Presence of dengue variant puts health officials on alert

Thiruvananthapuram: The city corporation and the district health wing are keeping a close tab on the pattern of dengue infections in the city especially after studies identified DENV3 as the predominant serotype in samples collected by the MCH unit in Pangappara.
This assumes significance considering that in the previous years during large outbreaks in Thiruvananthapuram, dengue was mostly caused by DENV 1&2 serotypes.
The dominant presence of DENV3 in the most recently reported infections is being closely monitored because sequential infection with more than one serotype results in severe disease manifestations and high rates of concurrent infections which has also been mentioned in the study report “Epidemiological and clinical characterization of dengue virus serotypes during 2017–2019 in southern Kerala”.
Dengue virus belongs to the Flaviviridae and there are four distinct serotypes of the virus that cause dengue (DENV-1, DENV-2, DENV-3 and DENV-4).
According to WHO, recovery from infection is believed to provide lifelong immunity against that serotype. However, cross-immunity to the other serotypes after recovery is only partial, and temporary. The MCH unit in Pangappara has picked up dengue cases since the middle of the March mainly in Akkulam ward in areas like Thuruvikkal, Pulayanarkotta, Kottamukku, Thorottukonam and Mangalathukonam.
“We have been deploying our teams for field-level visits since we started confirming dengue cases. A mobile sample collection is also underway in the wake of recent number of infections. The predominant presence of DENV3 is very significant and we are taking all steps to ensure early intervention and to prevent an outbreak,” said Dr Chintha S, medical officer, Pangappara MCH unit, who is also part of the ongoing study on epidemiological and clinical characterization of dengue virus serotypes, which is being funded by the State board of medical research. The health team is collaborating with the city corporation at the ward level to take proper measures for vector control.
“Unlike Covid, in dengue, infection from one serotype would give only partial immunity to another serotype. This is detrimental. In subsequent infection, the old antibody from primary infection will not neutralize the virus. It will also reduce the immunity of the body and virus will multiply. This happens due to antibody mediated enhancement,” said Dr Anish TS, associate professor, department of community medicine, Government Medical College, Manjeri, who is also part of the ongoing study.
In cases, when people are infected a second time with a different type of virus, they may experience “antibody-dependent enhancement”. When this happens, the immune response of the body actually worsens the clinical symptoms of dengue and aggravates a patient’s risk of developing severe dengue.
The study titled “Epidemiological and clinical characterization of dengue virus serotypes during 2017–2019 in southern Kerala” shows that there was a significant serotype-specific difference for platelet count with infections of DENV3 and its combinations. DENV3 cases showed the lowest platelet count, as per the study. In the past three days, dengue cases have been confirmed in medical college, Ulloor, Pattom, Vizhinjam, Jagathy and Pangappara.