Incorporating Scale Dependence in Disease Burden Estimates: The Case of Human African Trypanosomiasis in Uganda.

Background: The WHO has established the disability-adjusted life year (DALY) as a metric for measuring the burden of human disease and injury globally. However, most DALY estimates have been calculated as national totals. We mapped spatial variation in the burden of human African trypanosomiasis (HAT) in Uganda for the years 2000–2009. This represents the first geographically delimited estimation of HAT disease burden at the sub-country scale. Methodology/Principal Findings: Disability-adjusted life-year (DALY) totals for HAT were estimated based on modelled age and mortality distributions, mapped using Geographic Information Systems (GIS) software, and summarised by parish and district. While the national total burden of HAT is low relative to other conditions, high-impact districts in Uganda had DALY rates comparable to the national burden rates for major infectious diseases. The calculated average national DALY rate for 2000–2009 was 486.3 DALYs/100 000 persons/year, whereas three districts afflicted by rhodesiense HAT in southeastern Uganda had burden rates above 5000 DALYs/100 000 persons/year, comparable to national GBD 2004 average burden rates for malaria and HIV/AIDS. Conclusions/Significance: These results provide updated and improved estimates of HAT burden across Uganda, taking into account sensitivity to under-reporting. Our results highlight the critical importance of spatial scale in disease burden analyses. National aggregations of disease burden have resulted in an implied bias against highly focal diseases for which geographically targeted interventions may be feasible and cost-effective. This has significant implications for the use of DALY estimates to prioritize disease interventions and inform cost-benefit analyses. Author Summary: Since the 1990s the World Health Organisation has established the disability-adjusted life year (DALY) as a metric for the burden of human disease and injury. However, disease burden has primarily been estimated at the national scale, which does not account for sub-country variations in burden levels. We used the case of human African trypanosomiasis (HAT), a highly focal NTD, in Uganda to calculate and map burden in DALYs. Our results show that HAT burden is highly sensitive to under-reporting estimates, and is particularly high in heavily affected parishes and districts of Uganda. Some districts in southeastern Uganda had HAT burden rates comparable to the national burden rates of major infectious diseases such as malaria and HIV/AIDS. Thus, the spatial scale of burden estimation is crucial, especially for focal diseases such as HAT, and national-level estimates may not reflect the level of impact in afflicted communities. We recommend sub-country burden estimation to identify key areas for prioritization of disease surveillance and targeted interventions. [ABSTRACT FROM AUTHOR]