Page et al. BMC Public Health 2011, 11:389 http://www.biomedcentral.com/1471-2458/11/389 length of the questionnaire and the recall period. It is interesting to note that the data parallel an approxi- mately 3.5 × increase in the number of consultations for diarrhea in children under 5 years of age reported from the health centers in Niger between 2006 and 2009 [24]. Abolition of user fees for children under 5 years old in April 2007 may be one of the major reasons for this increase. User fees have been shown to have an impact on patient behavior, and in particular on the delay before consultation and in the most vulnerable groups [25,26]. The proportion of patients having received oral rehy- dration solution shows good compliance with national and international recommendations for the treatment of simple diarrhea [4,27]. However, only half of the cases retrospectively classified as severe received intravenous rehydration therapy. Interestingly, the type of health structure visited did not vary much according to sever- ity, both in the retrospective and hypothetical question- naire, with health centers as the most frequently visited structures, followed by health posts. Referrals were not precisely documented here, but hospitalizations for at least one night were recorded and reported in only 44% of severe cases. As this also includes patients who stayed overnight at a health center, it is an over-estimate of the proportion of severe cases who were admitted to hospi- tal. This, together with the decentralized healthcare organization and recommendations for treatment of severe dehydration at the health centre level, suggests that the majority of children with severe diarrhea would be missed by a hospital-based surveillance system. Data from other African settings also show the limits of hospital-based surveillance. Similar low coverage of hospital-based surveillance was also concluded from a survey in Ghana [15]. In a hospital-based study in Kenya, the reported incidence of rotavirus-associated diarrhea was at least 70% higher in the areas close to the hospital than in the district overall [28]. Relying only on hospital based surveillance may have an impact on the estimated incidence of rotavirus-associated diar- rhea, but also on the characterization of circulating gen- otypes, as well as on the estimation of expected health and economic impacts of vaccination, which are essen- tial indicators to guide vaccine introduction [11,29,30]. The principal limitations of this study are related to its retrospective design. The survey was meant to focus pri- marily on severe diarrhea but retrospective classification of the severity of the disease was made difficult by the subjective assessment of dehydration signs, as shown even among clinicians [31]. Recall bias for diarrhea has been shown to be high after 7 days, with under-report- ing up to 45% after this time [32,33]. Positive behavior (here consultation at a health structure) could have been over-reported, although it was mentioned by Page 6 of 7 surveyors that many caregivers showed the health pass- port of the child to prove the visit at the health struc- ture. Finally, the questionnaire focused on health- seeking behavior of the care provider and was not opti- mal for documenting subsequent referrals within the healthcare system. Some of these limitations could be addressed in the future by slightly modifying the survey methodology. First and most importantly, severity scales such as the Clark or Vesikari scores might be more appropriate to evaluate severity than dehydration signs. These scores are widely used, in particular as the main outcome to assess rotavirus vaccine efficacy [34]. A modified Vesikari score was proposed and validated for use in outpatient settings, which excludes dehydration signs, considered subjective, in favor of objective signs such as number of stools or vomiting or duration of ill- ness [35]. We suggest that this score be adapted and used for retrospective assessment of diarrhea in the future. Other suggested modifications include recording travel time from the house to nearest health care struc- ture, clarifying questions on different steps in health care seeking behavior (first and subsequent visits, refer- rals), and, when possible, asking for the health passport to confirm the visit. Conclusions The results of this survey show an increase in health care seeking behavior in case of diarrhea of children under 5 years of age in the Maradi region since the 2006 DHS survey, suggesting the efficacy of recent health policies for children in Niger. In addition, the data suggest that hospital-based surveillance of severe diarrheal diseases might not be appropriate in this type of decentralized health system. Health centers and posts are the cornerstone of the health system, in particular in rural areas, and should not be overlooked for the estab- lishment of surveillance systems. Acknowledgements and Funding We would like to thank the interviewers and supervisors for their motivation and good work. We are grateful to the children and families, as well as to the communities for their participation in the study. We also thank the staff of Epicentre in Maradi for their support all along the study. The study was funded by Médecins Sans Frontières. Author details 1Epicentre, Paris, France. 2Ministère de la Santé, Niamey, Niger. 3Direction Régionale de la Santé Publique, Maradi, Niger. Authors’ contributions ALP had full access to the data, carried out the data analysis and drafted the manuscript. SH participated in the design of the study, carried out the survey and participated in the data analysis. FJL participated in the design of the study, data analysis and interpretation and review of the paper. AD and MLM participated in the interpretation of the data. RFG participated in the study design, data analysis and interpretation, drafting and review of the manuscript, and obtained funding. All authors read and approved the final manuscript.