Intervention studies and the definition of dominant transmission routes
TL;DR: The implications for the analysis of real-world data are analyzed by examining data on the importance of water and other transmission routes for cholera in Bangladesh by using a quantitative model to generate synthetic data.
Abstract: A common approach to assessing the relative importance of different transmission routes is to eliminate transmission through one route and assume that the ratio "number of cases eliminated:number of residual cases" measures the relative importance of the eliminated route vis-a-vis the residual transmission route. A quantitative model is used to generate synthetic data similar to those analyzed by epidemiologists. These data are analyzed using this conventional procedure and the inferences drawn from the synthetic data compared with the causal relationships structured into the model. The implications for the analysis of real-world data are analyzed by examining data on the importance of water and other transmission routes for cholera in Bangladesh.
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TL;DR: In this article, the authors examined the impact of piped water on the under-1 infant mortality rate (IMR) in Brazil using a novel econometric procedure for the estimation of quantile treatment effects with panel data.
Abstract: We examine the impact of piped water on the under-1 infant mortality rate (IMR) in Brazil using a novel econometric procedure for the estimation of quantile treatment effects with panel data. The provision of piped water in Brazil is highly correlated with other observable and unobservable determinants of IMR -- the latter leading to an important source of bias. Instruments for piped water provision are not readily available, and fixed effects to control for time invariant correlated unobservables are invalid in the simple quantile regression framework. Using the quantile panel data procedure in Chen and Khan (2007), our estimates indicate that the provision of piped water reduces infant mortality by significantly more at the higher conditional quantiles of the IMR distribution than at the lower conditional quantiles (except for cases of extreme underdevelopment). These results imply that targeting piped water intervention toward areas in the upper quantiles of the conditional IMR distribution, when accompanied by other basic public health inputs, can achieve significantly greater reductions in infant mortality.
13 citations
TL;DR: Household level behavioural factors such as storage practises should not be analysed in isolation as determinants of diarrhoeal illness particularly when pitted against stronger neighbourhood and external determinants.
Abstract: While infrastructure conditions constitute 'primary routes', contamination of water within households and other behavioural determinants are considered as 'secondary routes'. However, recontaminated water has been considered not to constitute a serious risk though it occurs commonly in poorer societies. A study was conducted in Delhi where individual risk factors were located within a larger socio-economic, political and administrative framework, as they were often independent variables. This component of the larger study hypothesised that behavioural factors at individual household levels lose significance as major determinants of diarrhoeal diseases once they are analysed in a holistic epidemiology frame. Determinants at the household level were explored through a dataset based on a primary survey of 300 households in three slum clusters. Amongst households storing municipal water (proven to be safe at source), adhering to the best storage practices did not translate into lower incidence rates as compared to those with relatively unsafe practices. The explanation lay in factors which were external to the home and beyond the control of the affected household. Thus, household level behavioural factors such as storage practises should not be analysed in isolation as determinants of diarrhoeal illness particularly when pitted against stronger neighbourhood and external determinants.
13 citations
Dissertation•
01 Jul 2014
TL;DR: In this article, the authors assessed the costs and benefits distribution of improving drinking water quality through a land set-aside payment for ecosystem services (PES) scheme in a watershed of Honduras.
Abstract: This thesis assessed the costs and benefits distribution of improving drinking water quality through a land set-aside payment for ecosystem services (PES) scheme in a watershed of Honduras. The benefits of improving drinking water quality were determined using a contingent valuation survey for a stated willingness-to-pay (WTP) for improved drinking water quality through a PES scheme; and a revealed WTP was determined as the sum of averting expenditure and illness damage costs. Likewise, the costs of water conservation were determined through two approaches, the flow and rent opportunity costs of upstream landholders.
Both WTP measures evidenced that beneficiaries could afford and were willing to pay for improved drinking water quality. The two WTP measures were not correlated, but this could be due to biased estimates or context-dependent preferences for each approach. Conversely, the cost of water conservation came to an overall flow net return of US$ 1,410 ha-1, with coffee exhibiting the highest returns. However, the median positive returns without coffee, US$ 140, are used and they are correlated to the rent opportunity costs. Identifying a reliable, accurate and cost-effective method to determine opportunity costs is challenging, but the two methods employed provided valid estimates. This study identifies and discusses several distributional issues for PES schemes; these are the upstream-downstream externality framework, peoples’ perceptions, unequal water governance, and fair targeting of payments to service providers.
The WTP for improved drinking water quality is not sufficient to compensate the opportunity costs of landholders. The WTP would only cover 6% to 10% of the estimated cost of the water conservation. Thus, a user-based PES scheme at the study site is not feasible. Water conservation is more likely to be possible if substantial external support is obtained or through a sustainable land management-based scheme.
10 citations
Cites background from "Intervention studies and the defini..."
...account in assessing the impact of any single intervention to control diarrhoea (Briscoe, 1984; Dasgupta, 2004)....
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...This study recognizes that the transmission routes of diarrhoea causing pathogens is quite complex and has to be taken into 2 6 0 124 account in assessing the impact of any single intervention to control diarrhoea (Briscoe, 1984; Dasgupta, 2004)....
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25 Jan 2008
TL;DR: The extent to which WSS projects cite potential health benefits in design documents; include explicit objectives with respect to improving health outcomes; target environmental improvements that are likely to provide health benefits; and collect evidence on changes in health outcomes is reviewed.
Abstract: This paper reviews the contribution of the World Bank's water supply and sanitation (WSS) lending portfolio to improving health outcomes, in general and among the poor, as background for the Independent Evaluation Group (IEG) evaluation of the Bank's support for health, nutrition, and population (HNP). Over the past decade (FY97-06), the World Bank committed more than $7.2 billion to 117 new WSS projects in six developing regions, managed by the WSS Sector Board. This paper reviews the extent to which these projects: cite potential health benefits in design documents; include explicit objectives with respect to improving health outcomes; target environmental improvements that are likely to provide health benefits; target services and health or behavioral outcomes among the poor; and collect evidence on changes in health outcomes. A review of the lending portfolio over the past decade reveals very little about the health benefits of the World Bank's WSS investments. Significant improvements in health outcomes are possible through improvements in water supply, sanitation, and hygiene, though they should not be assumed to benefit the poor. Half of the WSS projects approved in the past decade cited potential health benefits that are, implicitly they had a health objective, and 89 percent financed infrastructure that plausibly could have improved health.
10 citations
TL;DR: Comparison of the tryptic digest of R7K with native CT suggested that changes in protein conformation may be responsible for the loss of ADP-ribosylation activity, but modified proteins in which arginine 7 was replaced with lysine 7 exhibited undetectable ADP ribosyltransferase activity were generated.
10 citations
Cites background from "Intervention studies and the defini..."
...Other routes of infection include ingestion of water during bathing , eating contaminated food , and interpersonal contact {Briscoe , 1984} ....
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References
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Book•
06 Mar 2012
TL;DR: It would occupy a long time to give an account of the progress of cholera over different parts of the world, with the devastation it has caused in some places, whilst it has passed lightly over others, or left them untouched; and unless this account could be accompanied with a description of the physical condition of the places, and the habits of the people, which I am unable to give, it would be of little use.
Abstract: It would occupy a long time to give an account of the progress of cholera over different parts of the world, with the devastation it has caused in some places, whilst it has passed lightly over others, or left them untouched; and unless this account could be accompanied with a description of the physical condition of the places, and the habits of the people, which I am unable to give, it would be of little use. There are certain circumstances, however, connected with the progress of cholera, which may be stated in a general way. It travels along the great tracks of human intercourse, never going faster than people travel, and generally much more slowly. In extending to a fresh island or continent, it always appears first at a sea-port. It never attacks the crews of ships going from a country free from cholera to one where the disease is prevailing, till they have entered a port, or had intercourse with the shore. Its exact progress from town to town cannot always be traced; but it has never appeared except where there has been ample opportunity for it to be conveyed by human intercourse. There are also innumerable instances which prove the communication of cholera, by individual cases of the disease, in the most convincing manner. Instances such as the following seem free from every source of fallacy. I called lately to inquire respecting the death of Mrs. Gore, the wife of a labourer, from cholera, at New Leigham Road, Streatham. I found that a son of deceased had been living and working at Chelsea. He came home ill with a bowel complaint, of which he died in a day or two. His death took place on August 18th. His mother, who attended on him, was taken ill on the next day, and died the day following (August 20th). There were no other deaths from cholera registered in any of the metropolitan districts, down to the 26th August, within two or three miles of the above place; the nearest being
1,203 citations
TL;DR: The spectrum of illness and the immunologic response produced by cholera in volunteers were studied and Titers of vibriocidal antibody rose after diarrhea, peaked the second week after challenge, and rapidly fell during the next four weeks.
Abstract: The spectrum of illness and the immunologic response produced by cholera in volunteers were studied. The strains of Vibrio cholerae used were classical Inaba 569B and classical Ogawa 395. An oral dose of 108 organisms in buffered saline was required to induce the diarrhea of cholera. When given with live organisms, NaHCO3 lowered the infecting dose from 108 to 104 organisms. Clinical manifestations of infection varied from culturally positive formed stools to "rice water" diarrhea. Severe diarrhea did not have an explosive onset but rather progressively increased in volume during a 24-hr period. In 45% of cases the stool was positive for V. cholerae before the onset of diarrhea. Titers of vibriocidal antibody rose after diarrhea, peaked the second week after challenge, and rapidly fell during the next four weeks.
317 citations
Journal Article•
TL;DR: A preliminary attempt to validate this model using published data on sanitation level, life expectancy, and adult literacy rates, for 65 developing countries appears to provide preliminary support for the threshold saturation theory but further empirical validation is required before a quantitative predictive model can be developed.
Abstract: A general theory on the relationship between water supply and sanitation investments and health, the threshold-saturation theory, is proposed. The theory takes into consideration three variables: health status, socioeconomic status, and sanitation level, and attempts to encompass, for the first time in one general theoretical framework, numerous conflicting empirical findings. The two-tiered S-shaped logistic form of the relationship that is proposed assumes that at the lower end of the socioeconomic spectrum there is a threshold below which investments in community water supplies and/or excreta disposal facilities alone result in little detectable improvement in health status. Similarly, at the higher end of the socioeconomic scale, it is suggested that a point of saturation is reached beyond which further significant health benefits cannot be obtained by investments in conventional community sanitation facilities.
A preliminary attempt to validate this model using published data on sanitation level (defined as access to water supply), life expectancy, and adult literacy rates, for 65 developing countries, appears to provide preliminary support for the threshold saturation theory but further empirical validation is required before a quantitative predictive model can be developed.
83 citations
Journal Article•
TL;DR: Results show that cholera transmission was via contaminated surface water, particularly water taken into households for cooking or drinking, and the frequency of exposure appeared to be a major determinant of the infection rate.
Abstract: The apparent failure of handpump tubewells to reduce the incidence of cholera among users in the flooded rural area of Bangladesh has stimulated interest in defining precisely the means of Vibrio cholerae transmission during localized outbreaks. Cholera-infected neighbourhoods were placed under intensive microbiological surveillance to pinpoint contaminated sources and subsequent infections. The results show that cholera transmission was via contaminated surface water, particularly water taken into households for cooking or drinking. Infections resulted from a daily dose not exceeding 105 organisms and the frequency of exposure appeared to be a major determinant of the infection rate. The importance of these data in environmental interventions and particularly in the provision of tubewells is discussed.
70 citations
"Intervention studies and the defini..." refers background in this paper
...This example is of particular interest because, through a remarkable recent microbiological-cum-epidemiologic study in Matlab (11), direct microbiologic data are available on the frequency with which V....
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...However, the microbiologic data (11) and our model indicate that improving the quality of drinking water did effect a major reduction in exposure to V....
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TL;DR: Luecke and McGinn as mentioned in this paper showed that many "no significant effect" findings may be artifacts of statistical techniques used to analyze cross-sectional survey data, and compared the statistics thus yielded with their knowledge of the causal relationships programmed into the data.
Abstract: Many studies have purported to demonstrate that schooling has little independent impact on achievement and that administrators can do little to boost students' test scores. Daniel F. Luecke and Noel F. McGinn question such results and use variations of a computer simulation model to generate data sets similar to those collected by educational researchers. They subject the data generated to several kinds of aggregation procedures and regression analysis, and compare the statistics thus yielded with their knowledge of the causal relationships programmed into the data. They conclude that many "no significant effect" findings may be artifacts of statistical techniques used to analyze cross-sectional survey data.
30 citations