Role of a Surveillance System in the Management of an Outbreak of Dengue in the Mid Hills of Himachal Pradesh, India

Abstract

Introduction: Surveillance systems are instrumental in not only eliciting the impending outbreaks but also for initiation of public health action. Integrated Disease Surveillance Programme (IDSP) of India guides in the clinical and laboratory diagnosis of vector borne diseases such as Dengue and its management. Aim: To assess any impending outbreak of Dengue in the region, by using IDSP surveillance data and to assess the need based mitigation measures. Materials and Methods: The routine IDSP surveillance of June 2015 highlighted an impending outbreak of Dengue in Solan district of Himachal Pradesh, India. Spot map was prepared for epidemiological linkage of the sporadic cases being reported. Moreover the retrospective epidemiologic IDSP surveillance data was analysed for finding out any cases of Dengue reported in the past. Clinical case definition of Dengue, formulated by IDSP was adopted. Diagnostic facility was set up. Entomological surveillance was used to calculate House Index, Container Index, Breteau Index. Aedes ageypti mosquito was identified by laboratory techniques. Mitigation activities like sanitation and cleanliness drive, fogging, inter-sectoral meetings and coordination were initiated. Daily surveillance was initiated and data was analysed in Microsoft Office Excel 2010 and Epi Info software version 7.2.0.1. The value of p<0.05 was considered as significant. Results: Based upon data analysis, outbreak of Dengue was declared on 7th September, 2015. A total of 686 probable cases were positive by rapid diagnostic/card tests whereas 57 and 109 patients were positive by NS1Ag and IgM tests. The relation of Dengue with respect to age and sex of the patients was found statistically non-significant with p-values of 2.01 and 3.20 respectively. House Index was higher (37.5%) in the industry dominated Nalagarh region. Genus Aedes was identified in three out of 12 mosquito specimens with the help of available mosquito key. Other specimens were beyond recognition since these were deformed either during collection or in the process of rearing and thus could not be identified. A 7.5% of total houses screened were covered under sanitation drive. Pyrethrum fogging was done in 1397 houses. Conclusion: The study shows the utility of IDSP system feedback in management of Dengue by formulated clinical case definitions and setting up of diagnostic facility for prompt identification of cases and early curtailment of outbreak.

Keywords

• Entomologic surveillance
• Identification
• Mosquito key