Location-allocation modeling identifies strategic health facilities to expand access to snakebite antivenom in the Brazilian Amazon
- 1Federal University of Maranhao
Abstract
BackgroundSnakebite envenoming is a major cause of preventable death and disability in the Brazilian Amazon, where long distances, sparse roads, and dependence on river transport delay access to antivenom. We developed location-allocation models to identify community health centers that could strategically expand access to antivenom in Amazonas State, Brazil.
Methodology/Principal FindingsWe conducted an ecological geospatial study using a 2025 WorldPop population surface, locations of existing and candidate health facilities, and a multimodal road-and-river transportation network derived from OpenStreetMap and HydroSHEDS. Population demand was represented by 7,065 populated centroids, including 1,586 within Indigenous territories. We applied a maximize-coverage algorithm with a six-hour travel-time threshold. Two models were developed: one for Amazonas excluding Manaus and one for populations living in Indigenous territories. Both models began with 77 facilities already providing antivenom and progressively added candidate community health centers until coverage gains plateaued. The plateau occurred at 110 facilities, corresponding to 33 additional centers. In the model excluding Manaus, this configuration covered 1,118,831 people, or 75.11% of the target population; 87.61% of those covered could reach care within three hours. In Indigenous territories, coverage increased from 50.55% to 69.50%, reaching 50,434 people, of whom 81.39% were within three hours of care. Validation used 3,595 snakebite notifications from the 30 highest-burden municipalities in the Brazilian Notifiable Diseases Information System during 2023-2025. The median proportion reaching care within six hours was 40.81% in observed data and 72.17% in model estimates.
Conclusions/SignificanceStrategically equipping 33 additional existing community health centers could substantially expand timely access to antivenom, particularly in rural and Indigenous areas. Location-allocation modeling that incorporates river transportation can support evidence-based decentralization of time-sensitive health services in geographically complex settings.
Author SummarySnakebite is a serious but preventable health problem in the Brazilian Amazon. Antivenom can save lives, but many people live far from the hospitals that currently provide it, and travel often depends on rivers rather than roads. We investigated whether existing community health centers could be selected strategically to bring treatment closer to rural and Indigenous communities in Amazonas state.
We combined population maps, locations of health facilities, and road and river routes to estimate how long people would need to travel to receive antivenom. We found that adding antivenom services to 33 carefully selected community health centers, in addition to the 77 facilities already providing treatment, produced most of the achievable improvement in coverage. This arrangement could provide access within six hours for about three-quarters of the population, and nearly seven in ten people living in Indigenous territories. When we compared the estimates with snakebite notifications from 2023 to 2025, the proposed distribution showed a larger proportion of people reaching care within six hours. Our findings show how existing health infrastructure and river transportation data can guide practical decisions about where to decentralize antivenom treatment.
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BibTeX
@misc{campos2026locationallocation,
title = {{Location-allocation modeling identifies strategic health facilities to expand access to snakebite antivenom in the Brazilian Amazon}},
author = {M. A. Garcia Campos and T. A. H. Rocha and J. V. Perez de Souza and L. S. Murase and F. Murta and M. A. Sartim and J. Sachett and A. Seabra de Farias and V. Azevedo Machado and F. H. Wen and C. A. Staton and W. M. Monteiro and C. J. Gerardo and J. R. Nickenig Vissoci},
howpublished = {medRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.28.26360696},
url = {https://www.medrxiv.org/content/10.64898/2026.08.28.26360696v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Location-allocation modeling identifies strategic health facilities to expand access to snakebite antivenom in the Brazilian Amazon
AU - M. A. Garcia Campos
AU - T. A. H. Rocha
AU - J. V. Perez de Souza
AU - L. S. Murase
AU - F. Murta
AU - M. A. Sartim
AU - J. Sachett
AU - A. Seabra de Farias
AU - V. Azevedo Machado
AU - F. H. Wen
AU - C. A. Staton
AU - W. M. Monteiro
AU - C. J. Gerardo
AU - J. R. Nickenig Vissoci
PY - 2026
DA - 2026/08/28
PB - medRxiv
DO - 10.64898/2026.08.28.26360696
UR - https://www.medrxiv.org/content/10.64898/2026.08.28.26360696v1
AB - BackgroundSnakebite envenoming is a major cause of preventable death and disability in the Brazilian Amazon, where long distances, sparse roads, and dependence on river transport delay access to antivenom. We developed location-allocation models to identify community health centers that could strategically expand access to antivenom in Amazonas State, Brazil. Methodology/Principal FindingsWe conducted an ecological geospatial study using a 2025 WorldPop population surface, locations of existing and candidate health facilities, and a multimodal road-and-river transportation network derived from OpenStreetMap and HydroSHEDS. Population demand was represented by 7,065 populated centroids, including 1,586 within Indigenous territories. We applied a maximize-coverage algorithm with a six-hour travel-time threshold. Two models were developed: one for Amazonas excluding Manaus and one for populations living in Indigenous territories. Both models began with 77 facilities already providing antivenom and progressively added candidate community health centers until coverage gains plateaued. The plateau occurred at 110 facilities, corresponding to 33 additional centers. In the model excluding Manaus, this configuration covered 1,118,831 people, or 75.11% of the target population; 87.61% of those covered could reach care within three hours. In Indigenous territories, coverage increased from 50.55% to 69.50%, reaching 50,434 people, of whom 81.39% were within three hours of care. Validation used 3,595 snakebite notifications from the 30 highest-burden municipalities in the Brazilian Notifiable Diseases Information System during 2023-2025. The median proportion reaching care within six hours was 40.81% in observed data and 72.17% in model estimates. Conclusions/SignificanceStrategically equipping 33 additional existing community health centers could substantially expand timely access to antivenom, particularly in rural and Indigenous areas. Location-allocation modeling that incorporates river transportation can support evidence-based decentralization of time-sensitive health services in geographically complex settings. Author SummarySnakebite is a serious but preventable health problem in the Brazilian Amazon. Antivenom can save lives, but many people live far from the hospitals that currently provide it, and travel often depends on rivers rather than roads. We investigated whether existing community health centers could be selected strategically to bring treatment closer to rural and Indigenous communities in Amazonas state. We combined population maps, locations of health facilities, and road and river routes to estimate how long people would need to travel to receive antivenom. We found that adding antivenom services to 33 carefully selected community health centers, in addition to the 77 facilities already providing treatment, produced most of the achievable improvement in coverage. This arrangement could provide access within six hours for about three-quarters of the population, and nearly seven in ten people living in Indigenous territories. When we compared the estimates with snakebite notifications from 2023 to 2025, the proposed distribution showed a larger proportion of people reaching care within six hours. Our findings show how existing health infrastructure and river transportation data can guide practical decisions about where to decentralize antivenom treatment.
ER -