The World Health Organization says a Singapore man who has tested positive for the SARS virus remains a "suspected case" and is not yet being treated as signaling a return of the virus.
"At this stage, we are treating it as a suspected case -- a perplexing case -- but we're not treating it as probable SARS," said Peter Cordingley, the WHO's regional head of public information based in the Philippines.
The patient's fever had recently eased, he added, saying the WHO was awaiting the results of further tests expected to be released Tuesday afternoon Singapore time.
Further samples were being sent overseas for "double-checking", Cordingley said.
He said authorities had already traced people who had had recent contact with the man concerned and none was sick.
Singapore last reported a case of SARS in early May and on July 5 the WHO declared the virus outbreak contained around the world.
Despite that, scientists say they know little about the disease and have warned that it could make a return.
The outbreak of the disease killed more than 800 people and sickened about 8,000 around the world earlier this year.
The disease had a huge impact on tourism and travel, especially in East Asia with fears over the outbreak leading many tourists and business travelers avoiding visits to the area.
In Singapore -- one of the worst affected areas after Chinese mainland, Taiwan and Hong Kong -- the virus killed 33 people and put more than 300 in hospital.
Monday's announcement of a possible new case kick-started emergency isolation procedures at Singapore General Hospital where the patient, who has not been named, first sought treatment.
Three wards have been closed to the public at what is the city's largest public hospital.
Visitors were required to wear facemasks and screened for fever upon entering the hospital.
According to Singapore's Straits Times newspaper the man in question, a Singaporean citizen, worked in a virology laboratory and has not traveled to Chinese mainland or Hong Kong recently.
He has since been placed in isolation at Tan Tock Seng Hospital, Singapore's dedicated SARS facility.
(China Daily September 9, 2003)