Health officials called on residents Thursday to take the time to clean up any standing water in their area due to the recent increase in the city's mosquito density.

This year's mosquito density is up 37.8 percent from last year, according to the Shanghai Municipal Health Promotion Committee.

"The warm weather and the rain have provided mosquitoes with favorable breeding conditions," said Zhou Yibin, an official with the Shanghai Municipal Center for Disease Control and Prevention.

Health officials keep an eye on the insect's population because mosquitoes and other pests can spread certain diseases in the city.

Pest-borne diseases typically occur at a low rate. "There are no more than 10 cases of dengue fever each year," Zhou said at a press conference Thursday. "The majority of the cases involve travelers who contracted the disease while visiting Southeast Asia or Africa."

Japanese encephalitis is one of the most common pest-borne diseases. It primarily occurs in the city's migrant population, which does not have a systematic vaccination record, said Li Zhongyang, vice director of the Shanghai Municipal Health Promotion Committee.

Health authorities have undertaken new measures to track pest control equipment, such as rat traps and fly catchers, in residential compounds.

"We are starting to put up maps that show the exact locations of the equipment in neighborhoods," said Xu Yuan, vice director of the committee's general office. "It can help our volunteers maintain the equipment on a regular basis. There is also a safety concern for children and animals."

Xu suggested that residents use the maps to prevent young children and pets from going to where the equipment has been set up.

The committee is considering asking neighborhoods with a lot of expats to create English versions of the maps and warning signs for the pest-control equipment.

Authorities suggested that households with pest problems call the 12320 health hotline.