A structured survey was completed for each participating household with information on both household-and individual-level characteristics. All household members were enumerated and an adult proxy was interviewed for children <15 years old or older residents not present at the time of the interview to determine whether any household member met any of the case definitions (mild or severe respiratory, diarrhea, acute febrile and acute neurologic illness) during the prescribed time period. A clinical history was obtained for each illness episode (if more than two episodes of the same illness were reported, the most recent illness episode was used as the reference) along with a history of healthcare treatment seeking. Proxies of household residents who died but met the case definition for one of the illnesses in the relevant time period before death were also administered the illness-specific forms.