"Monsoon is a favourable season for transmission of the virus. With the rise in temperatures, the number of cases would gradually reduce. In winter, we can expect a marginal rise but the number of cases could not be as high as that reported in monsoon," said Dr Abhay Chudhary, director, Haffkine Institute, Parel.
Also, the number of swine flu deaths reduced from three in August to one in September. "The dip in cases is a result of the seasonal variation. Some months, there will be more cases and some months there will be fewer. The mortality has gradually reduced," said Dr Om Shrivastav, infectious disease specialist, Jaslok hospital, Peddar Road.
Dr Shrivastav said that factors such as overcrowding, pollution, environmental changes due to reasons like rise in construction activity make people vulnerable to such infectious diseases.
According to Dr Mangala Gomare, epidemiologist, BrihanMumbai Municipal Corporation, said the number of swine flu cases would dip further with the change in temperatures. "In the last three months, there has been a steady decline in the number of cases," said Dr Gomare.