Epidemiological characteristics and determinants of dengue transmission during epidemic and non-epidemic years in Fortaleza, Brazil: 2011-2015

Abstract

BackgroundAfter being eliminated during the 1950s, dengue reemerged in Brazil in the 1980s. Since then, incidence of the disease has increased, as serotypes move within and between cities. The co-circulation of multiple serotypes contributes to cycles of epidemic and interepidemic years, and a seasonal pattern of transmission is observed annually. Little is known regarding possible differences in the epidemiology of dengue under epidemic and interepidemic scenarios. This study addresses this gap and aims to assess the epidemiological characteristics and determinants of epidemic and interepidemic dengue transmission, utilizing data from the 5th largest city in Brazil (Fortaleza), at fine spatial and temporal scales.Methods/Principal findingsLongitudinal models of monthly rates of confirmed dengue cases were used to estimate the differential contribution of contextual factors to dengue transmission in Fortaleza between 2011 and 2015. Models were stratified by annual climatological schedules and periods of interepidemic and epidemic transmission, controlling for social, economic, structural, entomological, and environmental factors. Results revealed distinct seasonal patterns between interepidemic and epidemic years, with persistent transmission after June in interepidemic years. Dengue was strongly associated with violence across strata, and with poverty and irregular garbage collection during periods of low transmission, but not with other indicators of public service provision or structural deprivation. Scrapyards and sites associated with tire storage were linked to incidence differentially between seasons, with the strongest associations during transitional precipitation periods. Hierarchical clustering analysis suggests that the dengue burden concentrates in the southern periphery of the city, particularly during periods of minimal transmission.Conclusions/SignificanceOur findings have direct programmatic implications. Vector control operations must be sustained after June even in non-epidemic years. More specifically, scrapyards and sites associated with tires (strongly associated with incidence during periods of minimal transmission), require sustained entomological surveillance, particularly during interepidemic intervals and in the urban periphery. Intersectoral collaborations that address urban violence are critical for facilitating the regular activities of vector control agents.

Population mobility and dengue fever transmission in a major city in Southeastern Brazil, 2007-2015

“…Residence in apartments was also a variable correlated with income in Campinas, as verticalization occurs more expressively in the city center, which is also the region with the highest concentration of more affluent people. This result corroborates previous findings of the role of income in DENV epidemics [26,48–53].…”

“…Regarding Strategic Points, we found that the addition of one SP in an area tended to increase the dengue incidence rate by 3%, a result consistent with previous findings [26,27]. Although there are clear guidelines on how to monitor SPs, including mandatory inspection visits every fifteen days [24], limited financial resources, skilled professionals or even violence in an area can affect the regularity of these visits [26,54].…”

“…We also gathered data on Strategic Points (SPs), comprising locations such as junkyards, tire repair shops, deposits of recyclable materials, etc. They are essential for understanding dengue occurrence as these areas present huge potential to accumulate Aedes breeding sites [24,26,27]. Examples are shown in Fig 2.…”

“…The accumulated precipitation was calculated per epidemiological week for each OD unit. After an assessment of previous works [17,26,30–32], we tested different lags: 2 weeks, 4 weeks (1 month), 8 weeks (2 months), and 12 weeks (3 months). This lag aimed to cover the expected time necessary for the precipitating water to pool, and for the entire cycle of transmission (from oviposition to a confirmed dengue case) to take place [17,33,34].…”

Solid Wastes Provide Breeding Sites, Burrows, and Food for Biological Disease Vectors, and Urban Zoonotic Reservoirs: A Call to Action for Solutions-Based Research

“…Vector-borne diseases such as dengue-transmitted by container breeding Aedes spp.-threaten about half a billion people in densely populated areas (42). One very important mosquito vector, Aedes aegypti, which spreads dengue, Zika, chikungunya, and yellow fever, prefers to breed in man-made containers (43,44), such as recyclable plastic containers, tires, and trash. The 2,050 projections of over 6 billion people living in urban areas (45) suggest an impending increase in the risk of infectious disease transmission.…”