An estimated 129.4 million people live in areas of Africa where blinding trachoma is confirmed to occur, according to a paper publishing August 8 in PLOS Neglected Tropical Diseases. The distribution of the disease varies greatly across the continent, with clinical signs most common in the Sahel area of West Africa and the savannah areas of East and Central Africa.

Trachoma is the leading infectious cause of blindness worldwide. In 1998, the World Health Organization (WHO) established the Alliance for Global Elimination of Trachoma by the year 2020 (GET2020). The strategy employed to eliminate trachoma is based on a combination of interventions known as SAFE: Surgery to correct trichiasis; Antibiotics to treat infection by the bacterium that causes trachoma, Chlamydia trachomatis; Facial cleanliness, and Environmental improvement to reduce transmission. Researchers, donors and implementers have long acknowledged the importance of mapping the distribution of trachoma to help target intervention strategies to areas in greatest need.

Recognizing a lack of epidemiological data on the geographical distribution of this neglected tropical disease (NTD), the Global Atlas of Trachoma (GAT) was jointly launched in 2011 by the International Trachoma Initiative, London School of Hygiene & Tropical Medicine and The Carter Center to provide standardized and accessible maps for all partners. Epidemiological data on the global burden of trachoma since 1980 were identified through direct contact with trachoma control programmes or structured searches of published and unpublished literature. The project works closely with national programmes to ensure that maps are rapidly updated and meet programmatic requirements. Prevalence data on active trachoma are available in 29 of the 33 countries in Africa classified as endemic for trachoma, and estimates reflect data available as of September 2012.

"Our analysis provides a detailed description of the burden of trachoma across Africa, which suggests that as many as 230 million individuals live in areas that are either confirmed or suspected to be endemic for trachoma. As survey activities are scaled up in areas where data are lacking, estimates will continue to be refined to reflect our growing knowledge," says Jennifer Smith, of the London School of Hygiene & Tropical Medicine.

Well established control programmes in several African countries are likely to have had an impact on the burden of trachoma in the last decade, with successes in control activities documented in Burkina Faso, Mali, Mauritania and Ethiopia. Furthermore, The Gambia, Ghana and Morocco have now reported achieving trachoma elimination targets and the disease is no longer believed to be a public health concern in these countries.

"The findings revealed by this rapidly increasing pool of data are important because they assist in the assessment of the distribution and magnitude of the problem, which is crucial for the planning and implementation of preventive, curative and surgical services to the people most in need," says Prof. KH Martin Kollmann, chair of the International Coalition for Trachoma Control (ICTC). "Providing a commonly accepted, permanently updated and readily available source of data, the GAT not only underpins a sense of urgency but also helps to prioritize and coordinate activities between national programmes, donors and implementing partners such as represented at the ICTC."

The work also highlights where future mapping is required. Further to survey data for inclusion in the GAT, the UK Department for International Development recently funded the Global Trachoma Mapping Project (GTMP), which aims to complete mapping of trachoma across more than 30 countries by April 2015. GTMP is an essential step towards trachoma elimination by the target date of 2020, and data collected as part of the GTMP are included in the GAT in real-time using handheld GPS technology.

With this data in hand, national control programmes and NGO's can now better prioritize where treatments are needed most and scale-up their interventions accordingly," says Danny Haddad, Director of the International Trachoma Initiative.

The GAT and the GTMP build on ongoing efforts to map the global burden of NTDs. The Global Atlas of Helminth Infections provides maps and data on the distribution of worms such as soil-transmitted helminths, schistosomiasis and lymphatic filariasis. The open-access resources serve to guide school-based deworming and mass drug administration programmes.