Survey data maps can only be as reliable as the data they display. Whist strict inclusion and exclusion criteria are applied, users should bear a few things in mind:
- Area-level averages: for much of the world, in particular Asia and the Middle East, survey data is only reported at a district or provincial level. Whilst work is ongoing to locate the co-ordanates of these surveys, in such instances area-level averages are currently shown. However, included surveys may have been conducted in single schools or communities and as such may not be representative of the whole district/province population.
- Changes over time: country data may have reflect surveys conducted over a wide period of time. These maps cannot reflect temporal changes in prevalence, which may be due to changes in socio-economic conditions, improvements in hygiene and sanitation, or the implemenation of school-based and mass treatment campaigns.