Academic journal article Bulletin of the World Health Organization

The Magnitude of the Global Problem of Diarrhoeal Disease: A Ten-Year Update

Academic journal article Bulletin of the World Health Organization

The Magnitude of the Global Problem of Diarrhoeal Disease: A Ten-Year Update

Article excerpt

In order to update global estimates of diarrhoeal morbidity and mortality in developing countries, we carried out a review of articles published from 1980 to the present and calculated median estimates for the incidence of diarrhoea and diarrhoeal mortality among under-5-year-olds. The incidence of diarrhoea obtained (2.6 episodes per child per year) was virtually the same as that estimated by Snyder & Merson in 1982, while the global mortality estimate was lower (3.3 million deaths per year; range, 1.5-5.1 million). The mortality estimate is based on a small number of active surveillance and prospective studies, and thus associated with a large degree of uncertainty, reflecting the weakness of the global database. However, many surveys reporting reductions in mortality in several locations are consistent with a decreased estimate for mortality. More accurate execution of WHO survey methods, including population-based sampling in representative locations, and repeat surveys every 5 years, are needed to monitor the progress of diarrhoeal disease control programmes and trends in diarrhoeal morbidity and mortality over time.

In 1982 Snyder & Merson published their landmark article giving the first estimate of global morbidity and mortality from diarrhoeal disease based on active surveillance data collected from longitudinal studies of children [1]. During the intervening decade, diarrhoeal disease control programmes have been established in many countries, with oral rehydration therapy as the keystone, and new methods have been developed for assessing mortality through verbal autopsies and cross-sectional surveys. Two reviews in the past decade have suggested that diarrhoeal disease mortality may be decreasing worldwide [2, 3]. In addition, an enhanced understanding of the interaction of persistent diarrhoea and malnutrition as causes of mortality has reinforced the need to broaden the scope of intervention programmes beyond treatment based on oral rehydration therapy alone [4].

The present article updates the analysis of Snyder & Merson in the light of new insights into diarrhoeal disease morbidity and mortality. The following basic questions guided the approach: [1] What is the present magnitude of morbidity and mortality from diarrhoeal disease, and has it changed in the past decade? If so, has the change occurred in response to improved treatment programmes? [2] Are the methods currently employed to measure morbidity and mortality sufficiently sensitive to detect changes over time? [3] How should the next decade of diarrhoeal disease control be planned, and what epidemiological methods should be used to monitor its effect?

Methods

The studies included in our analysis were initially identified by a computer search of the scientific and demographic literature published since 1980, using the search categories "diarrhoea and mortality" and "diarrhoea and morbidity". Other references were obtained from citations in these articles and through discussions with experts in the field. The majority of these studies were conducted in the 1980s, although a few [5-7] were carried out in the late 1970s and published in 1980 or later. Snyder & Merson's review covered studies conducted between 1954 and 1979.

Morbidity

For the analysis of diarrhoeal morbidity, we followed the methods used by Snyder & Merson. Estimates of diarrhoea incidence were collected from longitudinal community-based studies of stable populations, in which active surveillance for diarrhoea was conducted by visiting children on a biweekly or more frequent basis for a minimum period of 1 year. If a treatment intervention was part of the study design, the rates for the control area, not the intervention area, were used for the analysis.

We used the same design factors that were employed by Snyder & Merson, including the age group studied, geographical locations, definition of diarrhoea, frequency of surveillance, and size of the study population. …

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