Re-emergence of dengue virus serotype 2 strains in the 2013 outbreak in Nepal

Abstract

Background & objectives:Epidemiological interventions and mosquito control are the available measures for dengue control. The former approach uses serotype and genetic information on the circulating virus strains. Dengue has been frequently reported from Nepal, but this information is mostly lacking. The present study was done to generate a comprehensive clinical and virological picture of a dengue outbreak in Nepal during 2013.Methods:A hospital-based study involving patients from five districts of Nepal was carried out. Demographic information, clinical details and dengue serological status were obtained. Viral RNA was characterized at the molecular level by reverse-transcription polymerase chain reaction (RT-PCR), nucleotide sequencing and phylogenetic analysis.Results:From among the 2340 laboratory-confirmed dengue cases during the study period, 198 patients consented for the study. Clinically they had fever (100%), headache (59.1%), rashes (18.2%), retro-orbital pain (30.3%), vomiting (15.1%), joint pain (28.8%) and thrombocytopenia (74.3%). Fifteen (7.5%) of them had mucosal bleeding manifestations, and the rest were uncomplicated dengue fever. The patients were mostly adults with a mean age of 45.75 ± 38.61 yr. Of the 52 acute serum samples tested, 15 were positive in RT-PCR. The causative virus was identified as DENV serotype 2 belonging to the Cosmopolitan genotype.Interpretations & conclusions:We report here the involvement of DENV serotype 2 in an outbreak in Nepal in 2013. Earlier outbreaks in the region in 2010 were attributed to serotype 1 virus. As serotype shifts are frequently associated with secondary infections and severe disease, there is a need for enhancing surveillance especially in the monsoon and post-monsoon periods to prevent large-scale, severe dengue outbreaks in the region.

Dengue periodic outbreaks and epidemiological trends in Nepal

“…The study for 11 years with regards to the gender based analysis showed that the male population was more likely to have infection than female at the mean ratio of 2:1, which is in agreement to the past study done by Gupta et al [ 25 ]. One can assume that compared to women who are generally confined within household works the male population is mostly involved in outdoor work activities for livelihood which makes them more likely exposed to Aedes spp.…”

“…Annual seasonal variation trends of the dengue occurrence shows, infections appear abruptly in July, just after the start of the rainy season and cases peaks in August and September, which are considered to be the months with the most favorable climate for mosquitoes breading [ 24 , 25 ]. Similar seasonal response was found in a study conducted in China and Philippines [ 26 , 27 ].…”

Emergence of genotype Cosmopolitan of dengue virus type 2 and genotype III of dengue virus type 3 in Thailand

“…Previously, DENV-2 genotype Cosmopolitan was detected in Maritime South East Asia (Indonesia, Malaysia, Singapore, and Philippines) [ 50 – 54 ] and South Asia (India, Bangladesh, Nepal, Pakistan, and Sri Lanka) [ 5 , 6 , 55 , 56 ]. The phylogenetic tree of the envelope genes of DENV-2 Thailand strains collected from 1964–2017 confirmed the presence of two genotypes in separate monophyletic clusters ( Fig 2 ).…”

Dengue virus infection in a French traveller to the hilly region of Nepal in 2015: a case report

“…A. aegypti was first reported in Kathmandu in 2010 and the vectors may have now established populations up in the mountains [ 12 ]. Serotype and genotype shifts have been reported based on sequencing of specific viral regions [ 15 ]. In-depth molecular study of the virus found in the hill region of Nepal might give insights into the climatic shift of dengue disease.…”