It only takes a sneeze?

A simple sneeze may have set off a worldwide epidemic. In a cluedo-like scenario, medical "detectives" have traced the first spread of the dreaded SARS disease to a single elevator in Hong Kong.

Health investigators probing the spread of the mysterious global respiratory illness called SARS appear to now know the exact spot that brought at least seven people to a deadly confluence in a Hong Kong hotel on February 21.

They were all waiting for an elevator on the ninth floor of the Metropole Hotel in the Kowloon peninsula.

The elevator of death

Those at the elevator that afternoon, news reports say, included:

The person whose sickness appears to have spread severe acute respiratory syndrome to 11 countries, killing 15 and infecting more than 650.

He was a 64-year-old medical professor from the Chinese mainland province of Guangdong. The province, adjacent to Hong Kong, is the site of a respiratory illness that has infected more than 300 people and killed five since last November.

The catalyst himself

The professor, a physician, had checked in to the Metropole on February 22 to attend a relative's wedding reception even though he had been feeling ill for a week before he left the mainland, the Toronto Globe and Mail reports.

The next day, feeling worse, the professor checked out of the hotel and went into a Hong Kong hospital. He died there March 4.

"We think he must have been coughing and sneezing while he was waiting for that lift," John Tam, chief information officer of the Hong Kong Economic and Trade Office told the Globe "and that's when he infected the other guests."

The American businessman

Hong Kong's top health official also said that the infectious agent apparently travelled through respiratory droplets in the elevator waiting area, and it proved to be "very, very infectious."

A 48-year-old American businessman based in Shanghai was also in the elevator.

From Hong Kong, the businessman flew to Vietnam and was hospitalised in Hanoi almost as soon as he stepped off the plane. He then requested to be returned to Hong Kong, where he was hospitalised again. He died there March 13. In Hanoi, a French doctor and nurse who treated him at the Hanoi French Hospital died this week.

"His name was Johnny Chen," s Hoang Thuy Long, director of Vietnam's National Institute of Hygiene and Epidemics told the Associated Press. "When Mr. Johnny Chen came to Vietnam, he was actually in an incubation period."

Vietnam now has 62 suspected cases of SARS.

The Toronto couple

A 78-year-old Toronto woman and her husband were the next unfortunate characters in the elevator.

She and her husband were checking out of the Metropole that afternoon. The couple then spent the night with their son in Hong Kong, before returning to Canada February 23. The woman died of SARS on March 5. Her son died March 13. Her husband, daughter and another son are in intensive care in Toronto, and her five-month-old grandchild is being monitored at Toronto's Hospital for Sick Children.

How SARS spread to Canada and Singapore

Another Canadian, a 55-year-old British Columbia man, also stayed at the hotel with his wife between February 20 and February 24. He is in critical condition in Vancouver.

Canada now has 9 suspected cases. Other hotel guests on the same floor while the professor was there include three women from Singapore, who all became ill after they returned home.

Singapore now has 39 suspected cases.

At least 34 of those infected in Singapore had been in contact with the three women, according to Singapore's Health Ministry, which on Saturday was preparing to empty out one hospital to deal only with SARS cases.

The Hong Kong "index patient"

Also at the hotel while the professor was there was a Hong Kong man who visited a friend on the ninth floor. He became the Hong Kong "index patient" who spread the disease to the Prince of Wales Hospital.

Hong Kong now has 203 suspected cases.

Hong Kong also has four deaths, in addition to the American businessman and the Chinese professor. The latest fatality is a relative of the professor.

Confirmation that the professor had been at the Metropole sent health officials on the road to Beijing to examine more closely the outbreak in Guangdong.

The World Health Organization said Friday a team of five people was headed to China for five days beginning Sunday. And the US Centres for Disease Control and Prevention also said Friday it too would help.