The prevalence of mosquitoes in the city last month was higher than the same time last year due to higher temperatures. The mosquito population is expected to reach its peak in June, the local health authority reported on Friday, while warning of the risk of mosquito-borne diseases such as dengue fever.

Officials said there had been reports on imported cases of dengue fever in nearby cities and controlling mosquitoes was an important issue in infection prevention and control.

Pan Hao of the Shanghai Center for Disease Control and Prevention said mosquitoes could spread more than 80 types of infectious diseases and there were 129 countries and regions globally that reported the risk of dengue fever, with 100 suffering a regional prevalence.

"Dengue fever was usually reported in the southern part of the nation, but its prevalence has started to increase due to climate change. With rising personal traffic home and abroad after the pandemic eased, the spread of mosquito-borne diseases like dengue fever has also increased in the city, requiring public awareness," Pan said.

The health authority said the months between April and October are key for mosquito control. A citywide campaign on cleaning and mosquito control would be launched this month, targeting the first generation of mosquitoes by cleaning all residual water indoors and outdoors as well as trash and garbage bins.