The Spread of Dengue in an Endemic Urban Milieu–The Case of Delhi, India

Abstract

BackgroundDengue is a major international public health concern, one of the most important arthropod-borne diseases. More than 3.5 billion people are at risk of dengue infection and there are an estimated 390 million dengue infections annually. This prolific increase has been connected to societal changes such as population growth and increasing urbanization generating intense agglomeration leading to proliferation of synanthropic mosquito species. Quantifying the spatio-temporal epidemiology of dengue in large cities within the context of a Geographic Information System is a first step in the identification of socio-economic risk factors.Methodology/Principal FindingsThis Project has been approved by the ethical committee of Institut Pasteur. Data has been anonymized and de-identified prior to geolocalisation and analysis. A GIS was developed for Delhi, enabling typological characterization of the urban environment. Dengue cases identified in the Delhi surveillance system from 2008 to 2010 were collated, localised and embedded within this GIS. The spatio-temporal distribution of dengue cases and extent of clustering were analyzed. Increasing distance from the forest in Delhi reduced the risk of occurrence of a dengue case. Proximity to a hospital did not increase risk of a notified dengue case. Overall, there was high heterogeneity in incidence rate within areas with the same socio-economical profiles and substantial inter-annual variability. Dengue affected the poorest areas with high density of humans, but rich areas were also found to be infected, potentially because of their central location with respect to the daily mobility network of Delhi. Dengue cases were highly clustered in space and there was a strong relationship between the time of introduction of the virus and subsequent cluster size. At a larger scale, earlier introduction predicted the total number of cases.Conclusions/SignificanceDENV epidemiology within Delhi has a forest fire signature. The stochastic nature of this invasion process likely smothers any detectable socio-economic risk factors. However, the significant finding that the size of the dengue case cluster depends on the timing of its emergence emphasizes the need for early case detection and implementation of effective mosquito control. A better understanding of the role of population mobility in contributing to dengue risk could also help focus control on areas at particular risk of dengue virus importation.

Structure in the variability of the basic reproductive number (R0) for Zika epidemics in the Pacific islands

“…This exposed fraction could be the result of spatial heterogeneity and high clustering of cases and transmission, as observed for dengue. The small dispersal of the mosquito and the limited population inter-mingling likely leads to considerable spatial variation in the extent of exposure to the virus and pockets of refugia in Tahiti as elsewhere (Telle et al, 2016). For instance, previous dengue infection rates in French Polynesia display large spatial variations even within islands (Daudens et al, 2009).…”

Dengue seropositivity in a randomly selected sample from Yucatan analyzed in the context of dengue cases reported between 1996 and 2006

“…It is not late for the Mexican health agencies to improve the dengue surveillance system, including the implementation of periodic serosurveys in endemic regions as a part of a complete, holistic approach, in order to not only predict the occurrence of an outbreak, but also to evaluate the impact of DF and DHF programs. [14][15][16] …”

Avaliação Espacial da Dengue na Área Urbana de Itu - São Paulo

“…Conhecida internacionalmente pelo Código Internacional de Doença (CID10) como A90, o conhecimento da distribuição geográfica dos casos de dengue nos espaços urbanos é essencial para o entendimento da mortalidade causadas pela patologia e auxiliar as políticas de gestão e avaliação do impacto da doença sobre a população (GUZMAN et al, 2010;TELLE, 2015).…”

“…Estima-se que entre 70 a 500 milhões de pessoas são infectadas pelo vírus da dengue a cada ano, em mais de cem países, sendo que a maioria dos casos ocorre em áreas urbanas (SIMMONS et al, 2012;BHATT et al, 2013;GONÇALVES et al, 2015;TELLE, 2015). As taxas de incidência são maiores na América Latina e Ásia, enquanto a África possui as informações mais escassas sobre a patologia.…”

“…As taxas de incidência são maiores na América Latina e Ásia, enquanto a África possui as informações mais escassas sobre a patologia. Na Índia, as maiores prevalências foram detectadas em áreas urbanizadas e com predomínio de infecção em homens entre 26 e 59 anos (BHATT et al, 2013;TELLE, 2015).…”