Mumbai has reported the highest number of dengue cases among all the districts in Maharashtra this year, according to the state health department.
“Mumbai has reported the most cases of all corporation-governed areas,” said Dr Kanchan Jagtap, head of infectious diseases at the state health department.
The BMC’s preliminary data shows 554 Mumbaiites have been infected with dengue so far this year.
“We are still collecting the data for the entire year,” said Dr Mini Khetarpal, chief epidemiologist, Brihanmumbai Municipal Corporation (BMC).
Dr Jagtap said rural areas in the state have reported fewer cases compared to the urban areas in Maharashtra.
According to the National Vector Borne Disease Control Programme (NVBDCP), Maharashtra is among the 10 states with the highest number of dengue cases — with 4,164 cases and 21 deaths recorded so far this year.
According to experts, irregular and unpredictable rainfall this year triggered the formation of outdoor breeding sites for the dengue-spreading Aedes Aegypti mosquito.
“There is both indoor and outdoor breeding in the city, which makes it challenging to eliminate. Also, eggs of Aedes Aegypti can survive without water and very little rain can re-start the breeding,” said R Naringrekar, chief insecticide officer, BMC, adding that despite the large number of cases, citizens have refused to take preventive steps to secure their homes.
Another peculiar feature of dengue transmission, Naringrekar said is the trans-ovarian mode of passing the dengue virus from the adult mosquito to the egg.
“Unlike other mosquito-borne infections, where the mosquito needs to bite a person infected with the virus to get infected and spread it further, some Aedes mosquitoes are born with the dengue virus and hence, they start the transmission with their first bite,” said Naringrekar adding that eliminating their breeding is the only way to check the spread of the disease.
“We need a plan to prevent rather than treat mosquito-borne infections. The burden of dengue in the last three years in Mumbai has been significantly high. Community participation is vital as mosquito breeding is the only source for the spread of the disease,” said Dr Om Shrivastav, infectious disease consultant.
Meanwhile, doctors said between 2014 and January-November 2015, dengue cases in India increased by an alarming 120%.
Multiple factors caused the surge in dengue infection in India and other parts of the world, said Dr AS Dhariwal, director, NVBDCP.
“This year, we witnessed unusual rain pattern. There was also the El Nino effect at play, which altered the climatic conditions of various zones. Regions that are traditionally dry have received heavy rainfall,” he said.
The fatality rate, which refers to the ratio of deaths to the total number of dengue cases reported, has dropped, revealed statistics. In 2014, dengue killed 137 people, while this year, 181 deaths have been reported so far.
According to the NVBDCP, the mortality rate, which was 33 per 10,000 cases in 2014, has dropped to 20 this year. This drop, doctors said, reflects effective implementation of the treatment guidelines issued by the NVBDCP.