Page et al. BMC Public Health 2011, 11:389 http://www.biomedcentral.com/1471-2458/11/389 [8,12,13]. The World Health Organization (WHO) developed a generic protocol for the hospital-based sur- veillance of severe diarrhea due to rotavirus in children under 5 years of age to inform decision making prior to vaccine introduction [14]. The recommended first step of this protocol is a survey among caretakers of children under 5 years of age to establish their hospital-use pat- tern in case of diarrhea. A first field-test of the survey protocol in Ghana showed that a hospital-based surveil- lance of rotavirus would miss the vast majority of chil- dren with severe diarrhea [15], emphasizing the need for investigating local specificities before implementing a surveillance system. The organization of the health system in Niger is based on several international initiatives launched in 1995-1996 [16]. This period was marked by the creation of health districts for decentralization of care, the gra- dual introduction of the Integrated Management of Childhood Illness (IMCI) algorithms [17] in all districts, and the implementation of cost recovery following the Bamako Initiative [18]. Despite these efforts, the most recent national Demographic and Health Survey (DHS) in Niger in 2006 showed that only 17% of caretakers of children under 5 years of age had sought advice or treatment for childhood diarrhea [19]. With the aim of reducing child mortality in line with the UN Millennium Development Goals, free care for children under 5 years of age was introduced in April 2007. The health system in Niger is pyramidal based on health structures with increasing levels of service: health posts (cases de santé), health centers (centres de santé intégrés), district and regional hospitals [20]. Health posts provide basic care and preventive services and are staffed mainly by com- munity health workers aided by community representa- tives. Health centers are staffed by nurses and ensure the provision of all services not requiring hospitalization. Diarrhea with severe dehydration is the only severe con- dition that does not automatically lead to referral to a hospital. In the absence of other severity signs, diarrhea with severe dehydration is managed by injection of intravenous fluids at the health center level. The objective of this study was to determine the pro- portion of children under 5 years of age suffering from severe diarrhea, who were treated in the health care sys- tem of Maradi region, Niger. This was an initial step to determine the suitable sites to implement a rotavirus and diarrheal disease surveillance system in order to provide essential information for guidance on vaccine introduction. Page 2 of 7 million inhabitants in 2009 (Recensement general de la Population, 2001, Institut National de la Statistique). The survey took place in four health districts of the region: the city of Maradi, and rural districts of Madar- ounfa, Aguié and Guidan Roumdji, with a total popula- tion of approximately 1.4 million. The city of Maradi is the third largest in Niger and its economic capital. The public health system coverage reported by the Ministry of Health - i.e. the proportion of the population with access to a health structure, including health post, within a distance of less than 5 km - is 100% in the city of Maradi. Aguié, Madarounfa and Guidan Roumdji are large rural districts covering areas of 2800, 4700, 3500 km2, respectively. In 2009, the average number of public health structures in 100 km2 was 1.5 (Madarounfa) to 2.1 (Aguié and Guidan Roumdji) and the public health system coverage was 85%, 83% and 94% in Aguié, Madarounfa and Guidan Roumdji, respectively. Study population All children aged 0 to 59 months resident in the survey districts at the time of the study were eligible for inclu- sion. The sample was obtained using stratified cluster sampling with each of the three above-mentioned dis- tricts and the city of Maradi considered as separate strata. For the sample size calculation, we assumed an alpha error of 0.05, precision of 5%, a design effect of 2 and expected prevalence of severe diarrhea of 30%. Con- sidering these assumptions and including 10% of missing or incomplete data, the minimum sample size was 708 children in each stratum. To obtain the desired sample size we used 35 clusters of 21 children in each stratum. Clusters were allocated within the four strata propor- tionally to the population of each village, based on the most recent population census in 2001 adjusted by an annual growth rate (Recensement general de la Popula- tion, 2001, Institut National de la Statistique). In the city of Maradi, spatial sampling using a super-imposed grid was used to select the starting point. In the rural districts, we followed the WHO EPI methodology [21]. Households were defined as individuals sleeping regu- larly under the same roof and sharing meals. As poly- gamy is common in this region, a wife and her children were each considered a unique household. If more than one household was present in a home, one household was chosen randomly with the aid of a random number table. Similarly, if more than one child aged 0 to 59 months was eligible for inclusion in the selected house- hold; one child was selected at random. Methods Study Site The region of Maradi is comprised of seven health dis- tricts with a total estimated population of about 3 Data collection All information was elicited by interviews, which were conducted with the mother or caretaker. A recall period of 27 days (April 24th until May 21st) was used. The