"A large number of rescue and relief workers and survivors are now living there, increasing the risk of intestinal and respiratory infectious diseases," a health ministry official said.
Almost 800 medical workers have been dispatched to the region but efforts to disinfect the area were difficult, with human and animal corpses buried under the mountains of debris decomposing, the official added.
Local health authorities said tonnes of garlic and Sichuan pepper, which in China are believed to guard against various ailments, have been sent to Zhouqu.
|More than 2,100 people were dead or missing in flood-related disasters this year in China [AFP]
More than 1,100 people were killed in Zhouqu and at least 600 people were missing after the weekend avalanche of mud and rocks, which levelled an area five kilometres long and 300 metres wide.
The mudslides in Zhouqu are the latest in a string of weather-related disasters across China.
Almost 10,000 police, troops and firefighters were sent to the town to aid the rescue efforts, but relentless downpour made work nearly impossible.
"Rescue work is continuing, but the recent rains have caused some difficulties," Yan Jinxin, a spokeswoman for the Zhouqu county government, told the AFP news agency.
Troops continued to dig through the mud in Zhouqo looking for those missing. But so far they have discovered few survivors.
Al Jazeera's Melissa Chan, reporting from Beijing after visiting Zhouqo, said that continued rainfall is making rescue work difficult because "the water is making the mud sludgier so it's actually difficult for rescue workers to navigate in and around the town [Zhouqo]."
She also said that "it is more difficult for soldiers to dig out those that are trapped underneath in the mud metres below".
"This town is situated at the base of a mountain so it is a very dangerous place to be, so rescue workers have to keep that in mind with the continued raining."
Troops were using excavators and explosives to clear blockages in the Bailong river which cuts through Zhouqu. While there had been fears that a barrier lake created by the rubble could bring further chaos if it were to burst, Zhang Guoxin, vice-director of the Gansu land resources department, said it had been drained.
Zhang also said the risk of any of the dams along the Bailong bursting had been "basically eliminated", according to a statement on the provincial government's website.
The National Weather Centre forecast heavy rains in the coming days and said the threat of additional landslides along the Bailong River was "relatively large".
Before the Gansu mudslides, the government said more than 2,100 people were dead or missing nationwide in flood-related disasters this year. More than 12 million people have been evacuated from their homes in the worst flooding in a decade.