Shanghai on Monday began a 10-day campaign to kill mosquitoes across the city.
Leng Pei'en, a Shanghai Municipal Center for Disease Control and Prevention (CDC) official, told reporters April was a vital period for mosquito control efforts.
"Experience has shown it will efficiently reduce the number of mosquitoes at the peak of summer by way of controlling the first generation of mosquitoes in early spring. It will in turn curb incidence of diseases spread by mosquitoes so as to create a fair environment for the Olympic Games' soccer matches scheduled to take place in Shanghai," he said.
The snowy weather earlier this year didn't affect the hibernation of mosquitoes in the eastern seaboard city, he added.
The CDC investigation shows that the overall mosquito intensity in the city is about 20 percent higher this year.
The data revealed the mosquito concentration rate in downtown Shanghai had dropped 46.15 percent in March in comparison to the same period last year. In areas beyond the city's outer ring, the rate increased 134.85 percent.