The 33-year old Chinese man was taken to the city's Queen Elizabeth Hospital by ambulance, complaining of a cough on Monday night.
He was diagnosed with upper respiratory tract infection, a statement from the hospital said.
Results of a SARS coronavirus test were expected later on Tuesday afternoon, hospital spokeswomen Helen Tang said. The patient is in a stable condition, the statement added.
The patient is the first to be put in isolation and tested for SARS in the city since the killer disease was confirmed to have re-emerged in the neighouring Chinese province of Guangdong earlier this month.
Hong Kong was declared clear of the killer disease in June last
year after an outbreak claimed 299 lives there from nearly 1800 infections. Last year's outbreak killed a total of nearly 800 people worldwide and infected about 8000 people in 32 countries.
Hong Kong has stepped up its vigilance against SARS since the disease re-emerged in Guangdong.
More than 160 people have been placed under watch after returning from Guangdong with a fever since 5 January.
Meanwhile, Hong Kong's last SARS patient has been released from hospital after being admitted with the killer virus almost a year ago, health chiefs said on Tuesday.
Dr Joseph Chung Toi-ching, 57, was released on Sunday, a
Hospital Authority (HA) source said.
Chung was in intensive care for four months after being admitted to the city's Prince of Wales Hospital with pneumonia on 17 March last year, HA spokeswoman Connie Lau said.
"He was then subject to rehabilitation treatment from August," she added, without indicating what complications, if any, had kept him in hospital for so long.
A report in the local South China Morning Post newspaper,
quoting hospital and family sources, said Chung had undergone several operations after the onset of complications, including a bout of peritonitis.
The report said he contracted the disease from his daughter, a medical student at Prince of Wales, the hospital where the city's first outbreak took hold early last year.