The World Health Organization (WHO) estimates that a significant proportion of tuberculosis (TB) patients do not have access to diagnostic testing and treatment. This proportion of undiagnosed patients, which can account for more than half of tuberculosis cases in some parts of the world, contributes significantly to TB-related mortality and spread.

For this reason, WHO recommends that active TB screening activities be carried out in high-risk populations. These populations are traditionally defined as those who have had close contact with a patient with active pulmonary tuberculosis. However, it has been shown in several studies that more than two-thirds of transmissions occur outside this family or professional setting. It is therefore necessary to develop innovative strategies to precisely target very high-risk populations.

Researchers from UCLouvain and KU Leuven have developed an approach to better assist local actors (national programmes, non-governmental organisations, local community organisations). This approach consists in developing maps that accurately predict geographical areas where tuberculosis incidence is highest.

A precise description of the mechanisms behind these maps can be found in:

Data-driven identification of communities with high levels of tuberculosis infection in the Democratic Republic of Congo
Mauro Faccin, Olivier Rusumba, Alfred Ushindi, Mireille Riziki, Tresor Habiragi, Fairouz Boutachkourt & Emmanuel André
Scientific Reports, 12, 3912 (2022)

How are these maps constructed?

Maps are constructed by combining a series of freely available data such as demographic data or the presence of groups known to be at high risk (prisons, mining, …) when these data are available. This first layer is then complemented by a mapping of health centres and tuberculosis notification data for each of these centres.

All tuberculosis cases reported at a health centre are then redistributed to all places in the area covered by the centre.

The analysis applies a coefficient increasing the probability of tuberculosis for places with a recognized high-risk group (prison, mining) and/or for places far from the health centre (difficulty in accessing the health system).

How to use these maps?

The maps delineate geographical areas that have different colour codes that represent the probability of having a lower (white areas) or higher (orange and red areas) incidence of tuberculosis compared to the national incidence estimated by WHO. For example, red areas predict a risk of tuberculosis 10 times higher than the national average. In a country where the estimated national incidence is 300 cases per 100,000 inhabitants per year, it is estimated that 3% of the population develops active tuberculosis each year in red areas, 1.5% in dark orange areas and less than 0.3% in lighter areas. By comparison, in a country with a lower estimated national incidence (e.g. 50 cases per 100,000 inhabitants per year), the incidence in red areas will also be lower than in a country with a very high incidence. For this reason, the maps are produced by country.

This tool therefore makes it possible to precisely target the places that should be given priority for intensified TB screening, prevention and treatment activities. Tools to plan and implement this type of activity based on a precise geographical location have been developed by Savics. This type of tool can be used in conjunction with the maps. In particular, they make it possible to monitor remotely the active screening work carried out by community actors in remote areas.

My country or province is not yet mapped

We are looking for partners around the world who would like to collaborate on the scientific validation of our approach. During the period 2019-2020, we invite any official body (national tuberculosis program or provincial tuberculosis coordination) wishing to collaborate in this direction to contact us in order to produce a map of the areas concerned and validate the data generated.

For any use of these maps outside this specific framework (calls for projects, activity reports, scientific communications), we ask you to make specific reference to this website as follows: Faccin M. and André E. Cartography of predicted tuberculosis hotspots in high burden settings. Available at: https://maurofaccin.github.io/cartotb

Limitations and evolution of the maps

The purpose of these maps is to predict the location of areas with a high incidence of tuberculosis higher than the national average. In countries with high tuberculosis incidence, tuberculosis affects each area, and effective disease control requires strengthening and supporting disease control activities, including in areas with lower predicted incidence. In some cases, it is possible that areas at high risk of TB may not be listed as red areas. This may be related to a low historical screening rate in these specific areas. It is therefore important that these maps be used as a guiding tool, but that TB program managers remain vigilant about the possibility that some high-risk populations may exist or emerge undetected by these maps.

The epidemiology of tuberculosis is set to evolve, thanks in part to the implementation of programs to improve the quality of screening and management of high-risk populations. Therefore, the annual updating of these maps is necessary to regularly reassess the impact of these activities and the possible emergence of new priority areas.

Contact with researchers:

• Dr Mauro Faccin
• Dr Emmanuel André

A collaboration between:

With the support of: