Dididi project

Connecting diagnostic evidence, public-health data and decisions that protect underserved communities.

For health authorities, the challenge of helminth infections extends beyond delivering treatment. Programmes must establish where infection persists, which populations are being missed, whether interventions are reducing disease and what evidence justifies a change in strategy. Surveillance provides the information needed to answer these questions over time.

This is particularly important for soil-transmitted helminthiases and schistosomiasis in sub-Saharan Africa. Their distribution is uneven, diagnostic methods have limitations, and healthcare access influences which infections become visible in routine records. A national treatment total or a district prevalence estimate can therefore leave important questions unanswered.

Effective surveillance connects information to an agreed response. It enables authorities to target investigation, allocate resources, review programme performance and maintain progress as infection levels decline. DIDIDI is working within this agenda by developing connected diagnostic approaches that link individual, community and environmental information with health-system decision-making.

A substantial burden requires evidence at the scale of action

WHO estimates that soil-transmitted helminth infections affect approximately 1.5 billion people worldwide, particularly in communities with inadequate sanitation. [1] For schistosomiasis, at least 253.7 million people required preventive treatment in 2024; WHO estimates that 93.9% of those requiring treatment live in Africa. The preventive-treatment population is not a count of laboratory-confirmed infections. [2]

These figures establish the importance of the problem but cannot determine an individual district’s intervention priorities. Authorities need information about local infection patterns, affected groups and programme delivery.

The necessary geographical resolution depends on the decision. National summaries support budgeting and reporting. District information supports supervision and deployment. Community-level evidence may be needed to investigate persistent transmission or identify locations hidden within a lower-prevalence district.

Surveillance planning should begin by defining the decision, the population and the geographical unit. Collecting more data is useful only when the additional detail improves a decision that the programme has the capacity to implement.

Treatment delivery and health impact are different measures

The number of people treated is an important operational measure. It describes programme activity, but it does not independently demonstrate that infection intensity, morbidity or transmission has declined.

WHO’s 2024 monitoring and evaluation framework for schistosomiasis and soil-transmitted helminthiases supports programme managers in selecting indicators, organising impact assessments and interpreting results. It places evidence at the centre of adapting control programmes. [3]

Authorities should distinguish several questions: were planned activities completed, did eligible people receive treatment, did infection outcomes improve, and are the changes sufficient to justify modifying the programme? These questions require different denominators and sometimes different data sources.

For example, a treatment campaign can report strong delivery while a follow-up survey identifies persistent infection in particular communities. The appropriate response is to investigate delivery, participation, continuing exposure and diagnostic comparability. It would be premature to interpret that pattern as proof of drug resistance or to assume that the campaign had no benefit.

Combine complementary sources without treating them as interchangeable

A surveillance system can draw on routine care, planned surveys, treatment records and environmental observations. Each source has a different relationship to the population and to infection.

Information source	Main contribution	Important interpretation limit
Routine health-facility records	Continuous information about diagnosed patients, care and service demand	Depends on attendance, clinical suspicion, testing and reporting
Designed population surveys	Estimates of infection in a defined population	Depends on sampling, participation, timing and diagnostic method
Treatment programme records	Delivery, coverage and implementation gaps	Does not directly measure infection outcomes
Repeated sentinel observations	Trends at selected locations	May not represent unsampled communities
Environmental or snail surveillance	Evidence about parasite presence and possible transmission settings	Does not directly measure individual infection or human prevalence

The table provides an analytical framework for combining evidence. It should inform a country-specific surveillance plan rather than substitute for disease-specific guidance.

Triangulation means examining whether these sources tell a coherent story while retaining their separate meanings. An increase in diagnosed cases after laboratory expansion, for example, may reflect improved detection. A survey can help investigate whether population infection also changed. The two observations should be connected analytically, not merged into a single unqualified case count.

Routine facility data need context and quality checks

WHO’s 2025 guidance on routine schistosomiasis data addresses facility indicators, trend interpretation, programme performance and data quality. It recognises the value of routine reporting alongside the limitations involved in using these data. [4]

Authorities should examine recorded cases together with testing volume, reporting completeness and changes in service availability. A low case count from a facility with little diagnostic capacity has a different meaning from a low count under consistent testing and reporting.

Standard definitions are essential. Suspected and confirmed cases, newly diagnosed patients and repeat visits, and routine care and survey encounters should remain distinguishable. Where information systems permit, diagnostic method and specimen type should accompany results.

Missing reports also need a visible status. A blank cell should not automatically become a zero, and a zero should not automatically be interpreted as absence of disease. Regular checks with facilities can establish whether an apparent decline reflects epidemiology, service interruption or reporting failure.

Spatial heterogeneity makes survey design a policy issue

Schistosomiasis transmission can be highly focal. Communities within the same administrative area may have different risks, meaning that an average can obscure locations requiring attention.

Fornace and colleagues evaluated survey designs across plausible schistosomiasis distributions in sub-Saharan Africa using geostatistical modelling. Their findings highlight the importance of spatial structure and show how finer implementation units can improve treatment classification, while increasing survey costs. [5]

The implication is not that every programme needs maximal sampling everywhere. Authorities should weigh the cost of additional information against the consequences of misclassification. More detailed investigation may be particularly useful near decision thresholds, in areas with suspected hotspots or where existing evidence is sparse.

Survey reports should identify the sampled population and locations, describe uncertainty and explain where extrapolation is being made. School-based evidence must also be interpreted in relation to school attendance and the groups the programme seeks to protect. The decision team should know who is represented and who may be absent.

Diagnostic performance shapes the surveillance picture

Recorded infection is partly a product of the diagnostic method used. Sensitivity can vary with species, infection intensity and sampling effort. A meta-analysis of soil-transmitted helminth diagnostics found important differences across methods and lower sensitivity in lighter infections. [6]

This affects comparisons over time. If a programme moves from one method to another, an apparent rise may reflect improved detection rather than increased transmission. A decline can similarly be difficult to interpret if sample numbers, preparation or quality assurance have changed.

WHO target product profiles for schistosomiasis and soil-transmitted helminths explicitly connect diagnostic development with programme monitoring and surveillance needs. They address the limitations of existing tools and the decisions new tests should support. [7,8]

Authorities should preserve diagnostic metadata and plan method transitions carefully. Depending on the change, parallel testing or a bridging evaluation may be needed. Thresholds derived for one diagnostic approach should not be transferred mechanically to another. The applicable WHO and national guidance should determine how test results inform programme classification.

Declining infection increases the importance of credible surveillance

As control programmes succeed, remaining infections may become more difficult to detect and more concentrated geographically. Surveillance must remain capable of identifying residual risk while avoiding unsupported conclusions from isolated or uncertain findings.

WHO’s schistosomiasis diagnostic profiles describe the need for sensitive detection in low-intensity infections and approaches combining screening and confirmation for surveillance. [7] This illustrates why a diagnostic strategy designed for a high-burden baseline survey may not answer every question at a later programme stage.

Authorities must also distinguish elimination as a public-health problem from interruption of transmission. The former concerns achieving defined disease-control criteria; it does not necessarily mean that no infection remains. WHO’s control and elimination guideline addresses prevalence-based interventions and measures supporting progress towards these goals. [9]

Programme transitions should therefore use the relevant disease-specific criteria and evidence requirements. Surveillance funding and responsibilities need to continue through those transitions, with a clear plan for investigating signals and responding if risk returns.

Define a small set of indicators that supports decisions

A practical information system should prioritise measures that users can interpret and act upon. The following set is a starting point for discussion, not a prescribed WHO indicator list.

Indicator	Decision it can support	Quality question
Survey prevalence and infection intensity	Review intervention strategy under applicable guidance	Are sampling and diagnostics comparable?
Treatment coverage by eligible population and area	Identify delivery or participation gaps	Is the denominator credible, and does the numerator reflect treatment received?
Testing volume and positivity by method	Review diagnostic access and investigate changes	Did testing criteria or capacity change?
Reporting completeness and timeliness	Target supervision and reporting support	Which sites or periods are missing?
Persistent local infection after interventions	Prioritise investigation and coordinated response	Could exposure, coverage or measurement explain the pattern?
Time from a verified signal to response	Assess whether surveillance leads to action	Are responsibilities and resources defined?

Disaggregation should serve a purpose. Geography, age and sex may reveal gaps hidden within an aggregate, but detailed reporting must remain feasible and protect confidentiality.

Indicator definitions, denominators and update schedules should be available to every reporting level. A small, consistently collected dataset is more useful than a large dashboard whose measures are incomplete or misunderstood.

Environmental surveillance can add information, with defined limits

Environmental approaches can investigate parasite presence outside the clinic. Sengupta and colleagues developed an environmental DNA method for detecting Schistosoma mansoni in water and tested its field application at known transmission sites in Kenya. This research demonstrates a potential contribution to environmental surveillance. [10]

Detection of parasite DNA is not equivalent to a count of infected people, and it does not automatically demonstrate viable infective stages or the magnitude of human risk. Sampling location, water movement, assay specificity and timing all affect interpretation.

Authorities considering these tools should establish the intended use and the validation required. An environmental signal might trigger repeat sampling, a targeted human survey or assessment of a water-contact site. The response should be agreed before routine implementation.

Environmental information can complement human and snail investigations. Its value lies in improving where and when authorities investigate or intervene. It should not replace established evidence requirements for treatment changes or elimination decisions without appropriate validation.

Climate information should support locally validated risk assessment

Temperature, rainfall and water conditions influence parts of the schistosome–snail transmission system. A systematic review of schistosomiasis and climate change found that expected effects vary by region, with uncertainty about the direction of changes in some African settings. [11]

This argues for local investigation rather than assuming that warming produces a uniform increase in risk. Weather, land use, water infrastructure, human behaviour and programme delivery can interact, and a statistical association alone does not establish causation.

An authority incorporating climate information should define its operational purpose. Possible uses include prioritising surveillance after environmental change or planning fieldwork when access and exposure patterns shift. Predictive models require validation on data beyond those used to develop them, with attention to false alerts and missed signals.

Forecasts should display uncertainty and remain distinguishable from observed infection data. Their usefulness depends on whether they improve an actual decision, such as selecting an investigation site, rather than on model accuracy alone.

Digital integration must reduce fragmentation

Connected information systems can make diagnostic evidence available for clinical care and public-health review. However, introducing a new app or dashboard can also create duplicate reporting unless integration is planned from the outset.

Authorities should specify which system holds the authoritative record, how sites and administrative units are identified, and how validated results are transferred. Existing platforms, including national health-information systems and WHO’s ESPEN resources, should inform the architecture. ESPEN provides access to data and maps supporting neglected tropical disease decisions. [12]

Operational design also needs to cover offline use, synchronisation, corrections and support. Staff should be able to identify an invalid result or amended record rather than having uncertainty disappear during data transfer.

Data governance belongs within this design. Individual records need appropriate access controls; public maps should avoid exposing identifiable households or patients. Authorities should define responsibilities for data stewardship, sharing, retention and incident response, consistent with applicable national requirements.

Turn signals into a documented response

A surveillance system needs an agreed sequence from detection to review and action. A district team should know which findings require routine discussion, which require verification and which justify prompt escalation.

Consider an illustrative scenario: reported schistosomiasis positivity increases in several facilities near a water-contact area. The first step is to review testing volume, methods and reporting. The next may be to compare existing survey and treatment information, consult local services and undertake targeted investigation if the signal remains credible.

The response might then involve improving treatment access, investigating coverage gaps or coordinating with water and sanitation teams. It should follow the evidence and applicable guidance rather than an automatic rule that every increase requires the same intervention.

Every response needs an owner, a timetable and a way to assess completion. Feedback to the reporting facilities and communities helps close the loop. Surveillance becomes a public-health service when information leads to an accountable response.

DIDIDI: linking diagnostic innovation with public-health intelligence

DIDIDI is developing affordable digital diagnostics and connected information approaches for underserved rural communities in sub-Saharan Africa. Its planned work links individual testing, community environmental samples and national health-information systems. [13]

Community diagnostic research includes field-deployable molecular methods and evaluation of how environmental signals relate to human prevalence in Uganda and Kenya. The project also plans integration with DHIS2 and analysis of climate and health information. These are research objectives requiring validation, not established early-warning performance claims. [13]

The broader project objective is to make low-cost diagnostics and secure data connections useful for understanding disease dynamics, improving care pathways and informing climate-adaptive public-health policies. [14]

For health authorities, the relevant contribution is the planned connection between measurements and decisions. Participation can help define which signals are useful, what existing systems must receive the data and what evidence is needed before a new approach enters routine surveillance.

Invest in the capacity to use evidence

Surveillance requires sustained funding for diagnostics, sampling, quality assurance, analysis and response. Hardware and software budgets should be accompanied by staff development, maintenance and protected time for reviewing results.

WHO’s recent monitoring and evaluation guidance frames evidence as a basis for adapting interventions and allocating resources as disease patterns change. [15] Authorities can put this into practice by assigning analytical responsibilities at each level and linking review meetings to budget and programme planning.

The central question is whether surveillance makes uncertainty manageable. A credible system shows where evidence is strong, where gaps remain and what action is justified. For helminth infections in sub-Saharan Africa, that capacity supports more appropriate interventions, greater attention to underserved populations and sustained progress towards public-health goals.

References

World Health Organization. Soil-transmitted helminth infections. WHO.
World Health Organization. Schistosomiasis. Fact sheet, 23 February 2026. WHO.
World Health Organization. Assessing schistosomiasis and soil-transmitted helminthiases control programmes: Monitoring and evaluation framework. 2024. WHO publication record.
World Health Organization. Routine health information system and health facility data for neglected tropical diseases: Schistosomiasis. 2025. WHO.
Fornace KM, Fronterrè C, Fleming FM, et al. Evaluating survey designs for targeting preventive chemotherapy against Schistosoma haematobium and Schistosoma mansoni across sub-Saharan Africa: a geostatistical analysis and modelling study. Parasites & Vectors. 2020;13:555. doi.org/10.1186/s13071-020-04413-7.
Nikolay B, Brooker SJ, Pullan RL. Sensitivity of diagnostic tests for human soil-transmitted helminth infections: a meta-analysis in the absence of a true gold standard. International Journal for Parasitology. 2014;44(11):765–774. PubMed.
World Health Organization. Diagnostic target product profiles for monitoring, evaluation and surveillance of schistosomiasis control programmes. 2021. WHO.
World Health Organization. Diagnostic target product profile for monitoring and evaluation of soil-transmitted helminth control programmes. 2021. WHO.
World Health Organization. WHO guideline on control and elimination of human schistosomiasis. 2022. WHO.
Sengupta ME, Hellström M, Kariuki HC, et al. Environmental DNA for improved detection and environmental surveillance of schistosomiasis. Proceedings of the National Academy of Sciences. 2019;116(18):8931–8940. doi.org/10.1073/pnas.1815046116.
Stensgaard AS, Vounatsou P, Sengupta ME, Utzinger J. Schistosomes, snails and climate change: Current trends and future expectations. Acta Tropica. 2019;190:257–268. doi.org/10.1016/j.actatropica.2018.09.013.
World Health Organization, Regional Office for Africa. Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN). ESPEN portal.
DIDIDI consortium. Project description. DIDIDI.
European Commission, CORDIS. DIGITAL DASHBOARDS IN DIAGNOSTIC INNOVATIONS—DIDIDI. Grant agreement 101190614. CORDIS.
World Health Organization. New guidance to accelerate elimination of schistosomiasis and intestinal helminthiasis. 31 October 2024. WHO.

Sources accessed on 13 October 2026. The indicator table and response scenario are practical analytical examples, not a replacement for WHO or national programme algorithms. DIDIDI activities are described as research objectives.