Door-to-door inspection in various pockets of the city has failed to establish a direct link between the breeding of the Aedes aegypti mosquito and the outbreak of dengue, civic health officials said on Sunday.
A health official of the Calcutta Municipal Corporation (CMC) said that during the inspection, it was found that areas where people were infected with dengue, no Aedes aegypti larva was found, and vice versa.
'The finding has raised doubts about the Breteaux Index, which is used for measuring the possibility of a dengue outbreak in an area,' said chief municipal health officer Deb Dwaipayan Chattopadhyay.
According to civic entomologist Debashis Biswas, the Breteaux Index is a yardstick for mapping the dengue outbreak in a particular area.
The number of containers in which Aedes aegypti larvae is found is divided by number of houses visited and the quotient is multiplied by 100. If the index is less than five, it means there is a remote possibility of dengue outbreak.
The civic officials said in the areas like Bagbazar, Bowbazar and Beleghata, where the Breteaux Index was 10, 12 and seven, respectively, not a single person was found infected with dengue.
On the other hand, in the Tollygunge and Prince Anwar Shah Road areas, where people were found infected by dengue, the Breteaux Index stood at one.
Chattopadhyay said as there is no specific drug or vaccine for dengue, the only way to prevent the disease is by destroying the mosquito's breeding grounds.
The civic authorities are planning to launch an audio-visual awareness drive.
'We will teach people how to prevent dengue and try to rope in cinema and sports personalities for the campaign,' said a civic official. The civic authorities have also decided to spray pesticide with the help of fogging machines.
The officer added that no fresh dengue case had been reported in past three days.
So far, one person has died and 19 persons have been found suffering from dengue. The dengue death toll in the city last year was 12.