Circulation of dengue serotypes in the Union Territory of Dadra & Nagar Haveli (India)

Mapping the distribution and trends of co-circulating dengue virus serotypes in Odisha, India: A retrospective facility-based analysis

Background Dengue, caused by mosquito bite, is an emerging disease of international concern. Evidence regarding the prevalent dengue serotypes is scarce, but essential for its management during the outbreaks. Hence, we mapped the distribution and trends of currently prevalent dengue virus (DENV) serotypes in Odisha. Methods We conducted a facility-based retrospective study from referral samples sent for the diagnosis/confirmation of dengue in 2018. The samples were serologically tested for enzyme-linked immunosorbent assay (ELISA) IgM antibody and NS1. Only NS1-positive samples were chosen for sero-typing. A pool of 8-10 NS1-positive samples were analysed for district-wise serotypes. Ribonucleic acid extraction and nested polymerase chain reaction (PCR) was done from NS1-positive samples. The PCR products were then subjected to gel electrophoresis. Results A total of 2892 samples were screened for dengue virus across various districts of Odisha where 763 samples were found to be NS1-positive. Thirteen of 18 districts covering all topographies of Odisha predominantly had DENV2 serotype. Only few districts such as Balangir, Kalahandi and Rayagada had mixed serotypes. Conclusion Although DENV2 is predominantly prevalent, mixed serotypes too exist in Odisha. Evidence based on variations of dengue serotypes across topographies, seasons, gender and age groups may support public health efforts in preventing the disease.

Characterizing dengue transmission in rural areas: A systematic review

Dengue has historically been considered an urban disease associated with dense human populations and the built environment. Recently, studies suggest increasing dengue virus (DENV) transmission in rural populations. It is unclear whether these reports reflect recent spread into rural areas or ongoing transmission that was previously unnoticed, and what mechanisms are driving this rural transmission. We conducted a systematic review to synthesize research on dengue in rural areas and apply this knowledge to summarize aspects of rurality used in current epidemiological studies of DENV transmission given changing and mixed environments. We described how authors defined rurality and how they defined mechanisms for rural dengue transmission. We systematically searched PubMed, Web of Science, and Embase for articles evaluating dengue prevalence or cumulative incidence in rural areas. A total of 106 articles published between 1958 and 2021 met our inclusion criteria. Overall, 56% (n = 22) of the 48 estimates that compared urban and rural settings reported rural dengue incidence as being as high or higher than in urban locations. In some rural areas, the force of infection appears to be increasing over time, as measured by increasing seroprevalence in children and thus likely decreasing age of first infection, suggesting that rural dengue transmission may be a relatively recent phenomenon. Authors characterized rural locations by many different factors, including population density and size, environmental and land use characteristics, and by comparing their context to urban areas. Hypothesized mechanisms for rural dengue transmission included travel, population size, urban infrastructure, vector and environmental factors, among other mechanisms. Strengthening our understanding of the relationship between rurality and dengue will require a more nuanced definition of rurality from the perspective of DENV transmission. Future studies should focus on characterizing details of study locations based on their environmental features, exposure histories, and movement dynamics to identify characteristics that may influence dengue transmission.