Regions around the epicenter of the earthquake will experience warmer weather over the next three days, the China Meteorological Administration (CMA) said on Friday.
It forecast temperatures of 25 to 29 C in the quake zone and, given the large number of corpses lying in the open, called for intensified measures to prevent the spread of disease.
"The smell of corpses has become increasingly strong," Yang Lei, a reporter based in Beichuan county, one of the worst-hit areas, said.
"I am wearing two layers of gauze masks, but I can still smell it."
A journalist from China Central Television said rats were increasingly present in the county.
Yang said that although some steps had been taken to clean up Beichuan, "It is still not enough, especially if the temperatures rise in the next days, as the hygiene conditions will get worse".
So far, no epidemics have been reported in the quake-hit regions, Vice-Minister of Health Gao Qiang told reporters in Beijing on Thursday.
Responding to a question from CCTV concerning diseases in the disaster area, Gao said: "We will try to achieve the goal of no big epidemic after a great disaster."
The goal is based on scientific evidence and plans, he said.
China has been able to control epidemics after all its major natural disasters since 1976, including the huge quake in Tangshan, he said.
Besides epidemics, environmental experts are also worried the water supply in quake-hit areas will become contaminated by viruses, which thrive in high temperatures.
The CMA also said on Friday that rain is not expected over the weekend but clouds could affect air rescue and relief work.
Local residents and rescue workers should be wary of possible landslides, and mud and rock flows caused by aftershocks and rain, the CMA said.
On Thursday, a landslide happened in an area between Dujiangyan and Wenchuan county, shortly after soldiers managed to clear a damaged road.
Geological disasters are also likely to affect parts of western Yunnan province, the CMA said.
(China Daily May 17, 2008)