Health authorities around the world are struggling to contain a lethal form of pneumonia as air travellers spread it across the globe.
Officials are urging people not to panic
The World Health Organisation (WHO) issued a rare emergency warning over the weekend, declaring the sickness "a worldwide health threat", and saying that cases had been reported on three continents, with more suspected in other parts of the world.
So far, there have been four deaths related to the pneumonia and another five in an outbreak of a similar infection in a province of China, although the two have not yet been definitively linked.
Around 200 people are also believed to have been infected world-wide in the last week alone.
New suspected cases
In the latest cases reported, authorities in Geneva said that two people were in isolation in a hospital after exhibiting symptoms similar to those of the disease, Reuters news agency said.
A British man returning from Hong Kong has been admitted to hospital with a suspected case - the UK's first.
And in Australia two women who had recently travelled to China have been hospitalised with symptoms, French news agency AFP reported, although doctors stressed there was no proof they were suffering from the illness.
The Prime Minister of New Zealand, Helen Clark, told a news conference that WHO experts believed it might rival "Spanish flu" in 1918 - which killed at least 20 million and possibly double that number.
However, an expert from the WHO played down fears.
Pascale Brudon said: "Today we don't know enough about the outbreak to be able to say that. I would be less alarmed than that."
A British expert says that it is unlikely that the illness is flu - the most frightening scenario for experts.
Professor John Oxford, a world-leading figure in virology, based at Queen Mary's College in London said that the fact that a culprit had not yet been identified was good news.
He said: "If it was influenza, I expect we would have heard this by now. That's certainly rather reassuring.
"This has been smouldering around the Far East for some time - it's not as if it has just exploded, I wouldn't get too worried."
The WHO has warned travellers and airport staff to be on the look-out for signs of the condition, known as Severe Acute Respiratory Syndrome.
Its symptoms include high fever and breathing difficulties, and it has an incubation period of two to seven days.
The outbreak is thought to have begun in the Vietnamese capital of Hanoi last month, after an American businessman travelling from Shanghai infected hospital workers before himself dying of the disease.
The illness is thought to be highly contagious
A Vietnamese nurse who died on Sunday is thought to have given him treatment during his time in Hanoi.
As many as 40 others in Hanoi are thought to be infected.
On Sunday, the WHO said two deaths had been reported in Canada.
The two are thought to be a mother and child returning from Hong Kong, where up to 100 people have already been taken ill.
In Germany a doctor suspected of having caught the virus whilst in Singapore is currently in quarantine.
There are also reports of suspected cases of the disease in Switzerland, France, Slovenia, Taiwan, Thailand, China and the Philippines.
However the East Asian region is the worst affected by the disease.
In addition to cases reported in Hong Kong and Vietnam, authorities in Taiwan and Singapore have reported cases of the disease.
No figures are available yet from China, but the WHO said the flu-like symptoms of the disease were similar to those of a sickness in the southern province of Guangdong last month which infected 305 people, killing five of them.
"All we can tell you right now is that the disease situation here has been placed well under control," a Chinese government spokeswoman said on Monday.
Japan has sent a team to Vietnam to help investigate the cause of the outbreak.