Spatial Epidemiology, Geographic Clustering, and Determinants of HIV Infection and HIV Testing Gaps among Ethiopian Adults: Evidence from the 2024/25 Ethiopian Demographic and Health Survey

HIV remains a persistent global health challenge, even as medical advances have turned a once-fatal diagnosis into a manageable condition for many. The virus spreads through specific behaviors and circumstances, but its impact is rarely felt evenly across a country. Instead, the burden of infection and the access to life-saving tests often cluster in specific neighborhoods, cities, or regions, creating pockets of high risk surrounded by areas of lower risk. Understanding these patterns requires looking beyond national averages. When health officials rely only on a single number for an entire country, they miss the local realities where transmission is concentrated or where people cannot reach testing services. To see these hidden patterns, researchers use a field called spatial epidemiology, which combines medical data with geography to map where diseases occur and why they group together in certain places.

A recent study published in 2026 brings this approach to Ethiopia, using the most comprehensive health data available from the nation. The researchers analyzed information from the 2024/25 Ethiopian Demographic and Health Survey, a massive project that interviewed tens of thousands of adults and confirmed their HIV status through laboratory blood tests. By linking these medical results with the exact locations where people were surveyed, the team could create a detailed map of the epidemic. They looked for two distinct things: where the virus was actually present in the population, and where people were failing to get tested for it. The goal was to move past broad national estimates and identify the specific communities that needed the most urgent attention.

The study began by confirming that HIV infection in Ethiopia is not scattered randomly across the landscape. Instead, the virus shows a clear tendency to cluster. The researchers found that neighboring areas often shared similar infection rates, suggesting that local factors like population movement, economic conditions, or healthcare access drive the spread of the virus in specific zones. The overall rate of infection across the country was found to be just under one percent, a figure that might suggest the epidemic is under control. However, the map told a different story. The analysis revealed distinct hotspots where the risk was significantly higher than the national average. These high-risk areas were concentrated in the Gambella region, the capital city of Addis Ababa, the Harari region, and parts of western Ethiopia. In these specific locations, the risk of infection was many times higher than in the surrounding areas, indicating that a uniform national strategy would fail to reach the people most in need.

While the virus clustered in some places, the lack of testing clustered in others, creating a different kind of map. The researchers discovered that nearly half of all adults in the study had never been tested for HIV. This gap in testing was not evenly distributed either; it formed massive clusters in the Somali region, the Sidama region, the South Ethiopia region, and parts of eastern Oromia. In these areas, the barriers to getting a test were so high that large populations remained unaware of their status. The study showed that the places with the highest infection rates were not always the same as the places with the biggest testing gaps. This distinction is crucial: some areas need more treatment and prevention because the virus is spreading rapidly, while others need more testing services simply because people cannot access them.

The investigation also looked at who was most likely to be infected and who was least likely to get tested. The data showed that older adults, particularly those between 45 and 59 years old, carried the highest burden of infection. This suggests that many people living with HIV in Ethiopia were infected years ago and have survived due to better treatment, shifting the demographic of the epidemic toward older age groups. Women were also more likely to be infected than men. On the other hand, the people most likely to have never been tested were younger, male, less educated, and living in poverty. These individuals often lacked access to media that could inform them about testing or lived in communities where healthcare services were scarce. The study found that where a person lived mattered as much as their personal circumstances; living in the Somali region, for instance, made a person far more likely to have never been tested than living in other parts of the country.

To make sense of these patterns, the researchers used advanced mapping tools to predict where the virus and the testing gaps might be, even in areas where no one had been surveyed. These predictions confirmed that the risk was highest in the eastern and southeastern parts of the country for testing gaps, while the infection risk remained concentrated in the west and the capital. The study ruled out the idea that the epidemic was a uniform wave moving across the country; instead, it is a patchwork of intense local outbreaks and service deserts. The researchers were careful to note that their findings were based on a single snapshot in time, so they could not prove exactly why these patterns existed, but the evidence for the clustering itself was strong and statistically significant.

The implications of these findings are clear for public health leaders. A one-size-fits-all approach to fighting HIV in Ethiopia will not work because the problem looks different in every corner of the country. The study suggests that resources must be directed with surgical precision. In the hotspots like Gambella and Addis Ababa, the focus should be on stopping transmission and linking infected individuals to treatment. In the testing deserts like the Somali region, the priority must be bringing testing services directly to communities that have been left behind. By using maps to guide their decisions, health officials can ensure that prevention and care reach the specific people and places that need them most, rather than spreading resources too thinly across the entire nation. This shift toward targeted, geography-based strategies offers a path to finally control the epidemic and ensure that no one is left undiagnosed.