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A recent study by doctors from the Bruhat Bengaluru Mahanagara Palike (BBMP) and NIMHANS has found a striking predominance of dengue virus type 3 (DENV-3) in Bengaluru between April and July this year, when the disease was at its peak. The study was published in The Lancet last week. The number of dengue cases this year touched 27,490 as of Tuesday, the highest ever in Karnataka.
As many as 12 dengue deaths were recorded this year of which three are from BBMP limits. Early this month Karnataka notified dengue as an epidemic . However, the number of cases have been declining in the last fortnight.
Dengue virus (DENV) has four serotypes, and is transmitted to humans by the day-biting Aedes aegypti mosquitoes. While some studies indicate that particular DENV strains are more virulent than others, doctors said a secondary infection in dengue patients determines the severity of the disease. Samples from eight zones To assess the current serotype distribution in Bengaluru, doctors analysed 1,600 samples from acute febrile illness patients across all eight zones of urban Bengaluru (East, South, West, Bommanahalli, Dasarahalli, Mahadevapura, Rajarajeshwarinagar, and Yelahanka).
Samples were collected through health centres under BBMP during the outbreak between April and July 2024 and tested at the civic body’s sentinel laboratory in H. Siddaiah Referral Hospital. Of these, 549 (34.
3%) tested positive for dengue NS1 antigen and/or anti-dengue IgM by ELISA., said Shruthi Uppoor, consultant microbiologist at the sentinel lab in H. Siddaiah Referral Hospital, who is one of the lead authors of the study.
“Of the 549 dengue positive samples, 507 (92.3%) were NSI antigen positive. We sent only the NS1 samples to the Department of Neurovirology at NIMHANS for serotyping (as only the NS1 samples are eligible) to assess the circulating dengue virus in the city,” she said.
DENV-3 predominant Of the 507 NS1 positive samples, 228 (45%) tested positive for DENV serotypes through polymerase chain reaction (PCR) tests. “Real-time PCR analysis of the 228 samples revealed a striking predominance of DENV-3 (79.8%), followed by DENV-1 (11.
8%), DENV-2 (8.3%), and DENV-4 (1.3%).
Additionally, 1.3% (3) of the samples showed DENV-2 and DENV-3 co-infection,” Reeta S. Mani, professor and head of the Department of Neurovirology at NIMHANS, told The Hindu .
Pointing out that DENV-4 was predominant in Bengaluru previously, Dr. Mani, who is the corresponding author of the study, said: “Our findings indicate a potential shift in serotype dominance towards DENV-3 from DENV-4, which has been the predominant serotype in southern India since 2015, based on evolutionary studies of DENV. The complex immunological dynamics of dengue virus serotypes pose considerable obstacles to the development and implementation of effective dengue vaccines in India.
As the country prepares for phase 3 trials of quadrivalent dengue vaccines , understanding region-specific circulating dengue virus serotypes is crucial.” “The dominance of DENV-3 is particularly significant given the challenges some vaccine candidates face in providing protection against this serotype. The high prevalence of DENV-3 in this study presents an unique opportunity to generate robust efficacy data for this serotype in upcoming phase 3 trials in India, addressing a key gap identified in previous international trials.
To further enhance our understanding of dengue epidemiology and support vaccine development efforts, dengue virus sequencing is crucial,” Dr. Mani added. Published - September 18, 2024 07:00 am IST Copy link Email Facebook Twitter Telegram LinkedIn WhatsApp Reddit viral diseases / bengaluru / Karnataka / medical research / disease prevention / vaccines.
