Sentinel versus passive surveillance for measuring changes in dengue incidence: Evidence from three concurrent surveillance systems in Iquitos, Peru

Abstract

34Monitoring changes in infectious disease incidence is fundamental to outbreak detection and 35 response, intervention outcome monitoring, and identifying environmental correlates of 36 transmission. In the case of dengue, little is known about how consistently surveillance data track 37 disease burden in a population over time. Here we use four years of monthly dengue incidence 38 data from three sources -population-based ('passive') surveillance including suspected cases, 39 'sentinel' surveillance with 100% laboratory confirmation and complete reporting, and door-to-40 door ('cohort') surveillance conducted three times per week -in Iquitos, Peru, to quantify their 41 relative consistency and timeliness. Data consistency was evaluated using annual and monthly 42 expansion factors (EFs) as cohort incidence divided by incidence in each surveillance system, to 43 assess their reliability for estimating disease burden (annual) and monitoring disease trends 44 (monthly). Annually, passive surveillance data more closely estimated cohort incidence (average 45 annual EF=5) than did data from sentinel surveillance (average annual EF=19). Monthly passive 46 surveillance data generally were more consistent (ratio of sentinel/passive EF standard 47 deviations=2.2) but overestimated incidence in 26% (11/43) of months, most often during the 48 second half of the annual high season as dengue incidence typically wanes from its annual peak. 49Increases in sentinel surveillance incidence were correlated temporally (correlation coefficient = 50 0.86) with increases in the cohort, while passive surveillance data were significantly correlated at 51 both zero-lag and a one-month lag (0.63 and 0.44, respectively). Together these results suggest 52 that, rather than relying on a single data stream, a clearer picture of changes in infectious disease 53 incidence might be achieved by combining the timeliness of sentinel surveillance with the 54 representativeness of passive surveillance.Infectious disease surveillance in developing countries is often challenged by limited 57 public health resources, insufficient laboratory capacity, and incomplete reporting [1]. In order to 58 obtain high-quality data in the face of these and other challenges, the World Health Organization 59 (WHO) has recommended sentinel surveillance for many infectious diseases [2,3]. In sentinel 60 surveillance systems, resources are focused on collecting complete, timely data from a subset of 61 healthcare facilities or laboratories [4], thus requiring fewer resources than would be needed to 62 actively collect the same quality of data from all facilities (population-based active surveillance). 63 Passive surveillance systems, in which data collection is dependent on reporting by healthcare 64 facilities, are representative by virtue of being population-based, but are also subject to under-65 detection and underreporting [5]. The goal of this study is to evaluate the public health utility of 66 sentinel surveillance compared to passive surveillance for measu...

Disease Burden of Dengue in the Philippines: Adjusting for Underreporting by Comparing Active and Passive Dengue Surveillance in Punta Princesa, Cebu City

“…The results support previous evidence that reporting rates of dengue episodes may vary substantially over time21,44,45 and among locations. These variations may be explained by differential access to health care and health-care quality, providers' attention to dengue, variation in DENV serotypes, patients' health-seeking behavior, and mosquito population densities, among other factors.…”

“…Evidence from Puerto Rico and Brazil, both of which have a well-funded surveillance system, suggests that even fatal DENV infections may be underreported 42,43. These findings, together with the variability in reporting rates shown in previous studies,21,44,45 underscore the need to improve understanding of the relation between passive surveillance and accurate reporting of dengue cases.…”

The burden of dengue fever and chikungunya in southern coastal Ecuador: Epidemiology, clinical presentation, and phylogenetics from the first two years of a prospective study

“…In a pediatric cohort in Nicaragua, investigators detected 21.3 times more DENV infections than were reported to the national surveillance system 57 . A study in Peru compared passive surveillance of DENV to a cohort study and sentinel clinic surveillance, and found five times more DENV infections in the cohort and 19 times more DENV infections through sentinel clinic surveillance 25 . They found that both sentinel and cohort surveillance methods detected an increase in DENV infections more rapidly than passive surveillance methods.…”

“…This is especially important in places and in subgroups with low healthcare seeking behavior, which result in underreporting and continued disease transmission. 18,71 Enhanced surveillance systems have been shown to detect an increase in infections earlier than passive surveillance systems, 25 providing a warning of an escalating outbreak. These data are currently being used to parameterize and calibrate local epidemic forecast models.…”

“…There have been prior enhanced surveillance studies to estimate the burden of dengue fever in Asia 21 ‒ 24 and Latin America 25 ‒ 31 , with study designs ranging from pediatric to adult cohorts, tracking of school-based absentees, use of sentinel clinics, and community-based cluster investigations. In general, these studies found that enhanced surveillance methods identified a greater number of DENV infections, especially mild and inapparent infections, compared to traditional passive surveillance systems.…”