Located on the northern bank of the Irtysh River on China-Kazakhstan border in northwest China's Xinjiang Uygur Autonomous Region, Beiwan area is one of the world's four areas most troubled by mosquitoes. In midsummer, its densely distributed pools and swamps become ideal breeding grounds for mosquito. According to the epidemic prevention department, there are up to 1,800 mosquitoes per cubic meter during peak season, and one can kill more than a hundred with a single swat. However, this has not deterred the border guards from fulfilling their duties. Wearing full-body protective suits, they patrol the area everyday.