But Zeng was not worried about that, saying time-old remedies such as using rodenticide proved effective.

He said a German-made rodenticide was popular with Chinese CDC workers. The rat extermination drug was added into a bitterness agent and a means that could prompt vomiting.

"If a man mistakenly takes it, the drug can be spit out upon the effect of the agent. It's safe to people and the environment," Zeng said, adding rats die immediately after taking it even in 2008 -- the Year of the Rat.

The CDC has conducted various tests on rodenticides and pesticides. Zeng said the ultimate product should be environment-friendly, efficient and non-poisonous.

It also set up a "citywide surveillance network," consisting of 360 monitoring stations. It has evaluated the outcome in preventing and controlling outbreaks of pests.

A pest-control expert since 1985, Zeng said people's awareness in preventing pest-related diseases was greatly improved compared with 20 years ago.

The city's CDC has spent 10 million yuan (US$ 1.4 million) on relevant facilities, such as GPS monitoring instruments, Zeng said, adding laboratories and spray facilities were most advanced which enabled researchers to observe pest's drug-resistance via a gene chip during molecule studies.

He said he hoped the Olympic Games could boost the city's disease prevention level. "In Mao's era, we merely mobilized the masses to kill harms. But now we use a more scientific way; pest control has developed into a specialty."

Zeng's team was mainly in charge of Olympic constructions. As for the vast urban area, a massive "patriotic sanitation movement" was underway.

The Beijing Patriotic Sanitation Movement Committee on Thursday sent 3 million cell phone messages to residents, calling on every family to move to clean trashes and kill baneful insects. The committee handed out 450,000 promotion papers and 40 tonnes of pesticides.

"A unified action is necessary as cockroaches cannot be exterminated effectively if a neighbor was not willing to cooperate," a sanitation official, surnamed Zhang, said in the eastern Chaoyang District, an area which contained 25 of the city's 31 Olympic venues.

Zhang said cockroaches could easily run to other corners of a building so the entire building should move to kill.

"Since SARS broke out in 2003, people have begun to pay attention to public health. Some southern cities began to clean up streets and kill masked civets and harmful pests."

In the 1950s, Chairman Mao launched the Four Harms Eradication campaign to get rid of pests, which originally were rats, flies, mosquitoes and sparrows. In the absence of sparrows, locusts consumed many crops, which later became disastrous.

Mao instructed in 1960 that sparrows should not be included in the kill list, which, instead, changed one of the four harms to bedbugs.

Another war against the "New Four Harms" was also in its peak in the city now, targeting spitting, swearing, queue-jumping and smoking in public places.