PUNE: A “nasty strain” of the mosquito-borne viral disease has been blamed for this year’s severe dengue outbreak, according to scientists.
The Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) revealed that dengue virus 2 (DENV-2) is the main circulating strain or serotype in Maharashtra this year after a molecular investigation of the blood samples of 1,413 dengue infected patients.
Dengue virus has four distinct strains — DENV-1, DENV-2, DENV-3, and DENV-4. Treating doctors said they were also coming across patients showing early onset of severe symptoms and rapid progression — some of the fairly identifiable traits of DENV-2.Another important indication coming forth this year is DENV-2’s ability to “superinfect” the previously infected individuals, causing an enhanced or double-antibody response leading to an increased virus intrusion in cells and triggering a severe inflammatory response, higher organ penetration. All these factors are eventually leading to clinically severe illness. Some of the prominent cities, such as Pune, had three strains — DENV-1, DENV-2, and DENV-3 — cocirculating in 2019-20.However, there were comparatively fewer cases. As a part of the National Vector Borne Disease Control Programme (NVBDCP), ICMR-NIV supports the state of Maharashtra and Goa to understand the circulating serotypes of the dengue virus. Recently, Andhra Pradesh and Telangana have been added to the list. The ICMR-NIV Bengaluru field unit supports the state of Karnataka.
“For the year 2021, ICMR-NIV has tested 1,413 samples from Maharashtra, 209 from Goa, 28 from Andhra Pradesh and 385 samples from Karnataka. DENV-2 is a predominantly circulating serotype in the states of Maharashtra, Goa, Andhra Pradesh and Karnataka. Earlier in 2018, DENV-1 and DENV-3 were the predominantly circulating serotypes in Maharashtra,” an ICMR-NIV official said.In addition to adults, the dengue virus strain is affecting a lot of children too. “This year, we are witnessing more and more children with severe dengue. Hence, it appears to be a more severe dengue season in comparison to the previous years’,” said Deenananth Mangeshkar hospital’s paediatric intensivist, Sumant Patil.
“DENV-2 does not have a very specific manifestation separating it from other strains but can be recognized by early onset of severe symptoms and rapid progression,” he said.
The dengue cases peaked in Maharashtra between August and October this year. “The cases have not come down very much as of now but stabilized and not worsened further,” Patil said.
“Some of the northern states such as Delhi, Uttar Pradesh, Bihar and southern states such as Andhra Pradesh, Karnataka and Tamil Nadu have an ongoing dengue health crisis in adults as well as in children, mostly related to DENV-2,” he added.
Secondary dengue is the biggest risk factor for severe dengue and doctors have been witnessing a rise in such cases over the last four months.
We saw quite a surge in cases of secondary dengue infection this year in the past four months, where dengue is very severe and patients undergo a lot of complications,” said Pune-based physician Abhijit Lodha.
During a primary (first) dengue infection, the patients’ IgM dengue antibody levels are very high, but they test negative for IgG dengue antibody. “But in the secondary (second time) dengue infection, patients test positive for both the antibodies. And their IgM antibody levels are lower than IgG. The levels of IgG actually increase during secondary infection,” Lodha said.
The state registered 6,374 cases of dengue and 1,537 cases of chikungunya till September 14. Eleven persons have so far died due to dengue viral fever. There were 2,029 cases of dengue and four deaths from the disease and 422 cases of chikungunya were registered during the same period last year.