of resources and people by the colonizers. I make this distinction because there is a very real discourse defined in the histories of cholera that allocates blame for this burgeoning global disease to subaltern populations. Thus we must read critically the standard documentations and chronologies of the seven pandemics as they are typically described. The first pandemic was referred to as the "Asiatic" cholera pandemic beginning in 1817 and running its course by 1824. The name is quite telling, and was, in part, directly responsible for the bureaucratization of lines between race, and between colonizer and colonized, in an emerging globalized world. This first pandemic extended between the Caspian Sea to the west and China to the east. Each subsequent pandemic lasted typically between 10 and 20 years then retreated into endemicity until the relevant V. cholerae strains were supplanted, thus beginning the next pandemic.
We are currently in the seventh pandemic, which began in 1961 and has been dominated by V. cholerae O1, El Tor. Its geographic spread is documented in this map, which also relied on genome sequencing of the bacterium in spatially diverse samples.
Transmission events inferred for the seventh cholera pandemic phylogenetic tree drawn on a global map
While the new serogroup, O139, emerged in the Bay of Bengal in 1992, this has not led to the emergence of an eighth pandemic.
As natural infection with V. cholerae does confer some immunity for a period, endemicity of infection or previous epidemic exposure is relevant to the severity of new epidemics in a given geographic area. In areas that have not had previous exposure to V. cholerae, essentially the entire population is susceptible. This translates to high incidence among both children and adults. Extremely fast transmission of rapid-onset, severe diarrhea across susceptible populations is characteristic of the typical cholera epidemic, and is one of the reasons why it has historically instilled such fear. A recent tragic example of such a situation is the cholera epidemic in Haiti, which began in 2010. Because cholera had been absent from the country for over a century, virtually everyone was susceptible when exposed. As of the middle of August, 2011, this outbreak had resulted in over 419,000 cases of cholera, of which more than 222,000 have been hospitalized and almost 6000 have died, according to the WHO. Again, explosive outbreaks of severe diarrhea among all age groups in susceptible populations is one of the key epidemiologic features of cholera. This unique dynamic may be due to a combination of a high level of susceptibility in the population with the shift in V. cholerae gene expression that leads to a hyperinfectious state of the bacterium when passed in human feces. Here again is the diagram from above to help illuminate the Vibrio life-cycle in this epidemiologic context:
So, cholera is unique because of the way in which ecologies and environments (particularly water and the human gut) converge to produce potentially massive epidemics. V. cholerae occupies specific ecologic niches, all of which are important in defining the landscape, or aqua-scape, epidemiology of cholera. First, it is free-living in the water column; second, it occupies a reservoir niche in fish and shellfish hosts; third, it occupies a niche in the human intestine, in which it undergoes changes in morphology (the production of the flagellum) and changes in infectivity. As such, its transmission is amplified by orders of magnitude, leading to rapid spread across susceptible populations. But always it's close connection with water is maintained: human fecal contamination of water sources account for the single greatest modality of transmission, and subsequently epidemic spread. Therefore, cholera is also firmly grounded in the human social landscape, being sharply delineated by the personal practice of hygiene at the level of the household and the public health practice of infrastructural sanitation at the level of the municipality.
Treatment. Oral rehydration salts mixed with water provide a universal and highly effective treatment. The goal is to reestablish the electrolyte balance in the person suffering the diarrhea episode. In order to stave off what can develop into deadly dehydration (in the case of cholera this can happen in a matter of hours), the individual must replace the fluid lost, AND the salts lost. This is precisely the goal of oral rehydration therapy. Packets of oral rehydration salts containing sodium chloride, potassium chloride, citrate and glucose can be obtained from almost any pharmacist or chemist in most areas of the world. These are simply mixed with water and consumed by the diarrhea-afflicted person. In addition, as much as can be tolerated by the ill person, normal nutrition intake should be maintained throughout the diarrhea episode. It may seem as though the food will go right through you, but the body does obtain some nutrients and this helps the immune system fight the infection. If dehydration is advanced, and/or if the individual is unable to keep fluids down due to vomiting, then intravenous administration of fluids will likely be necessary. With proper rehydration, no one should die from cholera.
Those suffering from cholera who are undergoing rehydration therapy should be closely monitored for fluid loss during the diarrhea illness. This is typically accomplished using a cholera cot, which is a basic cot with a plastic sheet covering and a hole in the middle that drains into a bucket placed below the hole:
This bucket should contain a measuring stick that quantifies the volume of fluid lost. In this way, health care providers can monitor the volume of fluid loss over time so rehydration therapy can be optimized.
Prevention and Control. Good sanitation and hygiene are the foundation of cholera prevention. Indeed, public sanitation and public health are both directly derived from the response to cholera in the latter half of the 19th century. However, even after more than 150 years, the world has not yet achieved anything close to an equitable distribution of safe water and so cholera epidemics can still strike with great force, as in Haiti in 2010 or in Zimbabwe in 2008. As such, improved infrastructure that can maintain adequate water resources is a first priority in cholera prevention. Secondarily, personal hygiene at the individual level of the household can also be very important in preventing the spread of cholera: consistent hand washing, boiling water, and thoroughly cooking food are all important in stopping the chain of transmission. However, these latter individual efforts, of course, require that adequate resources exist for such practices. Since both water and fuel for cooking or boiling water are often in short supply in the areas most at risk for widespread epidemics, these practices can be difficult to implement.
Finally, it is important to note that shellfish can be an important reservoir for cholera even in developed countries and should therefore be cooked thoroughly before eating. V. cholerae is endemic along the Gulf Coast of the United States and regular cases of cholera are seen in this area due to eating contaminated shellfish that have not been properly cooked. These isolated cases have not resulted in widespread epidemics because of the effective sanitation infrastructure in place along the Gulf Coast, which keeps any individual infections from contaminating larger water sources.
Here is a very nice animated video by the Department of Entomology at the University of Illinois demonstrating some cholera prevention strategies:
In response to the post, I must say that for over 150 years this disease has known to exist and we understand the mechanism by which it is transmitted, we have the technology available and yet 200,000 people still die because of cholera. Is the technology to clean water accessible? The factors of proper resource allocation and prepardness on the part of government must be enhanced. Poor infrastucture is also a major problem as well.
ReplyDeleteI commend the fieldwork that is done by players in the immediate surveillance, monitoring and treatment during a cholera outbreak because the disease can spread so rapidly and must place an immense amount of pressure on those individuals to save lives and stop it in its tracks.
I believe cholera has been in the news recently out of Somalia. As of 2 weeks ago 37 lives were lost due to the disease...
Pakistan faced a flood crisis last year in 2010 and the spread of cholera became a threat. Since previous exposure to a disease is related to the severity of an outbreak, I'm wondering if the incidence of cases was lower in Pakistan than other countries that had faced a similar threat because of its proximity to the Bay of Bengal, where cholera may have arose from.
ReplyDeleteTo go along with this post, I am wondering what steps global health organizations (the WHO, for example) or governments are doing to prepare for a Cholera outbreak of the new strain, O139, discovered in 1992? The new strand, found in Southeast Asia, seems to be the 8th pandemic waiting to release itself on the world. Even in developed nations, the impact that a cholera outbreak could have huge ramifications, in terms of deaths and hospitalizations, as well as financial burden on healthcare systems. Taking steps to mitigate the effects of preventable disease, such as cholera, needs to be done globally and nations need to support one another in preventing these outbreaks in more susceptible regions.
ReplyDeleteAnother point to make is the Haiti outbreak that is still occurring. Although the consensus is that the outbreak was not due to the catastrophic earthquake the nation suffered, it brings one question: How can a nation protect itself from diseases such as cholera in times of national disasters? Even if there is no direct relationship between the earthquake and outbreak, the effect on the infrastructure of the medical care in Haiti was surely catastrophic and led to issues in treating the outbreak.
The trouble facing the spread of cholera is the same observed in many diseases. When the threat is not obvious people do very little in the way of prevention. People may become lax about hand washing, waste disposal, or the cleanliness of their water supply. Resources may not be allocated to emergency preparedness for events such as cholera outbreaks. These factors, in addition to the increased number of susceptible people in the population (who have never been exposed) can aid the rapid spread of the disease. Improvements in infrastructure, preparedness, and the implementation of health education programs are necessary for preventing the spread of not just cholera, but most (if not all) communicable diseases.
ReplyDeleteSince "extremely fast transmission of rapid-onset, severe diarrhea across susceptible populations is characteristic of the typical cholera epidemic," surveillance systems seem to be an essential component in mitigating the incidence rates and severity of cholera epidemics. Without a robust active surveillance system, treatment and prevention responses would be slow to act thus needlessly increasing mortality. Is the surveillance of cholera the responsibility of each country or global institutions such as the WHO?
ReplyDeleteIn the Cholera post, I found it very interesting how the organism survives in the environment, and how it depends on the human social aspect and the infrastructure of a country to thrive. After the earthquake hit Haiti in 2010, the already failing infrastructure of the country collapsed even more giving more grounds for cholera to proliferate. When I visited 3 months after it occurred, the living conditions there were unbearable and in some areas unlivable. Many of the countryside consisted of tents 3 feet in width, improper bathrooms, and unclean water system. I wondered then and still do now, if the country was so susceptible to infection after the earthquake, why was there not more focus on expediting the rebuilding process of the living conditions to ensure a safer environment for the people of Haiti? Also, what steps can we take to ensure that countries with weak infrastructures have access to clean water in a disaster, natural or unnatural? Only 3 months after the earthquake, many locals were already being plagued by minor infections, and yet the proper aid was still not available to them. Visually, there was not a great effort in place to avoid or lessen the cause of the cholera epidemic in Haiti, and in countries such as Haiti and other lower economic countries there should always be a plan of action to maintain a clean water supply system and septic system. I do realize that this is the situation in a perfect world, however, outbreaks such as cholera would be less of a threat. The cholera epidemic in Haiti should encourage Haiti's government and other surrounding countries to strengthen their infrastructure before it contributes or re-contributes to an infectious outbreak.
ReplyDeleteIt is interesting and poignant that a cholera outbreak lead to the birth of epidemiology. Cholera is more than an isolated organism with the potential to wreak havoc and cause tremendous loss of life in a community. A cholera outbreak is also a manifestation of the fundamental problems in the public health infrastructure of a community. Do major outbreaks even occur in communities in the modern era that have access to clean water, and that have both adequate disease surveillance and health care resources? Should I never eat a raw oyster again?
ReplyDeleteWhen it comes to cholera, it seems the most susceptible populations are ones where nutrition itself would not be easy to obtain. While I agree that maintaining adequate nutrition is essential to recovering from any illness, I'm wondering how much it should be stressed in a situation where it's not easily available- seeing that chronic diarrhea severely limits the amount that can actually be absorbed.
ReplyDeleteChris said "To go along with this post, I am wondering what steps global health organizations (the WHO, for example) or governments are doing to prepare for a Cholera outbreak of the new strain, O139, discovered in 1992? The new strand, found in Southeast Asia, seems to be the 8th pandemic waiting to release itself on the world. Even in developed nations, the impact that a cholera outbreak could have huge ramifications, in terms of deaths and hospitalizations, as well as financial burden on healthcare systems. Taking steps to mitigate the effects of preventable disease, such as cholera, needs to be done globally and nations need to support one another in preventing these outbreaks in more susceptible regions.
ReplyDeleteAnother point to make is the Haiti outbreak that is still occurring. Although the consensus is that the outbreak was not due to the catastrophic earthquake the nation suffered, it brings one question: How can a nation protect itself from diseases such as cholera in times of national disasters? Even if there is no direct relationship between the earthquake and outbreak, the effect on the infrastructure of the medical care in Haiti was surely catastrophic and led to issues in treating the outbreak."
Chris,
I know that in Somalia UNICEF has been playing a role in trying to mitigate the burden that Cholera is having on children there. UNICEF being a large, international collaboration continues to monitor the situation there.
visit here: http://www.unicef.org/infobycountry/somalia_59602.html
I agree with you that the burden of Vibrio Cholera should be fought on an international and global level because it is a global disease. It is not endemic just to one region.
In reference to disasters and associated outbreaks of cholera, I think it all comes down to resources and preparedness. Resources such as proper infrastructure, sanitation, health delivery etc. And then strategy and preparedness to anticipate disaster and react to massive outbreak... So there are regions of the world that are much more susceptible to mother nature's fury, so international and domestic support I think are needed to plan out and coordinate when and if an outbreak occurs what the best way is of reducing future burden. but you just never know how bad you'll get hit or when (if its an earthquake).
focus should be on preparedness.
I believe that cholera is an excellent example of the importance of health education. Chris asks how can a nation protect itself from disease in times of natural disasters? And Anika asks what steps can be taken to ensure that communities have access to clean water?
ReplyDeleteI say that educated communities are very important in dealing with both of these issues.
Through education, people know to use clean water, wash their hands, and to use a toilet or dispose of their waste by other sanitary means.
There are many things that may seem so common sense to us, but are not properly understood in other communities.
I'll suggest this article from UNICEF that demonstrates what some educational programs have done in Haiti.
http://www.unicef.org/emerg/haiti_57135.html
This program promotes breastfeeding. Prior to this program many mothers believed that the earthquake had affected their breast milk and that it would harm their babies so they stopped breastfeeding, putting their infants at risk for cholera.
Am I suggesting that education will do away with cholera? No, but it can definitely mitigate the number of cases and burden of the disease.
I agree with Waqas in that surveillance systems are crucial in decreasing the incidence and severity of cholera. I believe that the responsibility of cholera surveillance should be a collective effort between each country, the CDC, and/or the WHO. For example, the Pan American Health Organization analyzes and communicates surveillance data to the CDC from Latin America and the Caribbean. Surveillance data includes cholera as well as other diseases. With such an integration of surveillance systems, therefore, resources may be allocated to areas most in need and further action can be taken to improve overall living conditions. Each country can voice what its people need most and further action can be taken to prevent the spread of communicable diseases.
ReplyDeleteI agree with George's post about mentioning that a disease with such a long history has allowed us to learn so much about it in regards to where it came from, and how to treat and prevent it. We have so much technology around the world, most that is not even accessible to the public, that can provide clean water and all of the necessary resources to prevent cholera outbreaks. A proper surveillance system should be put into place to prevent any further outbreaks with cholera or other infectious diseases. Andriane had pointed out how Latin America and the Caribbean communicates information from their surveillance systems, and how the information gathered should be a collective effort. This makes a great deal of sense, because if every country had access to all of the information gathered, that particular country's infrastructure will become increasingly stronger in their knowledge and action of preventing cholera.
ReplyDeleteDiscussing this issue of access to technology and the basic resources brings me back to the infamous question: Is clean water a right or a privilege, and who is that decision maker?
Simple hand washing with soap and water and adequate municipal sanitation are very important measures in the prevention of Vibrio Cholera infection. Sounds simple, but may be difficult to implement. Cholera is a diarrheal disease that should be relatively easily preventable. Children must be taught at an early age about the importance of hand washing in preventing many diseases, including cholera; however, to make the largest impact in saving thousands of lives yearly is to provide adequate sanitation and clean water to people in every community. Having clean water is the better way to save lives in the masses. One example of prevention on a large scale is when fluoride was routinely added to water in developed countries. This has significantly reduced the amount of tooth decay, compared to relying on personal hygiene alone. Effective sanitation along with hand hygiene, boiling water prior to use and thoroughly cooking foods, especially sea food, can prevent cholera infection and possibly eliminate or even eradicate it altogether.
ReplyDeleteI agree with Nicole on the fact that health education is an important tool in prevention of the disease. I also agree with what Stella said about simple ways to prevent Cholera. I heard that treating water with a few drops of household bleach can make it safe to use and drink. This is a relatively inexpensive method of prevention that could work on a community level (one bottle of bleach per community?).
ReplyDeleteTo answer Waqas Shaikh's question, I believe it is the responsibility of each country to implement surveillance measures to prevent and control cholera outbreaks. Ultimately each country is responsible for its citizens, but global institutions such as WHO must support the efforts of the countries with poor infrastructure and the highest incidence rates of cholera. Epidemic outbreaks may affect regions, but can quickly spread to many parts of the world. The world is a "global village" and we must work together to save lives from preventable diseases such as cholera.
ReplyDeleteJen brought up some good points earlier about the difficulty of obtaining nutrition during a cholera outbreak. Because of the sheer necessity for people to obtain nutrients when facing such severe diarrhea, I believe a main focus of the WHO, UNICEF, public health agencies, and governments should be on the planning of administering oral rehydration salts during such an outbreak for countries that are not already prepared to do so and for countries that are in need of reevaluation of the current effectiveness of access to these salts. The WHO has expressed on their website that 80% of cholera cases can be treated with oral rehydration salts and considering the relative effectiveness and feasibility of stocking up on these tablets, I believe preparing a supply of these salts should be a major concern.
ReplyDeleteI agree with Nicole. Like other diseases, cholera is mainly spread because of poor water sanitation systems. Proper and clean sanitation is a basic and key component of any health community. Building and maintaining proper sanitation systems will pay dividends not only for preventing cholera but other diarrheal and fecal-oral transmitted diseases. Thus, I think more resources should be devoted to primary prevention interventions such as proper water sanitation instead of secondary and tertiary prevention interventions.
ReplyDeleteBobbin - Your response to Jen's comment about the difficulty in attaining nutrient during the outbreak only accounts for areas where there are local health officials that can keep stores of oral rehydration salts.
ReplyDeleteIf an outbreak occurs in an area with no immediate access to these resources then you will still have people dying and spreading the disease. The world health infrastructure is not strong enough to ensure that every cholera case will be treated properly.
This an other example of a disease that is caused by poor sanitary and living conditions and uncooked mea in this case shellfish. during the last outbreak of cholera in Haiti, people die from a lack of hydration and antibiotics (even though cases were identified early)thatis there were a shortage of IV fluid and medication. Simple precautionary measures such as boiling water and eat well cooked shellfish can tremendously redure the cholera
ReplyDeleteI find the change in gene expression that takes place in the human gut extremely fascinating! Does this have to do with the bacteria communicating with one another? A year ago I would have thought this question was sic-fi nonsense, but there is some amazing research about bacterial communication happening right now. (If you are interested check out: http://www.youtube.com/watch?v=TVfmUfr8VPA)
ReplyDeleteIf they are "talking," could we develop drugs that block their communication and use them prophylactically in outbreaks?
The gene expression that varies in among V. cholera probably has to do with mutations that occurs. I am also wondering if these organisms can alter their genome via conduction and would therefore need an f+ factor. Since a infected person usually exhibits a 700 fold for up to 18 hours after passing out in the feces the mutations and other forms of genetic alterations would occur quickly. Since it is very difficult if not impossible to eradicate this disease - I agree with Ricardo Guervil that the best warfare to employ is the use of clean water and the proper sanitation.
ReplyDeleteAlso, I have learned about this disease in many of my public health classes and was only aware of Dr. Snow's contribution and was not aware of Robert Koch who isolated and identified the human strain (Bacillus anthracis) and also identified the causative agent. I found this to be very interesting and am wondering why he has not gained any notoriety in connection to Cholera.