翻译原文：

For the past two weeks residents living around China's second largest lake have been able to smell a rat—make that two billion rats.

 When the Yangtze River flooded on June 23, the water level rose in Dongting Lake, which sits along the river south of Wuhan in central China's Hunan Province .

 The flooding began flushing out rat holes around the lake, triggering a literal rat race for higher ground.

 Since then farming communities in more than 20 counties near Dongting have been overrun, observers say.

 "For the past week, the situation has been very serious," Tan Lulu, who works for the international conservation group WWF, told National Geographic News from WWF's Hunan office in Changsha.

 Farmers are using everything from poison to hammers—and even their bare hands—to kill the rodents, Lulu noted.

 "There are so many rats that you can kill three of them with one [strike]," she said, adding that the banks of the lake are carpeted with dead rats.