The unseasonal showers that Mumbai witnessed on Tuesday could result in a sudden drop in temperature over the next few days and result in spread of viral infections. Doctors in the city fear that there could a rise in the cases of people having fever, cold and cough, and in even dengue and malaria cases may return. “The number of virus particles increase whenever there is a difference in temperature. “We are worried about the rise in dengue and malaria cases. Usually, the mosquito-borne cases drop during the months of December and November, but this year we will have to monitor them closely,” she said.