Co-circulation of all 4 serotypes of dengue virus in endemic region of Saurashtra, Gujarat during 2019  

Dengue is a fast emerging mosquito-borne viral disease endemic in many regions, causing a severe flu-like illness and sometimes potentially lethal complications. Its causative agent-the dengue-virus, belonging to the genus Flavivirus, has four serotypes, namely, DENV-1, DENV-2, DENV-3 and DENV4. These may either mono-infect or co-infect a patient based on their prevalence and predominance in the given region and time; hence conferring the potential to cause global pandemics. Aim: To study  epidemiology of dengue, determine the circulating serotypes and patterns of co-infection in Saurashtra region of Gujarat, India. Total 11,181 blood samples of clinically suspected dengue cases were studied over a period of one year, from Jan 2019 to Dec 2019. The serum was tested for Dengue NS1 Antigen using Microlisa test kit (symptoms < 7 days) and for Dengue IgM Antibody using NIV Pune test kit (symptoms >7 days). After serological confirmation, 120 samples from different geographical areas were selected for serotyping by Dengue specific RT-PCR. Out of the 11,181 samples tested, 3998 (36%) had serologically confirmed dengue. The proportion of male cases (60%) was greater than that of females and majority of confirmed cases belonged to the age group of 21-35years (41%) followed by 6-20years(34%). Seasonal trend showed a gradual increase in positivity starting from June with a peak in October (39%). Circulation of all four serotypes was observed with predominance of DENV-1(44.8%),  followed by DENV-4 (22.6%), DENV-2(21.5%) & DENV-3 (6.45%). Co-infection of DENV-1 & DENV-2 (2%), DENV-1 & DENV-3 and DENV-1 & DENV-4 (1%) was observed. The study concluded that all 4 Serotypes co-circulated in the Saurashtra region of Gujarat during 2019; since the immunity to one serotype does not protect against a heterotopic serotype. Dengue cases constituted mainly of adult male population ( 21-35yr) and showed a seasonal peak during monsoon and post-monsoon periods, which coincide with increased vector breeding; hence emphasizing on effective implementation of vector control & personal protective measures for disease control.