A theoretical model is proposed that relates the level of ingestion of diarrhoea-causing pathogens to the frequency of diarrhoea in the community. The implications of this model are that, in poor communities with inadequate water supply and excreta disposal, reducing the level of enteric pathogen ingestion by a given amount will have a greater impact on diarrhoea mortality rates than on morbidity rates, a greater impact on the incidence rate of severe diarrhoea than on that of mild diarrhoea, and a greater impact on diarrhoea caused by pathogens having high infectious doses than on diarrhoea caused by pathogens of a low infectious dose. The impact of water supply and sanitation on diarrhoea, related infections, nutritional status, and mortality is analysed by reviewing 67 studies from 28 countries. The median reductions in diarrhoea morbidity rates are 22% from all studies and 27% from a few better-designed studies. All studies of the impact on total mortality rates show a median reduction of 21%, while the few better-designed studies give a median reduction of 30%. Improvements in water quality have less of an impact than improvements in water availability or excreta disposal.

Interventions for the control of diarrhoeal diseases among young children: improving water supplies and excreta disposal facilities.

L'amelioration de l'eau et de l'hygiene a des impacts benefiques sur la sante, notamment des enfants. Ces impacts dependent du type d'intervention, du degre d'exposition aux germes pathogenes dans la region et de la presence ou non de certains facteurs de risque

Epidemiologic evidence for health benefits from improved water and sanitation in developing countries

Introduction. Climate change projections indicate that droughts will become more intense in the 21 century in some areas of the world. The El Nino Southern Oscillation is associated with drought in some countries, and forecasts can provide advance warning of the increased risk of adverse climate conditions. The most recent available data from EMDAT estimates that over 50 million people globally were affected by drought in 2011. Documentation of the health effects of drought is difficult, given the complexity in assigning a beginning/end and because effects tend to accumulate over time. Most health impacts are indirect because of its link to other mediating circumstances like loss of livelihoods. Methods. The following databases were searched: MEDLINE; CINAHL; Embase; PsychINFO, Cochrane Collection. Key references from extracted papers were hand-searched, and advice from experts was sought for further sources of literature. Inclusion criteria for papers summarised in tables include: explicit link made between drought as exposure and human health outcomes; all study designs/methods; all countries/contexts; any year of publication. Exclusion criteria include: drought meaning shortage unrelated to climate; papers not published in English; studies on dry/arid climates unless drought was noted as an abnormal climatological event. No formal quality evaluation was used on papers meeting inclusion criteria. Results. 87 papers meeting the inclusion criteria are summarised in tables. Additionally, 59 papers not strictly meeting the inclusion criteria are used as supporting text in relevant parts of the results section. Main categories of findings include: nutrition-related effects (including general malnutrition and mortality, micronutrient malnutrition, and anti-nutrient consumption); water-related disease (including E coli, cholera and algal bloom); airborne and dust-related disease (including silo gas exposure and coccidioidomycosis); vector borne disease (including malaria, dengue and West Nile Virus); mental health effects (including distress and other emotional consequences); and other health effects (including wildfire, effects of migration, and damage to infrastructure). Conclusions. The probability of drought-related health impacts varies widely and largely depends upon drought severity, baseline population vulnerability, existing health and sanitation infrastructure, and available resources with which to mitigate impacts as they occur. The socio-economic environment in which drought occurs influences the resilience of the affected population. Forecasting can be used to provide advance warning of the increased risk of adverse climate conditions and can support the disaster risk reduction process. Despite the complexities involved in documentation, research should continue and results should be shared widely in an effort to strengthen drought preparedness and response activities.

Health Effects of Drought: a Systematic Review of the Evidence

Background.New Zealand is in its ninth year of a serogroup B meningococcal disease epidemic with annual rates of up to 16.9 cases per 100 000. The highest incidence is in Maori and Pacific Island children in the Auckland region. We conducted a case-control study to identify potentially modifiable ri

Household crowding a major risk factor for epidemic meningococcal disease in Auckland children.

The incidence of eye infections in a community is generally accepted as an indicator of the adequacy of water supply for their needs. However, discrepancies in the published results from various studies seem to challenge this view. We have reanalysed the published data on trachoma in relation to the most relevant indicators of water accessibility, using prevalence ratios as the single parameter for risk assessment. A definite trend emerges from this review: the incidence of infectious conjunctivitis is not sensitive to differences in water accessibility; on the other hand, a reduction in the risk of trachoma is consistently associated with better access to water. This conclusion may support the efforts of WHO and other multilateral and bilateral agencies to sustain the commitment towards the water supply sector beyond the International Drinking Water Supply and Sanitation Decade.

VolvickRémy Joseph

Papers

Acute water shortage and health problems in haiti