Emergence of dengue in Nepal

Genomic sequencing and neutralizing serological profiles during acute dengue infection: A 2017 cohort study in Nepal

Dengue virus (DENV) is a mosquito-borne flavivirus that poses a threat to nearly 50% of the global population. DENV has been endemic in Nepal since 2006; however, little is known about how DENV is evolving or the prevalence of anti-DENV immunity within the Nepalese population. To begin to address these gaps, we performed a serologic and genetic study of 49 patients from across Nepal who presented at central hospitals during the 2017 dengue season with suspected DENV infection. Of the 49 subjects assessed, 21 (43%) were positive for DENV NS1 antigen; of these; 5 were also anti-DENV IgM + IgG + ; 7 were DENV IgM + IgG - , 2 were IgM - IgG + , and 7 were IgM - IgG - by specific ELISAs. Seven of the 21 NS1+ sera were RNA+ by RT-PCR (six DENV2, one DENV3), suggesting that DENV2 was the dominant serotype in our cohort. Whole-genome sequencing of two DENV2 isolates showed similarity with strains circulating in Singapore in 2016, and the envelope genes were also similar to strains circulating in India in 2017. DENV-neutralizing antibodies (nAbs) were present in 31 of 47 sera tested (66%); among these, 20, 24, 26, and 12 sera contained nAbs against DENV1, 2, 3, and 4 serotypes, respectively. Serology analysis suggested that 12 (26%) and 19 (40%) of the 49 subjects were experiencing primary and secondary DENV infections, respectively. Collectively, our results provide evidence for current and/or past exposure to multiple DENV serotypes in our cohort, and the RNA analyses further indicate that DENV2 was the likely dominant serotype circulating in Nepal in 2017. These data suggest that expanded local surveillance of circulating DENV genotypes and population immunity will be important to effectively manage and mitigate future dengue outbreaks in Nepal.

Dengue virus infection during window period of consecutive outbreaks in Nepal and assessment of clinical parameters

Nepal is an endemic country for dengue infection with rolling of every 3 year's clear cyclic outbreaks with exponential growth since 2019 outbreak and the virus gearing towards the non-foci temperate hill regions. However, the information regarding circulating serotype and genotype is not frequent. This research discusses on the clinical features, diagnosis, epidemiology, circulating serotype and genotype among 61 dengue suspected cases from different hospitals of Nepal during the window period 2017-2018 between the two outbreaks of 2016 and 2019. E-gene sequences from PCR positive samples were subjected to phylogenetic analysis under time to most recent common ancestor tree using Markov Chain Monte Carlo (MCMC) and BEAST v2.5.1. Both evolution and genotypes were determined based on the phylogenetic tree. Serotyping by Real-time PCR and Nested PCR showed the co-circulation of all the 3 serotypes of dengue in the year 2017 and only DENV-2 in 2018. Genotype V for DENV-1 and Cosmopolitan Genotype IVa for DENV-2 were detected. The detected Genotype V of DENV-1 in Terai was found close to Indian genotype while Cosmopolitan IVa of DENV-2 found spreading to geographically safe hilly region (now gripped to 9 districts) was close to South-East Asia. The genetic drift of DENV-2 is probably due to climate change and rapid viral evolution which could be a representative model for high altitude shift of the infection. Further, the increased primary infection indicates dengue venturing to new populations. Platelets count together with Aspartate transaminase and Aalanine transaminase could serve as important clinical markers to support clinical diagnosis. The study will support future dengue virology and epidemiology in Nepal.

Admitted Cases of Dengue Fever among Dengue Positive Cases in a Tertiary Care Hospital: A Descriptive Cross-sectional Study

INTRODUCTION

Dengue fever, a mosquito-borne disease, is one of the emerging tropical diseases that appear primarily in rainy seasons. The number of dengue cases was increased in recent years in Nepal. Chitwan is one of the risky areas of dengue. This aim of the study is to find out the prevalence of hospital admission among the dengue positive cases.

METHODS

The descriptive cross-sectional study was carried out among 323 serologically confirmed dengue fever positive patient admitted in Medicine Inpatients Department of Chitwan Medical College Teaching Hospital. Ethical approval was taken from the Institutional Review Committee (Reference number. 076/077-121 dated August 30, 2019). Data were collected from 1st September 2019 to 31st December 2019 using a structured interview schedule and record review. Convenience sampling was done. Data was analysed using Statistical Package for Social Sciences version 11. Point estimate at 95% Confidence Interval was calculated, with frequency and percentage.

RESULTS

Among 1206 patient with dengue fever, 323 (26.78%) (24.29-29.27 at 95% confidence Interval) were admitted in the tertiary care hospital. Study findings revealed that out of 323 admitted patients with dengue fever, 182 (56.3%) patients were between 20-40 years of age and 179 (55.4%) were males. The highest number of patients were admitted in the months of September 192 (59.4%) and October 101 (31.2%).

CONCLUSIONS

Admission rate among dengue positive cases are comparable to other studies of the similar settings. Dengue fever is common among community people especially in young adult and males. Hence, screening of dengue fever in febrile illness is necessary for the early diagnosis and prompt treatment.

Epidemiology and challenges of dengue surveillance in the WHO South-East Asia Region

Dengue poses a significant health and economic burden in the WHO South-East Asia Region. Approaches for control need to be aligned with current knowledge on the epidemiology of dengue in the region. Such knowledge will ensure improved targeting of interventions to reduce dengue incidence and its socioeconomic impact. This review was undertaken to describe the contemporary epidemiology of dengue and critically analyse the existing surveillance strategies in the region. Over recent decades, dengue incidence has continued to increase with geographical expansion. The region has now become hyper-endemic for multiple dengue virus serotypes/genotypes. Every epidemic cycle was associated with a change of predominant serotype/genotype and this was often associated with severe disease with intense transmission. Classical larval indices are widely used in vector surveillance and adult mosquito samplings are not implemented as a part of routine surveillance. Further, there is a lack of integration of entomological and disease surveillance systems, often leading to inaction or delays in dengue prevention and control. Disease surveillance does not capture all cases, resulting in under-reporting, and has thus failed to adequately represent the true burden of disease in the region. Possible solutions include incorporating adult mosquito sampling into routine vector surveillance, the establishment of laboratory-based sentinel surveillance, integrated vector and dengue disease surveillance and climate-based early warning systems using available technologies like mobile apps.

Molecular phylogeny and distribution of dengue virus serotypes circulating in Nepal in 2017

Dengue virus (DENV) infection is endemic in Nepal. Although infection rates are reported annually, little information is available about the circulating viral serotypes and genotypes. Here, we report the results of a multicentre cross-sectional study of DENV serotypes and genotypes sampled from individuals with suspected DENV infection in Nepal in 2017. Of the 50 patients sampled, 40 were serologically positive for DENV NS1, 29 for anti-DENV IgM, 21 for anti-DENV IgG and 14 were positive by qRT-PCR. The three serotypes DENV-1, 2 and 3 were detected and there was no DENV-4. Positive samples from serotyping were subjected to PCR amplification by envelope (E) gene specific primer and subsequent bidirectional sequencing of 5 samples. A time to most recent common ancestor phylogenetic tree was constructed from the new sequences obtained here together with historical DENV-1 and DENV-2 E gene sequences. The DENV-1 isolates (n = 2) from Nepalese individuals were closely related to Indian genotype V, whereas DENV-2 isolates (n = 3) belonged to Cosmopolitan genotype IVa, which is closely related to Indonesian isolates. Historical DENV isolates obtained between 2004 and 2013 clustered with Cosmopolitan IVb, Cosmopolitan IVa, and Asian II genotypes. All Nepalese isolates had different lineages with distinct ancestries. With the exception of isolates obtained in 2004, all other previously published isolates had ancestry to geographically distant part of the world. Molecular analysis revealed dengue epidemics to be comprised of different genotypes of serotype 1 and 2 raising concerns on potential role of different genotypes causing Dengue hemorrhagic fever. Also, our result indicated spread of DENV-2 in non-endemic area such as hilly region of Nepal which was considered to be free of dengue due to high altitude and cold weather.

Molecular epidemiology of dengue fever outbreaks in Bhutan, 2016-2017

Dengue continues to pose a significant public health problem in tropical and subtropical countries. In Bhutan, first outbreak of dengue fever (DF) was reported in 2004 in a southern border town, followed by sporadic cases over the years. In this study, we analysed DF outbreaks that occurred in 3 different places during the years 2016 and 2017. A total of 533 cases in 2016 and 163 in 2017 were suspected of having of DF, where young adults were mostly affected. A total of 240 acute serum specimens collected and analyzed for serotype by nested RT-PCR revealed predominance of serotypes 1 and 2 (DENV-1 and 2). Phylogenetic analysis using envelope gene for both the serotypes demonstrated cosmopolitan genotype which were closely related to strains from India, indicating that they were probably imported from the neighboring country over the past few years.

Endemicity of DENV in some places of southern Bhutan has been established previously. In this study, we analysed outbreaks of DF that occurred in 3 places over a period of 2 years, 1 of which was previously not known to be endemic to DENV. Serum specimens collected from patients suspected of having DF were analyzed in the Royal Centre for Disease Control (RCDC) in Bhutan and in Armed Forces Research Institute of Medical Sciences (AFRIMS), Thailand. DENV-1 and 2 were established as the causes of the outbreaks, also indicating that serotypes of DENV circulating in the country over the past years have remained the same. Our analyses reveal that the current DENV-1and DENV-2 in Bhutan probably originated from India, Bhutan’s closest neighboring country.

The Dengue virus in Nepal: gaps in diagnosis and surveillance

Background

The introduction of the dengue virus (DENV) in Nepal is recent, first reports date back to 2004 from a Japanese traveller and limited information is available about DENV infection in the Nepali population. Within a decade after the first DENV detection, it is now endemic in multiple districts of Nepal with approximately 11.2 million people residing in the Terai belt being at risk of DENV infection. Sporadic cases of DENV infection have been reported every year for the past decade during the monsoon season, mainly in the Terai region.

Methods

Medline/Embase/Cochrane databases were reviewed for reports on the burden of dengue infection, diagnostic methods, and national surveillance.

Results

Four outbreaks were reported since 2004 including the diagnosis of all serotypes in 2006 and predominance of a single serotype in 2010 (DENV-1), 2013 (DENV-2), and 2016 (DENV-1). The clinical diagnoses showed a predominance of dengue fever while 4/917 (0.4%), 8/642 (1.2%) and 8/1615 (0.4%) dengue haemorrhagic fever/dengue shock syndrome cases were identified during the outbreaks in 2010, 2013 and 2016, respectively. The number of cases reported in males was significantly higher (67.4%) than in females. Disease occurrence was primarily found in the Terai region until 2010 and was increasingly detected in the Hilly region in 2016.

Conclusion

In Nepal currently weak diagnostic facilities, very limited research on mosquitoes vectors, and poor surveillance of dengue leading to inappropriate detection and control of DENV. We surmise that improved basic research and epidemiological training courses for local scientists and laboratory personal at national and international level will help better understand the evolution and distribution of DENV transmission and its eventual control.

Profile of the 2016 dengue outbreak in Nepal

OBJECTIVE

The objective of this study was to obtain clinical, virological and demographic data detailing the 2016 dengue outbreak in Nepal.

RESULTS

Dengue disease was first reported in Nepal in 2004 and several major outbreaks have occurred since then, with a significant impact on public health. An outbreak of dengue fever occurred in Nepal during June to November 2016, with a peak number of cases reported in September. 1473 patients with laboratory confirmed DENV infections visited or were admitted to hospitals during this period. The most common clinical symptoms included fever, headache, joint pain and thrombocytopenia. Serotyping of 75 serum samples from patients having fever for less than 4 days was carried out with a dengue virus (DENV) serotype-specific RT-PCR strategy. Our results indicate that the dengue outbreak in Nepal during 2016 was caused predominantly, if not exclusively, by DENV-1, representing a shift in the prevailing serotype from DENV-2, the dominant serotype characterizing the 2013 dengue epidemic in Nepal. Hopefully, this report will assist Nepalese public health agencies in developing improved dengue-related programs including mosquito-vector control, DENV surveillance, and diagnosis and treatment of dengue fever patients, in order to reduce the impact of future dengue epidemics.