As the city experiences the wettest July in five years, it is also seeing the highest number of malaria cases recorded since the 1970s.
At least 13,818 Mumbaiites have tested positive for malaria since July 1; the number of cases has more than trebled over last July, which saw 4,380 cases.
A 56-year-old man from Worli succumbed to malaria on Wednesday, taking the toll of the mosquito-borne disease to 15 this July.
In the 1970s, the World Health Organisation had declared Maharashtra a malaria-free state.
"I have not seen so many malaria cases in the last 28 years of my practice," said Dr Hemant Thacker, consultant physician with Jaslok and Breach Candy hospitals.
An alarmed Brihanmumbai Municipal Corporation (BMC), whose actions are now being monitored by the state government, has cracked down on housing societies to ensure residents do their most to keep the surroundings mosquito-free.
In the last 15 days, the BMC has initiated legal proceedings against 26 societies after mosquito-breeding sites were found on their premises. The housing societies had not complied with guidelines despite notices. Earlier this month, 569 private premises had been issued notices.
"If the offence is proved in court, the penalty is Rs 10,000," said Dr Arun Bamne, chief insecticide officer, BMC.
Civic teams are surveying private premises to check whether the overhead tanks are leaking, are not closed properly and if compounds and terraces have water accumulated, which encourage the breeding of larvae.
Apart from construction activity, the BMC blames the heavy downpour for the surge in malaria.
"July has been one of the wettest in five years and this has led to increased incidence of monsoon-related ailments," said Manisha Mhaiskar, additional municipal commissioner (health).