Mitigating the Risk of Dengue Fever in Nagpur City, India: Insights from a Five-year Retrospective Study
Authors: Mulani Jasmin , Mishra Gyanshankar , Nimgade Shyam , Bahirwar Narendra Mahadeorao , Balasubramanian Radhakrishnan 
Published: July 2024

Objectives:
Dengue is a significant global threat, with millions of infections yearly, primarily transmitted by Aedes mosquitoes. Vector control is crucial as no specific treatment is available, and urbanisation has led to increased susceptibility to the disease. We aimed to study dengue fever’s incidence, mortality, and various determinants in Nagpur, India.

Material and Methods:
This was a retrospective record-based study conducted for the period between January 2018 and December 2022 in Nagpur, India.

Results:
During 2018–2022, 17,306 blood samples were tested for dengue immunoglobulin M antibodies by enzyme-linked immunosorbent assay method with 2470 positive results indicating an overall test positivity of 14.27%. A median of 27 samples was tested monthly (interquartile range [IQR]: 5–178.5) with seven dengue cases (IQR: 1–15) diagnosed per month, yielding a monthly median dengue test positivity rate of 15.3 % (IQR: 6.41–24.28). Median annual dengue incidence rate (per 1,00,000 population) was 20.12 (IQR: 21.46). The median dengue-attributable death yearly was 2 (IQR: 2.25), remaining stable over the study period. The mean annual case fatality rate (CFR) was 0.43% (standard deviation [SD]: 0.34%). During the same period, India’s mean annual dengue incidence rate (per 1,00,000 population) was 1.74 (SD: 0.81), and the mean annual CFR was 0.134 % (SD: 0.042). During the five years, action was taken on 194,698 containers. The median values of environmental factors and public health interventions, as calculated on a monthly basis, were as follows: Container index: 1.15 % (IQR: 0.7–1.98); action taken on containers: 3108.5 (IQR: 2436–4282); house index: 3.02 % (IQR: 2–4.07); guppy fishes introduced: 1736.5 (1005.5–1794.5) and rainfall (mm): 26.05 (1–69.11). The total number of dengue cases, incidence rate, and CFR showed an overall decline in year-wise evaluation. The important determinants identified were as follows: Higher container index, house index, and total blood samples tested for dengue were significant determinants of the total number of dengue cases, and environmental factors such as Aedes density, container index, and house index were significant determinants of dengue-related mortality. Introducing guppy fishes and taking action on containers successfully arrested the absolute number of dengue deaths. The container index, house index, and rainfall were significant determinants of Aedes’ density.

Conclusion:
Our study emphasises the effectiveness of public health interventions in reducing the incidence and fatality rate of dengue fever in Nagpur City over the past five years, particularly through introducing guppy fish and container management. Stagnant water around households has been identified as a significant risk factor for dengue transmission. Prevention strategies must prioritise tackling this issue, with enhanced monitoring during the wet season, and encourage community members to take personal responsibility for eliminating stagnant water sources in their households.