Fine-scale estimation of effective reproduction numbers for dengue surveillance

Soh, Stacy; Ong, Janet; Seah, Annabel; Dickens, Borame Sue Lee; Tan, Ken Wei; Koo, Joel Ruihan; Cook, Alex R.; Richards, Daniel R.; Gaw, Leon Yan-Feng; Ng, Lee Ching; Lim, Jue Tao

doi:10.1371/journal.pcbi.1009791

Cited by 7 publications

(4 citation statements)

References 53 publications

(85 reference statements)

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“…The associations were studied by sub-setting our datasets into the primary type of housing found in each spatial unit, with associations for each exposure estimated to be generally consistent across datasets. The findings obtained from this study build upon previous work [ 26 , 27 , 28 , 29 ] that sought to establish a thorough understanding of DENV transmission.…”

Section: Discussionsupporting

confidence: 63%

Associations between Dengue Incidence, Ecological Factors, and Anthropogenic Factors in Singapore

Tewari,

Guo,

Dickens

et al. 2023

Viruses

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Singapore experiences endemic dengue. Vector control remains the primary means to reduce transmission due to the lack of available therapeutics. Resource limitations mean that vector-control tools need to be optimized, which can be achieved by studying risk factors related to disease transmission. We developed a statistical modelling framework which can account for a high-resolution and high-dimensional set of covariates to delineate spatio-temporal characteristics that are associated with dengue transmission from 2014 to 2020 in Singapore. We applied the proposed framework to two distinct datasets, stratified based on the primary type of housing within each spatial unit. Generalized additive models reveal non-linear exposure responses between a large range of ecological and anthropogenic factors as well as dengue incidence rates. At values below their mean, lesser mean total daily rainfall (Incidence rate ratio (IRR): 3.75, 95% CI: 1.00–14.05, Mean: 4.40 mm), decreased mean windspeed (IRR: 3.65, 95% CI: 1.87–7.10, Mean: 4.53 km/h), and lower building heights (IRR: 2.62, 95% CI: 1.44–4.77, Mean: 6.5 m) displayed positive associations, while higher than average annual NO2 concentrations (IRR: 0.35, 95% CI: 0.18–0.66, Mean: 13.8 ppb) were estimated to be negatively associated with dengue incidence rates. Our study provides an understanding of associations between ecological and anthropogenic characteristics with dengue transmission. These findings help us understand high-risk areas of dengue transmission, and allows for land-use planning and formulation of vector control policies.

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Section: Discussionsupporting

confidence: 63%

Associations between Dengue Incidence, Ecological Factors, and Anthropogenic Factors in Singapore

Tewari,

Guo,

Dickens

et al. 2023

Viruses

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“…aegypti. Impervious surfaces, which absorb greater amounts of heat than pervious ones during the day and release heat more slowly at night, are positively associated with the effective reproduction number of dengue in Singapore [34]. Additionally, these surfaces have been associated with vectorial capacity in Athens, Georgia, US [35].…”

Section: Discussionmentioning

confidence: 99%

Spatial Methods for Inferring Extremes in Dengue Outbreak Risk in Singapore

Soh

Seah

Ong

et al. 2022

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Dengue is a major vector-borne disease worldwide. Here, we examined the spatial distribution of extreme weekly dengue outbreak risk in Singapore from 2007 to 2020. We divided Singapore into equal-sized hexagons with a circumradius of 165 m and obtained the weekly number of dengue cases and the surface characteristics of each hexagon. We accounted for spatial heterogeneity using max-stable processes. The 5-, 10-, 20-, and 30-year return levels, or the weekly dengue case counts expected to be exceeded once every 5, 10, 20, and 30 years, respectively, were determined for each hexagon conditional on their surface characteristics remaining constant over time. The return levels were higher in the country’s east, with the maximum weekly dengue cases per hexagon expected to exceed 51 at least once in 30 years in many areas. The surface characteristics with the largest impact on outbreak risk were the age of public apartments and the percentage of impervious surfaces, where a 3-year and 10% increase in each characteristic resulted in a 3.8% and 3.3% increase in risk, respectively. Vector control efforts should be prioritized in older residential estates and places with large contiguous masses of built-up environments. Our findings indicate the likely scale of outbreaks in the long term.

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“…aegypti vector. An increase in the ambient temperature between 25°C and 35°C accelerates the life cycle of mosquito vectors [ 40 ] and reduces the EIP of the dengue virus in the vector [ 41 ], thereby increasing the transmission potential of dengue virus [ 42 ]. For example, in Cairns, Australia, unseasonably warm temperatures above 30°C in late 2008 are believed to have shortened the EIP of DENV3 in Ae .…”

Section: Potential Factors Contributing To the Increase In Reported D...mentioning

confidence: 99%

“…Annually, a spatial risk model is also built using information such as historical dengue burden, age of buildings, and amount of vegetation in an area to stratify transmission risk and guide resource allocation [ 68 ]. NEA has also adopted novel indices for dengue surveillance to better inform public health operations and channel resources to high-risk areas, such as estimating the effective reproduction number for dengue, which informs disease transmissibility in real time [ 42 ].…”

Section: Evolution Of Singapore’s Dengue Prevention Effortsmentioning

confidence: 99%

Singapore’s 5 decades of dengue prevention and control—Implications for global dengue control

et al. 2023

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This paper summarises the lessons learnt in dengue epidemiology, risk factors, and prevention in Singapore over the last half a century, during which Singapore evolved from a city of 1.9 million people to a highly urban globalised city-state with a population of 5.6 million. Set in a tropical climate, urbanisation among green foliage has created ideal conditions for the proliferation of Aedes aegypti and Aedes albopictus, the mosquito vectors that transmit dengue. A vector control programme, largely for malaria, was initiated as early as 1921, but it was only in 1966 that the Vector Control Unit (VCU) was established to additionally tackle dengue haemorrhagic fever (DHF) that was first documented in the 1960s. Centred on source reduction and public education, and based on research into the bionomics and ecology of the vectors, the programme successfully reduced the Aedes House Index (HI) from 48% in 1966 to <5% in the 1970s. Further enhancement of the programme, including through legislation, suppressed the Aedes HI to around 1% from the 1990s. The current programme is characterised by 4 key features: (i) proactive inter-epidemic surveillance and control that is stepped up during outbreaks; (ii) risk-based prevention and intervention strategies based on advanced data analytics; (iii) coordinated inter-sectoral cooperation between the public, private, and people sectors; and (iv) evidence-based adoption of new tools and strategies. Dengue seroprevalence and force of infection (FOI) among residents have substantially and continuously declined over the 5 decades. This is consistent with the observation that dengue incidence has been delayed to adulthood, with severity highest among the elderly. Paradoxically, the number of reported dengue cases and outbreaks has increased since the 1990s with record-breaking epidemics. We propose that Singapore’s increased vulnerability to outbreaks is due to low levels of immunity in the population, constant introduction of new viral variants, expanding urban centres, and increasing human density. The growing magnitude of reported outbreaks could also be attributed to improved diagnostics and surveillance, which at least partially explains the discord between rising trend in cases and the continuous reduction in dengue seroprevalence. Changing global and local landscapes, including climate change, increasing urbanisation and global physical connectivity are expected to make dengue control even more challenging. The adoption of new vector surveillance and control tools, such as the Gravitrap and Wolbachia technology, is important to impede the growing threat of dengue and other Aedes-borne diseases.

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Fine-scale estimation of effective reproduction numbers for dengue surveillance

Cited by 7 publications

References 53 publications

Associations between Dengue Incidence, Ecological Factors, and Anthropogenic Factors in Singapore

Associations between Dengue Incidence, Ecological Factors, and Anthropogenic Factors in Singapore

Spatial Methods for Inferring Extremes in Dengue Outbreak Risk in Singapore

Singapore’s 5 decades of dengue prevention and control—Implications for global dengue control

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