Prácticas inclusivas y caracterización del alumno

Other estimates of reductions in diarrhoea risk are presented by Prüss et al.[2002] andWaddington et al.[2009], who consider re- ductions in a full WSS setting284

. As improvements in water supply

284

A. Prüss, D. Kay, L. Fewtrell, and J. Bartram. Estimating the global burden of disease from water, sanita- tion, and hygiene at the global level.

Environmental Health Perspectives,110 (5):537–542,2002; and H. Waddington, B. Snilstveit, H. White, and L. Fewtrell.

Water, sanitation and hygiene interven- tions to combat childhood diarrhoea in developing countries. 3ie, New Delhi, 2009

can be confounded by a household’s sanitation situation, their es- timates adjust for a household’s sanitation situation. They also consider whether households practice POU treatment of water. These estimates are based on six general scenarios (with further breakdowns of two of these scenarios) proposed byPrüss et al. [2002] for classifying WSS based on increasing level of risk of di- arrhoeal diseases. These scenarios can be used to characterise the WSS situation for a location and are presented in Box11. The scope of scenarios considered ranges from an ideal scenario where there is no diarrhoea morbidity or mortality due to inadequate WASH to a scenario where households do not have access to improved water or improved sanitation and, consequently, are at highest risk.

Scenario Description

I: No transmission of diarrhoea through WASH

II: Regulated water supply (typically piped), full sanitation coverage, partial treatment of sewage

III

a: Improved water supply, improved sanitation, POU water treatment

b: Improved water supply, improved sanitation, improved hygiene

c: Further improved water supply (typically piped), improved sanitation IV: Improved water supply, improved sanitation

V

a: Unimproved water supply, improved sanitation

b: Improved water supply, unimproved sanitation VI: Unimproved water supply, unimproved sanitation

Box11_{: Classifications for water} supply and sanitation considered by Prüss et al.[2002].

Neither of the first two scenarios considered byPrüss et al. [2002] typically apply to developing countries, but the remaining scenarios describe the situation for households in Ribáuè in2012 and2014. Table42presents the relative prevalence of the various WSS scenarios in Ribáuè in both September2012and November 2014, and, in line with previously discussed changes in Ribáuè due to NAMWASH, these show a significant improvement in terms of WSS and anticipated lower risk of diarrhoeal diseases.

IIIa IIIc IV Va Vb VI September2012 0.79% 0.40% 3.17% 2.38% 39.68% 53.57% (0.00%,1.89%) (0.00%,1.17%) (1.01%,5.34%) (0.50%,4.26%) (33.64%,45.72%) (47.41%,59.73%) November2014 10_.86_% 2_.66_% 18_.24_% 13_.11_% 31_.97_% 23_.16_% (7.02%,14.70%) (0.68%,4.65%) (13.47%,23.01%) (8.95%,17.28%) (26.21%,37.73%) (17.95%,28.36%) Piped Water2014 0.79% 5.95% 93.25% (0_.00_%,1_.89_{%) (}3_.03_%,8_.87_{%) (}90_.16_%,96_.35_%)

Table42_{: Estimated distribution of} water and sanitation scenarios in the town of Ribáuè in September2012 and November2014. We also present a theoretical estimate (“Piped Water 2014”) of what would be anticipated in 2014if piped water was supplied to all households and there was no change in the way of sanitation.

As totals for Ribáuè from November2014only reflect the short- term impacts of introduction of piped water while also reflecting the significant sanitation interventions carried out in Ribáuè, we consider the impact that would have been expected from2012to 2014if piped water had been delivered to all homes and no san- itation interventions took place, and these are shown in the last row (“Piped Water2014”) of Table41. These totals reflect a shift of households in Scenario VI to Scenario Vband households in Scenarios Vaand IV to Scenario III. Understanding these shifts be- tween scenarios allows for an understanding of the full scope of health benefits that could be anticipated from piped water to the home, corresponding to the totals costs presented in the previous chapter. These will help shape the estimation of economic benefits related to those costs.

Based on the scenarios presented byPrüss et al.[2002], estimates of reductions in risk fromPrüss et al.[2002],285and subsequent up-

285

These estimates take into consid- eration a wide swathe of studies that include examinations of water inter- ventions (including those byEsrey and Habicht[1985] andEsrey et al.[1991]), sanitation interventions, and hygiene interventions.

dates byWaddington et al.[2009] to incorporate more recent stud- ies,Hutton[2012] presents the relative risks of diarrhoea shown

e s t i m at i n g t h e b e n e f i t s o f p i p e d wat e r t o h o u s e h o l d s 125

in Table43, which consider Scenario VI as reflecting baseline risk and subsequent relative risks representing reductions in risk based on progressive improvements in WSS. Note that the estimate for the relative risk corresponding to Scenario III is based on the rela- tive risks presented byPrüss et al.[2002] and was not included by Hutton[2012]286. AlthoughPrüss et al.[2002] report several stud-

286

This is presumably because that study only considered what would be required to meet the water and sanitation targets specified by the Millennium Development Goal, and Scenario III consisted of improvements (piped water, hygiene improvements, POU water treatment) that exceeded what would be required to meet these targets.

ies that could be used to estimate relative risks corresponding to to Scenarios IIIaand IIIb, they could not identify any studies that would allow for direct estimation of Scenario IIIc, and they instead uniformly apply a relative risk to all sub-components (a-c) of Sce- nario III, producing the relative risk shown.

Scenario III IV Va Vb VI

Relative Risk 0.41 0.61 0.64 0.82 1.0

Table43: Relative risks for diarrhoea corresponding to the scenarios pre- sented in Box11.

The relative risks presented in Table43can be used calculate percentage reductions in risk, so, for instance, a transition from sce- nario VI to Scenario IV should correspond to a39% reduction in diarrhoea morbidity and mortality, while a transition from Scenario Vbto Scenario IV should correspond to a roughly25% reduction. If we know diarrhoea mortality and morbidity, we can estimate reduc- tions based on transitions between scenarios due to introduction of piped water to the home.

Estimates of diarrhoea incidence for children under the age of five and all others are presented in Table17. As already noted, we do not observe a significant difference between incidence recorded in2012and2014for the town of Ribáuè, and, in the interest of pro- ducing a conservative estimate for expected reduction in diarrhoea incidence, we use the lower of the two estimates of incidence for each age category, meaning that we consider incidence to be as shown in Table44. Note that, rather than consider all individuals over the age of4as one group, we further break this category down according to typical school age and adult years, as done byHut- ton[2012]. For the town of Ribáuè in2014, this would produce an estimated20,612cases of diarrhoea per year. Calculations used to produce these estimates are presented in Appendix A.

<5years 5-14years ≥15years

Incidence 8.59% (5.79%,11.40%) 1.53% (0.32%,2.75%) 0.78% (0.10%,1.47%)

Cases 12,389.61 4,458.97 3,763.28

Table44_{: Estimated incidence of diar-} rhoea and number of cases annually by age for the town of Ribáuè.

Due to the absence of town-, district-, or provincial-level esti- mates of mortality due to diarrhoeal diseases, we rely on country- level mortality (due to all causes) reported byWorld Bank[2015] and reports of death due to diarrhoeal diseases reported byWorld Health Organization Global Health Observatory[2015] for2013287.

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World Bank. World Development Indicators, Mozambique,2015. URL http://data.worldbank.org/country/ mozambique/#cp_wdi; and World Health Organization Global Health Observatory.Mozambique: WHO statis- tical profile. World Health Organization, Geneva,2015. URLhttp://www.who. int/gho/countries/moz.pdf?ua=1 These are used to estimate the age-specific probabilities of death

due to diarrhoeal diseases, as shown in Table45, allowing us to es- timate total deaths due to diarrhoea for the town of Ribáuè in2014.

Appendix A provides information on the data and calculations used to produce these estimates.

<5years 5-14years ≥15years Probability of Death 0.16% 0.03% 0.03%

Deaths 8.92 3.88 6.41

Table45_{: Estimated probability of} death due to diarrhoea and number of deaths annually by age for the town of Ribáuè.

Note that some have taken the approach of using case fatality rates to estimate mortality by calculating mortality as a percentage of cases of diarrhoea. For instance,Prüss et al.[2002] used case fa- tality rates derived fromMurray and Lopez[1996] and then applied this proportionally to all instances of diarrhoea288

. This approach 288

C.J.L. Murray and A.D. Lopez.

Global Health Statistics. Harvard School of Public Health, World Health Orga- nization, and World Bank, Cambridge, 1996

can be shown to be equivalent to the approach we have taken when the data used are estimates produced using case fatality rates289

.

289

In fact, it is likely thatWorld Bank [2015_{] reports are actually estimates} based on case fatality rates. We used World Health Organization Global Health Observatory[2015_{] reports for} over all mortality due to diarrhoea, however, and these differed substan- tially from projections fromWorld Bank[2015]. Given that theWorld Health Organization Global Health Observatory[2015] total was sub- stantially lower, we would expect our estimates to be more conservative than estimates relying on published case fatality rates (or estimates produced using them).

Now, it is important to recall thatCairncross and Valdmanis[2006] report not only a reduction in incidence of diarrhoea with water in close proximity to the home but also a reduction in severity, sug- gesting that case fatality rates are likely to be associated with the water situation of a household. To the best of our knowledge, no one has yet investigated this relationship, so the nature of changes in fatality rates due to improved WSS situations is not known. Con- sequently, in line with other studies, we do not consider differential case fatality rates based on WSS situation of the household.

If we assume that diarrhoea morbidity and mortality for a given age rage are uniformly distributed across households290

, then a

290

In reality, we would expect mor- bidity and mortality to be higher for scenarios corresponding to worse WSS situations.

change from the situation in terms of WSS scenarios observed in 2012to the situation that would be expected if only piped water was introduced to all households (as shown in Table42) produces an estimated11.54% reduction reduction in morbidity and mortal- ity. This would lead to the total reduction in cases of diarrhoea and deaths that could be expected in a given year for Ribáuè shown in Table46.

<5years 5-14years ≥15years Morbidity:

Cases (September2012) 11,947.20 4,299.78 3,628.59 Cases (Piped Water2014) 10,569.57 3,803.61 3,209.87

Reduction 1,378.63 496.17 418.72

Mortality:

Deaths (September2012) 8.60 3.74 6.18 Deaths (Piped Water2014) 7.61 3.31 5.47

Reduction 0.99 0.43 0.71

Table46: Estimated diarrhoea morbid- ity and mortality for Ribáuè for2014 and anticipated reduction as based on a WSS situation in line with what was observed for2012and as estimated based on transitions due to an inter- vention consisting strictly of piped water to the home. These correspond to the distributions shown in Table43.

The reduction of slightly over10% appears small when consider- ing thatCairncross and Valdmanis[2006],Esrey and Habicht[1985], andEsrey et al.[1991] cited reductions in excess of50% due to in- troduction of piped water to the home. We note that the seemingly small reduction in diarrhoea morbidity and mortality can partially

e s t i m at i n g t h e b e n e f i t s o f p i p e d wat e r t o h o u s e h o l d s 127

be attributed to a large percentage of households corresponding to Scenario Vbnot seeing a shift to an improved scenario due to the fact that they had unimproved sanitation facilities. If there was a greater use of improved sanitation facilities prior to NAMWASH, percentage reductions would be more substantial. However, it would also be expected that the baseline incidence would have been lower than what we observed, so, even though the percentage reduction would be greater, the reduction in terms of raw numbers would still be less. At the same time, our estimated reduction is likely to be conservative, given that Scenario Vbis meant to rep- resent a situation where households would likely have access to boreholes and possibly standpipes but not yard taps or household connections. A situation where water is piped to the home would likely lead to a more significant reduction, but no estimates of the change in relative risk corresponding to such a situation are avail- able.