Kolkata: Outbreak of dengue likely, but strains milder this time

KOLKATA: With four Calcutta Medical College students being detected with dengue last week, the scare of an outbreak is looming again. However, unlike last year when hospitals were chock-a-block with dengue patients by end-July, the number of persons affected has been low this year.
The degree of intensity, too, has been less, possibly due to the milder serotypes that have been prevalent this year, believe experts.But the worst may not be over yet, they warn. If sporadic showers continue leading to water accumulation and proliferation of larvae breeding grounds, there could be a sudden spurt in number.
Around seven were admitted with dengue at Beliaghata ID Hospital this week. Around 15 are now being treated across six private hospitals in the city. Even though cases have been relatively mild so far, the numbers could rise if intermittent drizzles intensify, said experts.
“While serotypes II and IV were more frequent last year, making the cases more complicated and fatal, serotypes I and III have been prevalent this time,” said Shyamasish Banerjee, consultant at Apollo Gleneagles Hospital. “The serotypes were responsible for the virulent dengue strains that struck last year. Symptoms had been difficult to detect and conditions changed rapidly, often giving doctors no chance to take life-saving measures. But it’s often observed that the serotypes change every alternate year. But if the showers continue, the number of patients could rise,” said Banerjee.
With more than two months of the rainy season remaining, number of patients could rise, said consultant Arindam Biswas. “Fortunately, few have been affected so far and the strains are mild this year. It seems we have more serotype I and III cases that have kept the cases manageable. But with a spurt in the number of patients, serotype II and IV, too, could rise,” said Biswas.
An analysis of blood samples collected from the city and the rest of the state last year revealed that the prevalence of serotype II has jumped from 26% in 2016 to 73% in 2017. Serotype IV — believed to be the most potent of the dengue variants — had jumped from 11.4% in 2016 to 18% last year. Around 50 dengue deaths occurred in Kolkata last year and the altered strain, experts believe, was the principal reason behind the sharp spurt in the number of deaths.
The dengue virus has a new genetic structure now that has made the disease more potent, according to CMRI Hospital head of microbiology Debkishore Gupta. “As a result, serotypes II and IV are now triggering new symptoms that can’t always be identified. Often, the disease is setting in with milder symptoms and turning fatal in a couple of days,” he said. “People are now much more aware, thanks to the sustained campaign. It has made a difference that’s evident in number of patients we have this year,” said Belle Vue Clinic consultant Samarjit Naskar.