Maiden outbreaks of dengue virus 1 genotype III in rural central India

Abstract

Dengue is regarded as the most important arboviral disease. Although sporadic cases have been reported, serotypes responsible for outbreaks have not been identified from central India over the last 20 years. We investigated two outbreaks of febrile illness, in August and November 2012, from Korea district (Chhattisgarh) and Narsinghpur district (Madhya Pradesh), respectively. Fever and entomological surveys were conducted in the affected regions. Molecular and serological tests were conducted on collected serum samples. Dengue-specific amplicons were sequenced and phylogenetic analyses were performed. In Korea and Narsinghpur districts 37·3% and 59% of cases were positive, respectively, for dengue infection, with adults being the worst affected. RT-PCR confirmed dengue virus serotype 1 genotype III as the aetiology. Ninety-six percent of infections were primary. This is the first time that dengue virus 1 outbreaks have been documented from central India. Introduction of the virus into the population and a conducive mosquitogenic environment favouring increased vector density caused the outbreak. Timely diagnosis and strengthening vector control measures are essential to avoid future outbreaks.

Fig. 1.

(a) Map of India showing (b) Madhya Pradesh and Chhattisgarh. (c) The outbreak districts of Korea and Narsinghpur are indicated by grey shading (map not to scale).

Fig. 2

[colour online]. Graph showing the curve of cases and Breteau index (BI). Cases gradually declined as the BI decreased to <5).

Fig. 3.

The maximum-likelihood phylogenetic tree with Kimura two-parameter corrections using the E/NS1 gene junction of DENV-1 detected from Churcha, indicated by ▲; DENV-1 from Narshinghpur district indicated by ●. The tree was generated using 23 sequences downloaded from the Genbank database and MEGA v. 5 software. The tree was validated using 1000 bootstraps. The analyses demonstrated that DENV-1 belongs to genotype III.