Identification of Serotypes of Dengue Virus Circulating in Delhi and National Capital Region in Post-monsoon Period of 2018

Introduction: Dengue is a major global public health issue with around 390 million infections occurring per year. It is the leading arboviral infection in India and is endemic in all states and union territories. In recent years, all the four serotypes have been seen in circulation in Delhi, India but the predominant serotype keeps changing. Considering the differences in the clinical picture caused by the different serotypes, knowledge of the circulating serotypes can help improve preparedness to deal with future outbreaks effectively Aim: To identify the dominant serotype(s) of Dengue Virus (DENV) circulating in Delhi, India during the post-monsoon season in the year 2018. Materials and Methods: Acute phase serum samples of clinically suspected dengue patients presenting to the hospital were tested for the presence of Nonstructural protein 1 (NS1) Antigen (Ag) of DENV by ELISA from August to December 2018. Sixty two non-repetitive serum samples testing positive for the NS1 Ag by ELISA were subjected to Reverse Transcription Polymerase Chain Reaction (RT-PCR) for identifying the serotype of DENV. Results: Total NS1 Ag ELISA positive cases were 462. Of the 62 samples subjected to RT-PCR, dengue viral Ribonucleic Acid (RNA) was detected in 43 samples. The predominant serotype was DENV-3 (32/43; 74.4%) followed by DENV-4 (7/43; 16.3%), DENV-1 (4/43; 9.3%) and DENV-2 (3/43; 7%). Two samples showed dual infection with serotypes 1 and 3 whereas one sample showed dual infection with serotypes 3 and 4. Twenty one out of 43 (48.8%) patients were admitted to the hospital while the rest were managed on an outpatient basis. Most of the DENV-3 infections were mild, except six patients with warning signs and three with severe dengue. On the other hand, although only three cases with DENV-2 were identified, one presented with dengue with warning signs, another with no such sign and the third one had severe dengue. Of the seven patients with DENV-4, four were admitted with dengue with warning signs. Conclusion: The present study found that during 2018, DENV-3 was the predominant circulating serotype in New Delhi, India and most of the DENV-3 infections were mild. Intensive surveillance of circulating serotypes during the early stages of outbreaks can help in predicting the probability of serious outcomes and in calibrating the health care delivery protocols for dengue patients.