Cholera – Exploring a Health Problem Using Descriptive Epidemiologic Approach

HLTH 503 Assignment Instructions

Overview

You will explore a health problem in detail, using a descriptive epidemiologic approach. Through this project, you will gain experience in describing and analyzing the distribution of a health disorder in a population. You will become familiar with various sources of data for the epidemiologic description of a health disorder. In addition, you will enhance the ability to make sound epidemiologic judgments related to public health problems.

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Outline:

Once you have sufficiently researched your topic, develop the following points in an outline format:

  1. Define the problem (nature, extent, significance, etc.).
  2. Describe the agent.
  3. Describe the condition (briefly).
  4. Examine the above sources for data on morbidity and mortality in the selected health problem.
  5. Summarize these data on the distribution of the selected health problem according to the following factors using tables, graphs, or other illustrations whenever possible:
    • Host characteristics
      • Age
      • Sex
      • Nativity
      • Marital status
      • Ethnic group
    • Environmental attributes
      • Geographic areas
      • Social and economic factors
        • Income
        • Housing
      • Occupation
      • Education
    • Temporal variation
      • Secular
      • Cyclic
      • Seasonal
      • Epidemic
    • Any additional characteristic that contributes to an epidemiologic description of the disease
  6. Summarize any current hypotheses that have been proposed to explain the observed distribution.
  7. List the principal gaps in knowledge about the distribution of the health problem.
  8. Suggest areas for further epidemiologic research.
  9. Critically appraise the data as a whole; consult primary sources and important original papers.

Exploring Cholera Using Descriptive Epidemiologic Approach

Defining the Problem

Cholera is a serious and among the oldest recognized infectious disease in human that is caused by vibro (V. cholerae), which is a comma shaped gram-negative bacterium. Cholera is a severe and wide-spread disease and an international health threat. The cholera main symptoms include production of watery, life threatening diarrhea with different levels of dehydration ranging from severe to none. The disease can easily result to death if immediate treatment is not provided to the patient. Cholera is water borne disease which has factually been endemic in various developing nations, particularly in India, Bangladesh, Haiti and some parts of Africa.

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Cholera epidemiological patterns rely greatly on various environmental aspects which include hygiene and sanitation, sanitary conditions, water related behaviors and past immune status of the group at risk. Control efforts have historically centered on increasing safe drinking water availability and case management. Oral cholera vaccine (OCV) that kills whole-cell has been utilized to manage the disease, especially for outbreaks, where swift action is required. Nevertheless, cholera is still a serious concern in public health in endemic countries regardless of our advanced knowledge regarding cholera control mechanisms and epidemiology.

Cholera Agent

Cholera is said to be caused by V. cholera (Vibrio cholerea) strains belonging to O1 biotype EI Tor serogroups and O139 serogroup, which are the main disease agents. V. cholera refers to a slightly curved gram-negative rod and is typified by a single polar flagellum presence, facilitating the bacterium movement.  The strain is said to infect human, both children and adults. Toxigenic V. cholerea is said to produce an enteroxin regarded as cholera toxin (CT), which is responsible for cholera disease manifestation. The V. cholerea comprises of both nonpathogenic and pathogenic strains, varying in their polysaccharide antigens surface and contents of virulence gene, and therefore, among V.cholerae, the O139 and O1 are the two toxigenic serogroups considered as the etiologic serogroups yielding to the disease, which can be pandemic, endemic or epidemic in nature.

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The O1 serogroup is also said to have two biotypes including El Tor and classical, and two major sereotypes that include Inaba and Ogawa, and a third but unstable and rate setotype regarded as Hikojima. The most prevalent sereotype is the ogawa. The El Tor and classical cholera biotypes are the distinct phenotypes which vary with regard to seasonality pattern, infection severity, and aptitude to survive outside the body of the host.

Cholera Condition

Cholera is a bacterial disease that is normally spread via contaminated food and water. The V.cholerae cause severe dehydration and diarrhea such that if not promptly treated, it can be fatal within a short time; causing death. Majority of individuals exposed to V. cholera do not develop illness though they can still shed the bacteria via their stool for a maximum of 14 days, they can still infect others via contaminated water.  The bacteria incubation period varies greatly based on an individual. It thus takes from 12 hours to 5 days for an infected person to demonstrate symptoms. The disease impacts both adults and children.

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Among the individuals who develop symptoms, the majority contain moderate or mild symptoms, though a smaller percentage of the infected people develop severe water diarrhea resulting to dehydration5. Other than watery diarrhea, other visible cholera symptoms include irritability and restlessness, vomiting, metabolic acidosis, increased heart rate, muscles cramps, loss of elasticity of the skin, feeling of thirst, dry mucous membranes, Beside this cholera patients can develop acute electrolyte imbalance, serious renal failure, and coma, resulting to death and hypovolemic shock. Cholera can be epidemic or endemic and its transmission is highly associated to lack adequate sanitation facilities and clean water. Although the statistics shows that about 80% of cholera cases can be treated successfully with oral rehydration solution (ORS), severe cases cannot be managed without antibiotics and intravenous fluids. If untreated, about half of acute cholera cases are fatal, though proper fluid replacement and treatment lower reduce mortality to below 1%. Safe sanitation and water provision is crucial to control cholera transmission among other water borne diseases. In addition safe oral vaccines for cholera need to be employed in conjunction with enhanced sanitation and water for cholera prevention and to manage cholera outbreaks in areas acknowledged to contain high cholera outbreak risk.  

Data of the selected health Problem

Host characteristics

Cholera is a health condition that can affect any human despite of age, gender nativity, marital status or ethnic group. Generally statistics of the host differ from one region to another. While Ghana indicated that majority of the affected people were children and teenagers; individuals below 18 years of age in 2013, Uganda statistics for 2011 indicate that majority affected aged from 15 to 45, with male leading in this population. A research in Bangladesh reveals that most of the affected people in the areas such as Matlab were native people.  

Environmental Attributes

Geographical Areas Research has quantified and postulated the coastal water role in the cholera epidemiology. It has been established that there is large-scale hydro-climatological process influence on cholera prevalence. This implies that, cholera outbreak in most of Lake Basin and along the sea may be associated with the favorable bacterial growth condition.  Although there is no solid explanation on cases of cholera in other regions; away from water bodies, the cholera case are highly frequent especially in Asia particularly in South Asia, Africa especially sub-Sahara Africa, and Latin America. According to who, cholera distribution in Africa based on 2013 statistics is as shown below.

WHO statistics also document that cholera cases were reported in about 38 countries in the world with total of 132121 reported cases. These countries include 17 African countries, 4 European countries, 4 American countries and one Oceania countries. Among them, the United Republic of Tanzania, Haiti, Somalia, the Democratic Republic of Congo (DRC), and Yemen accounted for about 80% of all cholera cases reported in the year. Of all cases recorded worldwide in 2016, 54% documented in Africa, 32% in Hispaniola and 13% in Asia. Nevertheless, not all cases of cholera are documented and hence the cases of cholera worldwide are said to be more than documented. Cholera stands an approximate burden of 21000 to 143000 deaths and 1.4 to 4.0 million cases every year across the world.  

Social and Economic factors

Cholera is regarded as a “forgotten disease” that mostly impacts “forgotten individuals” of the globe. It only discussed when there is a serious cholera outbreak though a few neglected people persistently suffer from cholera recurrent episodes. According to research, cholera risk factors comprise of lack of past exposure, poverty, low education, lack of development, and high population density. Cholera is the major cause of widespread diarrhea in the developing nations with continuing global pandemic in the last 40 years in Latin America, Africa, and Asia. This implies that cholera is associated with poor or low socioeconomic factors, where people living in informal settlements with poor sanitation, poor hygiene and without clean water to drink are likely to experience recurrent cases of cholera. The cholera transmission direct risk factors are those enhancing the feces presence in the environs and its contamination of hands, foods, and water. V. cholera is also known to be a consistent habitat of aquatic environment that is able to live as an aquatic free-living organism. Basic transmission happens between the infected person and permanent aquatic reservoir while secondary transmission happens via human beings faecal oral transmission. Cholera is more common among Lake Basin areas in Africa where families depend on fishing as their main economic activities.

            According to research conducted in Africa which is among the world regions susceptible to cholera particularly in Ghana, the monthly income of the affected population ranges from 10 to 500 US dollars with their expenditure on daily food ranging from 0.5 to 25 US dollars. In addition, majority of the affected people are likely to be living in slums or any other poorly developed housing scheme with characteristics of over population, without sewerage system or clean piped water to drink. The lack of developed sewage system implies that majority in the area do not have toilets or latrines and hence creating a possibility of open defecation. This increases chances of easy V. cholera spread in the area.

Based on the preferred socio-economic features of majority of people affected by cholera as discussed above, it is evident that the disease targets people of low economic ability who may be illiterate or semi-illiterate, and employed in casual jobs or jobs requiring little or no skills and those that are unemployed. Casual job are related to low payment or income, making it hard for those individual to afford good housing, with good sanitation and high living standards characterized by high level of hygiene. The research has identified low education status and high population density as significant cholera risk factor in Bangladesh endemic area.

Temporal Variation

Disease pattern can be influenced by variable factors which include secular trends, cyclic, seasonal trend and epidemic trend. Secular tends are the gradual alterations in the disease frequency over a longer time period. Cyclic trends refer to decrease and increase in the disease frequency or other occurrence within a year or over a number of years. A point of epidemic on the other hand might demonstrate the reaction of a group of individuals restricted in place to a shared source of contamination, and infection among other etiologic aspect to which they were almost simultaneously exposed to. Among the four temporal variations, cholera is more likely to be influenced by epidemics and though seasonal trends of the disease is also highly identifiable.

Various researchers have postulated the cholera temporal variation as due to climatic and environmental factors that impact the seasonal infection patterns. The temporal epidemic and endemic cholera variation has been related to both local and regional environmental forces that include El Nino Southern Oscillation, rainfall patterns, surface temperature, and sea surface. Outbreaks in Bangladesh and Peru have been associated with the periodic El Nino Southern Oscillation climatic cycles. Cholera epidemics in Bangladesh occur twice a year in the fall and spring, after and before the monsoons. Several studies has in addition described a systematic outbreak seasonal cycle in Bangladesh, which include different but specific strains such as O139, El Tor, and classical. Although O139, El Tor, and classical symptoms are similar, some variations in their seasonal cycles are documented. In Bangladesh, classical cholera is said to enter into a dominant seasonal cycle which peaks on later with a newer strains. El Tor is mostly identified from September to November, immediately after the monsoon. A number of studies define this two yearly EL Tor cholera peaks pattern as a minor spring break in April prior to monsoons subsequent by a larger September to December fall outbreak following the monsoon. This pattern is also apparent in other parts of the region. Classical cholera in Pakistan typically upsurges from April to May and from November to January, while seasonal cholera cases in Kolkata, India peak in June, May and April9. Cholera seasonal peaks are also experienced in South America especially during summer and in Amazonia, Brazil during the rainy season. Serious cholera outbreaks are also reported in nations in Eastern Africa which include Tanzania, Djibouti, Uganda, Kenya, and Mozambique, where most of outbreaks happen after floods or rainfall.  

Temporal cholera variation has in addition been associated to variations in nutritional and physical aquatic parameters, including situations in both estuarine and coastal environments. Bangladesh studies have in addition demonstrated environmental relations to V. cholera, which include copepod counts, water depth and temperature, and rainfall. These aspects might contribute to the secular and seasonality trends perceived in outbreaks of cholera. Researchers have observed that both the height and the temperature of sea surface are connected to temporal cholera fluctuations. Researchers in Ghana have observed consistency between resurgences of cholera outbreak and environmental or climatic parameters that include temperature of the land surface, Southern Oscillation and rainfall.

Cholera is an epidemic and endemic disease. The disease epidemics happen covered on endemic illness in long cycles. The cycles are resolute by declining population immunity level and climate variability periods. When such underlying situations are subjected to cholera inexperienced population, a large outbreak is likely to happens like that that happened to Haiti in 2010 stretching to 2011. In epidemic environments, especially where there is no or little natural immunity, all people end up being affected equally despite of age or genders. Cholera epidemics happen unpredictably and they are frequently related to humanitarian emergencies and natural disasters that interrupt access to sanitation and water supplies. Cholera outbreaks related to high mortality and rates of case fatality hardly drops past 1%. The rates of case fatality in 2013of less than 1% were documented in just 4 nations, rates of 1 to 5% were recorded in 17 nations, and that of more than 5% were documented in 5 countries in Africa which included Tanzania, Guinea and Sierra Leone. The high rates of fatality cases stand for health systems deficiencies.

Extra Characteristic which Contributes to an Epidemiologic Description of the Disease

Cholera outbreak is a common phenomenon in most parts of the world, especially among individual with low quality of life. The research estimates that there are around 1.3 million to 4 million cholera cases and 21000 to 143000 cholera related deaths across the world. Cholera disease risk relies on disparities in local environmental contexts and hazards. Individuals are socio-economically susceptible and subsequently biologically vulnerable when there is no income security, due to conflict, via environmental disasters and where rights are denied.

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The collaboration of lack of decent water supplies, poverty, poor housing, high population density, and poor sanitation promote exposure to pathogenic V. cholera. In regions prone to cholera epidemics such as Africa, outbreaks of cholera have been connected to multiple socio-economic and environmental sources. Cholera is said to rapidly diffuse in environments without primary infrastructure that include proper sanitation and access to clean and safe water. The V. cholera can multiply and survive outside the human host and can rapidly spread in settings where people are overcrowded, with no safe disposal of human feces, liquid waste and solid waste.

Summary of any Current Hypotheses that can be proposed to explain the Observed Distribution

Based on the analysis, it is evident that cholera is an epidemic and endemic condition that is highly influenced by seasons and natural disaster. The endemic characteristics are mostly demonstrated in a cyclic or seasonal manner where cholera cases are reported after a certain season. Most cases of cancer are reported along the costal line and lake basins and hence the cholera bacteria are believed to survive in aquatic situation without a human host. Cholera is mostly reported in informal settlements characterized by poor housing, sanitation and poor people with low level of literacy. These settlements are characterized by lack of suitable sewage system and clean piped water to use and drink. The level of hygiene is very low and due to their poor economic status, majority has poor immunity system. The research also demonstrates that only a few people among the infected ones develop cholera symptoms. The data has also demonstrated that majority of cholera cases, both endemic and epidemic are reported in Africa, Latin America and Asia. With this it can be hypothesized that cholera is highly controllable by increasing the living standard of all people in the society. Investing in education and literacy development can play a great role in fighting cholera. It can also be hypothesized that improving people diet to enhance their level of immunity can reduce or completely eliminate cases of cholera in the world. It can also be hypothesized that development of sophisticated sewage system and clean water system in slums and other informal housing sectors can eliminate cases of cholera despite the socio-economic status of the population.

Principal Gaps in Knowledge about the Distribution of the Health Problem

The research gives a great insight into the cases of cholera in the world, focusing more on the endemic and highly epidemic regions. There is also intensive discussion on how endemic cholera episodes happen in countries such as Bangladesh. In this analysis, it was established that people in a country such as Bangladesh experience different seasons of cholera which come with change of cholera strain. Although this aspect has been featured in various research papers, there is still no research work done to explain factors that influence strain change. More information is needed to help in understanding the strain cycles and factors that influence them. With this information, it would be easy for public health departments in Bangladesh to define a strategy to eliminate the underlying factor that influence the change of strain so as to ease the disease management and treatment.

The research in addition demonstrates variation in the host demographic factors influencing the disease development among the infected individuals. Based on the research, about 50% of infected people do not develop the health problem. In addition, there is variation in the age group of the most affected people based on the region. This demonstrates that there is internal human aspect that influences the development of the disease. For instance, a group of 100 people can be infected but only 50 will show the disease symptoms. The research need to determine what factors that influence this trend; demographics or biological and determine what can be done for the rest of the population to acquire similar features so as to lower the rate of infection.

The research also identified that there is a vaccine discovered to control cholera. However, the vaccine has not been extensively used or tested. More knowledge will be needed on the vaccine effectiveness in reducing cholera cases especially in endemic regions. The research should determine the effectiveness of the vaccine even without change of underlying factors that facilitate cholera development such as lack of clean water and sewage system. There is also a knowledge gap on factors influencing endemic cholera in other areas of the world not located along the coast or lake basin. More insight may be needed, also on the average level or duration of V. cholerae survival outside human host; in water or any other habitant; in dry land. This will help in explaining endemic situation on land.

Areas for Further Epidemiologic Research

More research is needed on demographics of the most affected people. This includes precise details on the most vulnerable age, gender, ethnic group and nativity. The current research pays little attention on such matters and only generalizes that the disease affect both adults and children. In addition, the research gives varying information from different demographics from different places.

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However, a closer look at the global statistics can assist in defining a more definite cholera demographic trend in terms of highly affected age, and gender, among other thing. A research is also needed to determine whether there are endemic cycles in sub-Sahara Africa or to ascertain that Africa only records epidemic cases. Other than calamities, a research is needed to determine whether there are cases of cholera in Africa that are not related to calamities such as floods.

Data Critical Appraisal

The research depended on data from secondary research. Most of the used data was drawn from secondary sources which include data recorded during primary research in various regions affected by cholera in Africa, Asia and Latin America. The researches were done at different times and focusing on different aspects. This included data from both quantitative and qualitative researches from credible sources, mostly peer reviewed journals. More data were also obtained from the World Health Organization that keep data on various parts of the world. More data were collected from secondary researches that compile different data from different primary sources to provide an extensive analysis of the disease. There was no primary research conducted in this case, though most of the reviewed data were documented through primary research.

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