Integrating Facility-Based Surveillance With Healthcare Utilization Surveys to Estimate Enteric Fever Incidence: Methods and Challenges

OBJECTIVE:
Cohort studies and facility-based sentinel surveillance are common approaches to characterizing infectious disease burden, but present trade-offs; cohort studies are resource-intensive and may alter disease natural history, while sentinel surveillance underestimates incidence in the population. Hybrid surveillance, whereby facility-based surveillance is paired with a community-based healthcare utilization assessment, represents an alternative approach to generating population-based disease incidence estimates with moderate resource investments. Here, we discuss this method in the context of the Surveillance for Enteric Fever in Asia Project (SEAP) study.
RESULTS:
Hybrid surveillance is not without limitations, but for relatively uncommon diseases (<1% per year), it represents a powerful and efficient means for generating estimates of disease incidence at a fraction of the cost of cohort studies. With periodic healthcare utilization assessments alongside continuous hospital surveillance, longitudinal monitoring of trends in incidence of enteric fever may be maintained in resource-limited settings, providing policy-relevant data, including in the context of vaccine introduction. Careful attention to potential sources of bias in system design, implementation, and data analysis can improve the accuracy of incidence estimates and result in rigorous and sustainable systems for population-based infectious disease surveillance.