Global disease mapping identifies 100 million people living at risk of blindness from trachoma

February 11, 2016

Largest infectious disease survey ever undertaken shows where the eye disease trachoma is most prevalent worldwide

One person examined every 40 seconds in 29 countries during the three-year project

Data collected on Android smartphones by 550 mapping teams 

A ground breaking three-year disease-mapping project has shown that 100 million 1 people are at risk of blindness from trachoma.

The Global Trachoma Mapping Project (GTMP), launched in December 2012 and completed in January 2016 2 saw surveyors collect and transmit data from 2.6 million people in 29 3 countries using Android smartphones. On average one person was examined every 40 seconds during the three-year project 4.

The £10.6 million project funded by the UK government’s Department for International Development (DFID), with additional funding from USAID, was led by Sightsavers in collaboration with 30 ministries of health who provided staff, technical support, supervision and vehicles. In total over 60 5 partners worked together across the world, representing a combined effort of an estimated 2,500 people globally. 

The GTMP is the largest infectious disease survey ever undertaken, helping to pinpoint accurately the world’s trachoma endemic areas. The sample of people surveyed during the project represents a global population of 224 6 million people.

The findings of the mapping include trachoma prevalence statistics for 29 countries at risk 7 including Ethiopia, a high burden country where over 50 million people are living in endemic areas.

Thanks to the android technology, the GTMP has been able to capture and record on the  Trachoma Atlas database more districts in three years than had been ever previously been recorded.  The project mapped in areas where no data previously existed because of remoteness, insecurity, insufficient funding, or competing public health priorities.

Having a complete map of the disease’s prevalence means that ministries of health in endemic countries have the evidence base to focus health strategies to tackle the neglected tropical disease with WHO-approved interventions of surgery, antibiotics (through mass drug administration), face-cleanliness and environmental improvements (like sanitation). Ministries of health are now more equipped with accurate information to tackle this disease.

During the last three years, more than 550 teams of trained surveyors, including ophthalmic nurses and other government eye health care workers, have visited millions of people in sample households in the most remote locations of 29 countries, including Chad, Eritrea, Pakistan, Papua New Guinea, Solomon Islands, Colombia and Yemen.

The teams carried out eye examinations and used mobile phones to record their findings, which were then sent to a data centre in Atlanta, USA. There, the information was cleaned and analysed before being sent to local governments for review, approval and use.

Ethiopia has the world’s highest trachoma prevalence, with an estimated 50 million people living in endemic areas. Yabeiywok Sema, who is 60 years old and lives with her husband and grandchildren, was diagnosed with trichiasis by the team of mappers who visited her house. “I had constant pain in my eye and could see less and less which made farming, my main source of income, difficult,” she says. “I didn’t visit the health clinic because I didn’t realise how serious the infection was or that free surgery was available. At times the pain was very bad and I would rub my eyes to try to make it stop.” Yabeiywok was referred to a local health clinic and had surgery one week later to stop her eyesight from deteriorating further.

Trachoma is responsible for three per cent of the world’s blindness. It is caused by the bacterium Chlamydia trachomatis, and is thought to be spread through personal contact (hands, clothing) and by flies that have been in contact with discharge from the eyes or nose of an infected person. After repeated infection it can develop into trichiasis – where the eyelids turn in and the lashes scrape the eyeball, causing great pain and leading to permanent blindness.

Funded by DFID and co-funded by USAID, GTMP was led by Sightsavers. This ground-breaking collaboration was a partnership of 30 ministries of health, the London School of Hygiene & Tropical Medicine, the International Trachoma Initiative, the World Health Organization and over 20 not for profit eye health organisations, most of which are members of the International Coalition for Trachoma Control.   

GTMP epidemiologists and partners helped to strengthen public health systems by training eye health workers in trachoma survey methodology; analysis and data management; and, where applicable will also be supporting the publication of trachoma and WASH survey findings in peer reviewed journals.

Dr Caroline Harper, CEO of Sightsavers, said: “The biggest infectious disease mapping exercise in history, ‘The Global Trachoma Mapping Project’ has been completed within agreed timescales and budget.    Funded by the UK government, in partnership with the US and WHO, this creates a lasting platform which will underpin the drive to eliminate blinding trachoma, and will also contribute to efforts to eliminate other neglected tropical diseases.   It demonstrates how critical accurate data is in the battle to eliminate diseases, and has been a tremendous exercise in collaboration and the use of mobile technology”.                                                         

For further press information, case studies, or interviews, please contact Faith Mall, Senior Media & PR Officer, on 01444 446637                                            

Notes to Editors-------------------

About Sightsavers

Sightsavers is a registered UK charity (Registered charity numbers 207544 and SC038110) that works in more than 30 developing countries to prevent blindness, restore sight and advocate for social inclusion and equal rights for people who are blind and visually impaired.

About the Global Trachoma Mapping Project (GTMP)

  1. GTMP data and systems identified 100 million people globally who live in areas in which the TF (trachoma follicular) prevalence in children is ≥5%. This equates to 45% of the global population surveyed by GTMP.
  2. DFID (Department for International Development) funded GTMP baseline mapping began on December 17th 2012 in Oromia, Ethiopia and final DFID funded GTMP baseline mapping ended on 11th January 2016 in Afar, Ethiopia. (Work was not continuous in Ethiopia. Some projects in Ethiopia were put on hold because of security concerns and inaccessibility – e.g. collapsed bridge). The GTMP grant began in July 2012 and will end in April 2016.
  3. Countries where GTMP methods were used to support baseline mapping include: Benin, Cambodia, Chad, Colombia, Cote d' Ivoire, Democratic Republic of Congo, Egypt, Eritrea, Ethiopia, Fiji, Guinea, Kiribati, Laos, Malawi, Mexico, Mozambique, Pakistan, Papua New Guinea, Nigeria, Republic of Congo, Senegal, Solomon Islands, Sudan, Tanzania, Uganda, Vanuatu, Zambia, Zanzibar, Zimbabwe and Yemen.  The total number of health districts mapped during the timeframe of the Global Trachoma Mapping Project was 1,627.  95% (1,546) of these districts were mapped with GTMP standardised methodologies.
  4. 24 organisations: AMREF, Barraqua Institue, BICO, Brien Holden Institute, The Carter Center, College of Ophthalmology & Allied Vision Sciences, Fred Hollows Foundation, FHI 360, Helen Keller International, International Coalition for Trachoma Control, International Trachoma Initiative (The Task Force for Global Health), Johns Hopkins University, Kilimanjaro Centre for Community Ophthalmology, Light for the World (Austria), Light for the World (Netherlands), London School of Hygiene & Tropical Medicine, Magrabi Foundation, Mitosath, ORBIS, Organisation for the Prevention of Blindness (OPC), Organizacion Panamericana de la Salud (PAHO), RTI, Sightsavers and the World Health Organization. 7 Ethiopian Regional Health Bureaus worked on specific projects including: Afar, Beneshangul Gumuz, Gambella, Oromia, Somali, Southern Nations Nationalities and Peoples’ Region and Tigray Regional Health Bureaus. 30 ministries of health include: Benin, Cambodia, Chad, Colombia, Cote d' Ivoire, Democratic Republic of Congo, Egypt, Eritrea, Ethiopia, Fiji, Guinea, Kiribati, Laos, Malawi, Mexico, Mozambique, Pakistan, Papua New Guinea, Nigeria, Zanzibar, Zimbabwe and Yemen. (In addition ministries of health in Cameroon and Nepal conducted baseline mapping projects during the life of GTMP without the use of GTMP methods.) 2 funders include: DFID and USAID
  5. Based on weighted sample: in each village chosen for mapping, the team randomly selected 30 neighbouring households, and examined every inhabitant except for children under a year old.

About the Department for International Development (DFID)

We lead the UK government’s work to end extreme poverty.  Find out more at


USAID is the lead U.S. Government agency that works to end extreme global poverty and enable resilient, democratic societies to realize their potential. Find out more at For more information on USAID support for trachoma and other NTDs, go to

USAID from the American People   RTI International