The map of SARS [newsphoto.com.cn]

Researchers in Germany said on Tuesday they had found a weakness in the SARS virus and said a drug being tested against the common cold could be modified to battle the deadly illness.

Severe Acute Respiratory Syndrome has killed 580 people and infected more than 7,000 worldwide. Carried around the world by air travelers, it is caused by a never-before-seen strain of coronavirus.

But this new virus has a weak point called a protease, the researchers report in this week's issue of the journal Science. A protease is key to the replication of the virus. If the virus cannot replicate, it cannot cause illness.

"If you hit this target successfully you have hit the Achilles' heel of the virus," said Rolf Hilgenfeld of the University of Luebeck in Germany, who led the study.

The researchers have been working with relatives of the SARS virus -- one that causes the common cold in people and another that causes diarrhea in pigs.

The protease used by these two SARS cousins is very similar to that used by SARS, Hilgenfeld said.

Hilgenfeld's lab has a drug that blocks the protease, but it is too toxic to use in people. But they found a similar drug being tested against a rhinovirus -- another cause of the common cold.

"Therefore we conclude that a drug that was originated to target a rhinovirus might be a good starting point for the development of drugs against coronaviruses, including the SARS virus."

(Agencies)