Utility of surveillance data for planning for dengue elimination in Yogyakarta, Indonesia: a scenario tree modelling approach
Authors: Bannister-Tyrrell Melanie , Hillman Alison , Indriani Citra , Ahmad Riris Andono , Utarini Adi , Simmons Cameron P. , Anders Katherine L. , Sargeant Evan 
Published: March 2023

AbstractIntroductionField trials and mathematical modelling studies suggest that elimination of dengue transmission may be possible through widespread release ofAedes aegyptimosquitoes infected with the insect bacteriumWolbachia pipientis(wMel strain), in conjunction with routine dengue control activities. This study aimed to develop a modelling framework to guide planning for the potential elimination of locally-acquired dengue in Yogyakarta, a city of almost 400,000 people in Java, Indonesia.MethodsA scenario tree modelling approach was used to estimate the sensitivity of the dengue surveillance system (including routine hospital-based reporting and primary-care based enhanced surveillance), and time required to demonstrate elimination of locally-acquired dengue in Yogyakarta city, assuming the detected incidence of dengue decreases to zero in the future. Age and gender were included as risk factors for dengue, and detection nodes included the probability of seeking care, probability of sample collection and testing, diagnostic test sensitivity, and probability of case notification. Parameter distributions were derived from health system data or estimated by expert opinion. Alternative simulations were defined based on changes to key parameter values, separately and in combination.ResultsFor the default simulation, median surveillance system sensitivity was 0.131 (95% PI 0.111 – 0.152) per month. Median confidence in dengue elimination reached 80% after a minimum of 13 months of zero detected dengue cases and 90% confidence after 25 months, across different scenarios. The alternative simulations investigated produced relatively small changes in median system sensitivity and time to elimination.ConclusionThis study suggests that with a combination of hospital-based surveillance and enhanced clinic-based surveillance for dengue, an acceptable level of confidence (80% probability) in the elimination of locally acquired dengue can be reached within 2 years. Increasing the surveillance system sensitivity could shorten the time to first ascertainment of elimination of dengue and increase the level of confidence in elimination.Key messagesWhat is already known on this topic - summarise the state of scientific knowledge on this subject before you did your study and why this study needed to be doneThe incidence of dengue, a mosquito-borne viral disease, has increased worldwide in recent decades. However, a novel vector control intervention based on the release ofAedes aegyptivectors infected with thewMel strain ofWolbachia pipientisbacteria, which inhibits arboviral infection and transmission in mosquitoes, has been shown to substantially decrease the incidence of dengue. A randomised controlled trial in Yogyakarta city, Indonesia, demonstrated a 77% reduction in dengue incidence in areas treated with theWolbachiaintervention. Field-based and modelling studies have predicted that theWolbachiaintervention could reduce dengue transmission to the point of elimination of locally-acquired dengue. The feasibility of elimination of dengue as a public health problem through city-wide deployment ofWolbachia intervention, complemented by other vector control measures and enhanced clinical surveillance, is being tested in Yogyakarta city, Indonesia, as part of an additional study. For any planned infectious disease elimination program, demonstrating that elimination has been achieved requires effective surveillance for dengue and robust statistical methods. The aim of this study was to develop a scenario tree modelling framework to guide planning for the potential elimination of locally acquired dengue in Yogyakarta city, Indonesia.What this study adds - summarise what we now know as a result of this study that we did not know beforeThis study constructed a scenario tree model to represent the dengue surveillance system in Yogyakarta city, including hospital-based and clinic-based surveillance. The model was parameterised with risk factors for dengue, as well as the steps in the surveillance pathway, from healthcare seeking to notification of a positive case. This study suggests that with a combination of hospital-based surveillance and enhanced clinic-based surveillance for clinical dengue cases, an acceptable level of confidence (80% probability) in the elimination of locally acquired dengue in Yogyakarta city can be reached within 2 years of the last detected case. This suggests that routine clinic-based and hospital-based passive surveillance for dengue is sufficiently sensitive to plan for and confirm elimination of local dengue transmission in Yogyakarta city.How this study might affect research, practice or policy - summarise the implications of this studyThe findings suggest that pragmatic demonstration of the elimination of locally-acquired dengue can be reached in a shorter timeframe than the alternative approach of convening an independent expert review panel, as commonly used for other infectious disease elimination programs. The scenario tree modelling framework offers a replicable, robust method for planning and assessing progress towards elimination of dengue as a public health problem following full implementation of theWolbachiaintervention and enhanced clinic-based dengue surveillance in Yogyakarta city, Indonesia. The framework can be readily expanded and adapted to different geographic settings where theWolbachiaintervention is also being implemented to control and eliminate dengue.