Preliminary lab results indicate that a government doctor who became ill in Taiwan while investigating SARS (search) does not have the disease, the Centers for Disease Control and Prevention said.

More tests will be conducted to see if doctors can rule out the coronavirus that causes SARS as the source of Dr. Chesley L. Richards' illness, CDC (search) spokesman Tom Skinner said Tuesday.

Skinner said Richards is in isolation, but would not say whether he was in a hospital or at his suburban Atlanta home.

"He continues to be doing very well," Skinner said.

Richards, a CDC infection control expert, returned to the United States last week after he developed a fever and cough last week that indicated the possibility of SARS.

Three other CDC officials -- a doctor and two other disease experts who had contact with Richards when he became ill -- also returned from Taiwan (search) and were examined but did not show any SARS symptoms, Skinner said.

Richards went to Taiwan May 15 to analyze infection control procedures in hospitals as part of the CDC's SARS investigative team. Taiwan has had dozens of deaths from the disease.

More than 700 people have died from SARS worldwide.