Assessing the burden of trachoma
The proportion of individuals showing clinical signs of trachoma (prevalence) amongst specific age groups in a district remains the key indicator for guiding trachoma control programs.
Population-based prevalence surveys (PBPS) give a representative estimate of the population at risk within a district, usually using a cluster randomized design. Other survey methodologies, such as the trachoma rapid assessment (TRA), preferentially sample the most vulnerable individuals from within communities at the highest risk. Such survey designs can provide information of where trachoma is found, but cannot be used to calculate unbiased estimates of prevalence.
How is targeting done
Control decisions and geographical targeting of SAFE components are currently made at the district level. WHO recommend using the prevalence of TF in children between 1-9 years and TT in adults aged 15 and over for deciding where to implement different components of the SAFE strategy. Detailed mapping of trachoma within countries will also be important to assess the degree of overlap with other NTDs and planning for integrated control strategies.