An analysis of blood samples by the National Institute of Cholera and Enteric Diseases (NICED) in Kolkata, has found serotype-II virus to be predominant in the city for the third year in a row. The serotype-II virus is the second most dangerous dengue virus.
The result has left experts worried as it shows the city’s immunity to this strain to be significantly low, The Times of India reported. Repeated prevalence of a strain, it has been pointed out, is rare since a population grows immunity to it.
Reportedly, four people have died to dengue in Kolkata this year and around 18 have died in North 24 Parganas. Thousands have been affected across south Bengal districts, say doctors. NICED analyses 1,000-1,500 blood samples sent by the state health department every year. Serotype-II was followed by serotype-III (14%) and serotype-I (7%). An overwhelming 85% of the city’s dengue patients were detected with the serotype-II virus last year.
“Type-II has been more prevalent in Kolkata but type-III has been more common in north Bengal this year,” NICED director Shanta Dutta said. “A particular serotype is rarely responsible for more fatalities unless two strains strike the same patient simultaneously; symptoms then can be severe. There is yet no research-based evidence to show that a particular serotype is more virulent than the rest.”
AMRI Hospital consultant Debashish Saha, however, had a different take. “Type-IV is the most virulent and type-II comes next and it has certainly been responsible for a large number of dengue deaths in Kolkata over the last two years. It is important to note that a drop-in type-II prevalence from 85% to 75% this year has been reflected in the fact that the city has so far recorded fewer deaths than in previous years and the incidence of dengue, too, has come down. The symptoms have been far more harmless than what they would have been two years ago when the city had an outbreak,” Saha said.
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