Genetic characterization of dengue virus types 1 and 2 in India, with emphasis on the viruses circulating in Karnataka

Prevalence of Different Dengue Serotypes in Northern India, 2021-2022: A Tertiary Care Hospital-Based Study

Dengue fever is a substantial emerging and reemerging arboviral virus in tropical and subtropical areas that seriously threatens public health worldwide. India is experiencing rising dengue epidemics in urban and rural regions linked to all four serotypes. The objective is to examine the serotypes and genotypes of the circulating dengue virus (DENV) at a tertiary care center in eastern Uttar Pradesh, India, from 2020 to 2021. This retrospective cross-sectional observational study involved dengue patients from January 2021 to December 2022. The genetic analysis of the circulating DENV was conducted by amplifying the partial CprM (511-bp) gene using nested reverse transcriptase polymerase chain reaction (RT-PCR), followed by sequencing. Only those positive for NS1 antigen (n = 581) were included in the study. A total of 204 cases (35.1%) were seropositive, with 96 cases (37.4%) out of 257 in 2021 and 108 cases (33.3%) out of 324 in 2022. With 119 cases (58.3%), men were most affected. The nested RT-PCR for dengue revealed three DENV-1 to DENV-3, except for DENV-4. DENV-2 and DENV-3 were the most predominant serotypes, with 98 (48%) and 94 (46%) cases, respectively. Conversely, DENV-1 was the least prevalent with cases 3 (1.6%). Unfortunately, 35 (17.2%) of the 204 cases died. DENV-2 had the highest mortality rate, with 23 deaths (65.7%). In cases with DENV-3, nine (25.7%) died. This study revealed regional disparities in DENV serotype prevalence in India. If regional differences in the most common serotypes and genotypes are identified early in the season, molecular surveillance may predict major dengue outbreaks and severity.

Co-circulation of all the four Dengue virus serotypes during 2018-2019: first report from Eastern Uttar Pradesh, India

Dengue fever is an endemic disease in India, transmitted by an infected mosquito bite. In India, the number of concurrent infections and the circulation of multiple dengue virus (DENV) serotypes has increased in recent decades. Molecular surveillance among the DENV serotype is important to keep track of the circulating serotypes, evolutionary changes, and key mutations that can alter the diagnostics. The current study included patients admitted for dengue in the Eastern Uttar Pradesh (E-UP) region during 2018-2019. The genetic characterization of the circulating DENV was accomplished through partial CprM (511 bp) gene amplification via reverse transcriptase polymerase chain reaction and sequencing. Phylogenetic analysis revealed the circulation of all four DENV1-4 serotypes. DENV-2 was the most abundant serotype (44%, 27/61), followed by DENV-3 (32%, 20/61). DENV-1 had a 16% (10/61) predominance, while DENV-4 (6%, 4/61) was found to be the least abundant serotype. DENV-2 genotypes were distributed among lineages I (7.4%), II (85%) and III (7.4%) of genotype IV, DENV-3 to lineage III of genotype III, DENV-1 to genotype III; DENV-2 to lineage B (75%) and C (25%) of genotype I. This primary report on the co-circulation of DENV1-4 serotypes from the E-UP region highlights the requirement of continuous molecular surveillance for monitoring circulating DENV serotypes.

Clinical and Molecular facets of Dengue Virus infection from Bengaluru, South India

Background

Dengue virus (DENV) continues to be an epidemic with high mortality rates. The clinical features, especially in the early phase of infection, are nonspecific and there is no single marker that can be reliably deployed for diagnostics. Further, serotype and genotype diversity is not clearly understood. This study was conceived to understand the performance characteristics of various diagnostic markers; serotype and genotype distribution is thus a vital requirement.

Methods

A subset of blood samples was obtained for all the clinically suspected Dengue cases during the period January to December 2017. The samples were tested for IgM and IgG antibodies and NS1 antigen by both ELISA and rapid tests. Real-time PCR, Conventional PCR and sequencing was performed based on the serology results. Correlation of the data with demographic and clinical details was used to analyze the performance characteristics of various tests.

Results

Clinical signs and symptoms could not predict dengue positivity due to lack of specific symptoms. The performance of IgM rapid test was found to be lower than the ELISA method (53.5% agreement). The NS1 rapid and NS1 ELISA tests were comparable (89.2% agreement). Majority of the infections were caused due to DEN-2 serotype and phylogenetic analysis revealed all the sequenced DEN-2 serotypes belong to Genotype IV. Three sequences were deposited into NCBI GenBank (GenBank accession number MW583116, MW579054 and MW579053).

Conclusion

Our comprehensive data suggests that NS1 ELISA and PCR are best used in the early phase of dengue infection (< 5 days post-onset of fever), whereas IgM antibody detection is reliable only in the late phase. We also highlight the unreliable performance of rapid tests.