Urban slum DSS is a longitudinal demographic surveillance system in urban areas. Similar to DSS in other settings, the primary objective of urban slum DSS is to collect and analyze demographic and health outcomes from uniquely identified subjects in the DSA through regular repeated visits. In terms of challenges and constraints, urban slum DSS also faces common challenges and constraints to DSS in other settings such as lack of funding.

Urban slum DSS has some unique features. One typical feature of an urban slum DSS is the large and frequent movement of people with in and out of the demographic surveillance area (DSA). The DSA usually receives a high influx of people of whom some stay longer in the DSA before they move out again and some leave the DSA after a short stay. Returning back of ex-DSS members to the DSA is also common in urban slum DSS. Such circular movement of people affects allocation of unique ID to subjects. The success of a DSS will depend on the complete coverage of core events, the correctness of all the information relating to them, and the achievement of assigning unique ID for DSS subjects. In other words, assigning unique IDs for individuals who ever lived in the DSA and also a unique ID for ever registered household in the DSA is crucial to monitoring changes over time. However, the huge and frequent movement that are common phenomenon in urban slum DSS pose a number of unique challenges to urban slum DSS. These include a) a higher risk of failing to capture all movement and other core demographic events; and b) a higher risk of assigning more than one unique ID to ever- resident individuals and ever- formed households in the DSA.

In its urban slum DSS, the African Population and Health Research Center (APHRC) registers all individuals in the DSA and follow up subsequently over time to monitor and document changes in various events, such as: pregnancies, deaths, in- migrations, births, illness episodes, work spells, health seeking behavior, etc. These events will be recorded only for individuals who qualify as ‘residents’ of the DSA. A person is considered a member of the DSS if he/she has lived in the DSA for at least 90 days. This means that no inquiry will be made about events that occurred before the date when the household was first registered in the DSS. The only exception is the registration of pregnancies and pregnancy outcomes, which are registered irrespective of when they were conceived. If a DSS member moves out of a DSS household for at least three months (90 days), he/she will be considered an out- migrant. New people who will move into a household within the DSA will be registered as in-migrants after they spend at least three months (90 days) in that household.  Between the times such people move into the DSS household and when they get registered as in-migrants, they will be considered visitors. Births or deaths to visitors are not DSS events. People who move within the same DSA will be considered as having changed residence, and such movements will be registered through change of residence forms. Movements of people into and out-of the DSA will be registered through migration forms.

To keep track of changes that might be observed overtime, the DSS must ensure assigning unique ID to individuals and households in the DSS. In urban slum DSS where movement is high there is a high risk of assigning more than one ID to subjects. To minimize assigning a duplicate ID when using movement forms (for those who changed residence within the DSA or returning in-migrants) adequate mechanisms should be in place to verify whether the subject had ever been given an ID in the DSA or to trace the ID if one had ever been given. The ideal thing is to use the ID that was given earlier if a person was found to have moved into a different dwelling unit or who is a return migrant to the DSA. This suggests a need to verify the following two issues: a) if the person has ever lived in the DSA; and b) if the person in-migrating did the movement with the household that is newly formed or not. The first will help in making decision whether or not a new ID should be assigned to the person whereas the second point relates to whether or not a new ID for the household should be given. To facilitate searching for existing IDs for DSA-ever- lived individuals, some matching questions need to be included. APHRC makes some effort to handle these challenges. First it includes some questions that help in establishing the fact that whether or not the person moved into different location within the DSA or came to the DSA as a return in- migrant. Second, it equips its field offices with computers so that searching/verifying would be efficient. The following questions are included to facilitate search for existing ID in the data base:

Matching questions