At least five districts in southern West Bengal have witnessed a surge in dengue cases with each having reported more than 100 vector-borne infections till July 20, an official said on Tuesday.

He, however, claimed that the situation was not alarming.

North 24 Parganas with 268 dengue cases topped the list of districts.

Other districts in south Bengal where the number of dengue cases is high are Murshidabad district (224) Hooghly (181) and Calcutta (152).

Malda district in north Bengal has also reported around 230 cases, he said.

"The dengue situation in West Bengal is not alarming. This disease has a seasonal pattern that shows an increasing trend with the onset of monsoon and peaks after the season. This year the number of dengue cases is comparatively low," a senior official of the state health department told PTI.

The graph of dengue infection in Bengal was much lower than last year, he claimed.

"But in the last few weeks, primarily due to the rainwater accumulation in several areas, there has been a surge in dengue cases. We have been active since the beginning of this year to prevent the infection," he said.

Since early this year, the civic bodies have been "proactive in removing garbage and stagnant water", he said, adding that at the block level specific routines have been followed to control the disease.

"As a result, the graph of dengue infections was much lower in the January-June period. The heavy rain in the last few weeks has caused waterlogging in various places. Mosquito larvae have also been found in drains, abandoned houses or garbage, especially in urban areas," the official said.

He referred to a survey conducted in Howrah district, which found the number of dengue cases in the municipal area was seven last week.

"Two people were found to have been infected with this mosquito-borne disease in the Bally Municipality area and the remaining five people were from different rural areas of the district," he added.

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