At least 24 persons living on the fringes of Salt Lake and six residents of a high-rise complex off Sector V are down with dengue. Both places are under the jurisdiction of the Bidhannagar Municipal Corporation.

Residents of the multi-storeyed residential complex said though their campus was well-maintained, they had fallen victim to mosquitoes breeding in surrounding under-construction buildings. Fresh water had accumulated at the sites over the past several months but nobody sprayed larvicide or cleaned the area.

On Monday, a civic team led by Salt Lake mayor Krishna Chakraborty and the mayoral council member in charge of health, Pranay Roy, visited areas around the apartment complex and spotted mosquito larvae in freshwater accumulated at the under-construction sites. They found discarded cups, heaps of styrofoam trays and even broken sanitaryware, with water accumulated inside, dumped on a vacant plot near the complex.

“These construction sites not only have pits dug up where water has accumulated, but we also found stagnant freshwater on several floors of the buildings. We have sprayed larvicide and will serve a notice to summon the builders. They will be asked why they did not ensure that freshwater didn’t accumulate,” Roy said.

While one team went to the surrounding areas, another team went to the complex’s underground parking lot where they found mosquito larvae in a half-filled bucket.

“We found mosquito larvae and have advised the building’s facility management team on what chemicals to use as larvicide. Our teams will keep visiting this area to ensure that there is no dengue outbreak,” said Chakraborty.

A public health expert said unless the civic body showed urgency in destroying freshwater accumulation points to prevent the carriers of the disease from breeding, little could be done to combat dengue.

The dengue-causing Aedes ageypti mosquito, he said, could lay eggs even in a teaspoon of water. It takes around a week for an adult mosquito to emerge from an egg.

One of the residents of the complex, Tanmoy Roy, said that he had fever on September 30. “Two days later I got myself tested for dengue and the tests were positive. I kept taking a lot of fluids and recovered. But within days of my recovery, two children from our complex tested positive for dengue,” said Roy.

Another resident, Kailash Nath Mishra, said his son Ankur, 14, and daughter Akansha, 12, were down with fever. Mishra, a state government employee, said they had been down with fever for the past few days.

“Today, I have just come back home from a clinic where they underwent the NS1 Elisa test for dengue. Although our complex looks clean, most residents are down with dengue and fever,” Mishra said.

A civic body official said that unlike other years, when the vector-control programme ran for 365 days, this time the corporation swung into action for barely a few days.

In Salt Lake, too, several residents are down with dengue and fever, a source in the civic body said.