RÉSUMÉ
Background & objectives: Dengue virus (DENV) causes outbreaks and sporadic cases in tropical and subtropical countries. Documenting intricacies of DEN outbreaks is important for future interventions. The objective of this study was to report clinical, laboratory and epidemiological features of DEN outbreaks reported in different districts of Central India in 2016. Methods: In 2016, outbreaks (n=4) suspected of DEN were investigated by rapid response team. Door-to-door fever and entomological surveys were conducted. Blood samples were collected and tested using NS1 or IgM ELISA; real-time reverse transcription-polymerase chain reaction was done to identify serotypes of DEN virus (DENV). NS1-positive samples were tested for the presence of IgG by ELISA. Clinical and demographic data were collected and analyzed. Results: Outbreaks occurred in both urban and rural areas in monsoon season and Aedes aegypti was identified as the vector. Fever, chills, headache and myalgia were the major symptoms; no fatality was recorded. Of the 268 DEN suspects, 135 (50.4%) were found serologically positive. DEN positivity was higher (n=75; 55.56%) among males and in the age group of 16-45 yr (n=78; 57.8%). DENV 3 followed by DENV 2 were detected as the major responsible serotypes. High attack rates (up to 38/1000) and low cumulative IgG prevalence (14.9%) were recorded in rural areas. Interpretation & conclusions: Our study showed that DENV 3 was the major serotype responsible for outbreaks that occurred in monsoon. High attack rates and lower number of secondary infections in rural areas indicated that DENV is emerging in rural parts of Central India. Early diagnosis at local level and timely intervention by mosquito control activities are needed to avoid such outbreaks in future.
RÉSUMÉ
Purpose: Dengue viruses (DENVs), the causative agents of dengue (DEN), are classified into four serotypes and several genotypes. Identifying circulating serotypes and genotypes has clinical and epidemiological importance; however, limited information in this regard is available from Central India. This laboratory-based study was done to fill this lacuna. Materials and Methods: The samples collected in the acute phase of illness were subjected to DEN NS1 ELISA, and NS1-positive samples (n = 80) were subjected to serotyping; representative samples from each serotype were sequenced to identify genotypes. Results: Seventy-one (88.75%) samples could be serotyped. All the four DENV serotypes with dominance of DENV-3 (n = 33; 47%) were detected. DENV-4 was detected after a gap of 3 years. Cases with multiple DENV serotype infection were identified. Genotyping showed that DENV-1 belonging to genotype III, DENV-2 cosmopolitan (IV), DENV-3 genotype III lineage C and DENV-4 genotype I were in circulation in the year 2016. Conclusion: Our study documents the molecular characteristics of DENV circulating in the area. Detection of heterologous DENV serotype with dominance of DENV-3 emphasises the need for regular molecular monitoring.