By GEOFF CUMMING
Patient zero, in the eyes of Hong Kong investigators at least, was Liu Jianlun.
The doctor from Guangzhou, in southern China's Guangdong province, flew to Hong Kong in February to attend a wedding, booking into the Metropole Hotel. There, he reported trouble breathing, severe muscle pain and high fever.
By the time he was admitted to Kwong Wah Hospital, he had unwittingly infected nine hotel guests from several countries with a mysterious new form of pneumonia. They took the virus home to Singapore, Canada and Vietnam.
Liu was affiliated with Zhongshan No 2 Hospital in Guangzhou where, in early February, a man ravaged by pneumonia infected dozens of doctors and nurses. Because the virus has a 10-day incubation period, he most likely left for Hong Kong unaware of his illness.
Many of Liu's colleagues in Guangzhou were already infected, indicating the seriousness of the disease, but Chinese officials did not pass on any information on the outbreak to Hong Kong - a cover-up which contributed to the global spread of the epidemic.
At Kwong Wah, Liu warned that he was highly infectious and died in isolation on March 4. But by then 70 medical staff and 17 medical students were filling the hospital's emergency wards. Visitors to Hong Kong, Singapore and Malaysia have since dispersed the virus to 20 countries as far removed from Guangzhou as Ireland, Brazil and Spain.
Ninety-eight suspected cases in Singapore are linked to three women who went on a shopping spree in Hong Kong and stayed at the Metropole.
In Canada, the outbreak has killed seven people and sent thousands into quarantine. Authorities say a further 178 suspected cases can be traced back to the so-called Scarborough cluster - from Scarborough Grace Hospital where early cases were reported - and seven people who contracted the disease after travelling to Asia.
The Brazilian case highlights the enormity of the task facing health authorities working overtime to contain the virus. The patient, a British journalist, arrived in Sao Paulo on Monday to cover the Brazilian Grand Prix. The 42-year-old woman had covered the previous event in Malaysia and passed through Singapore and London on her way to Brazil.
At a time of worldwide anxiety about chemical weapons and biological terrorism, the global spread of severe acute respiratory syndrome (Sars) is a deadly reminder of nature's power - and a demonstration that in the global village geographic isolation is no longer a barrier to exotic new diseases.
Sars has now killed nearly 80 people and is suspected of infecting more than 2300. The outbreak remains tiny in comparison to previous flu epidemics, but is causing worldwide alarm because of its rapid spread and the likelihood that the virus has jumped the species gap.
It kills around 4 per cent of known victims - a rate higher than the 1918 influenza epidemic which killed at least 40 million. In an average year, influenza kills fewer than 1 per cent of patients.
Moves to restrict travel and precautionary calls to wear masks have inevitably led to over-reaction. In the United States, the headmaster of a school in Connecticut barred 40 students and staff from school for two weeks after a trip to Shanghai and Beijing.
In New Zealand, a Chinese delegation was asked to stay away from a sister-cities conference in Masterton. Whangarei man Glenn Newman returned from a trip through China, Vietnam and Hong Kong this week to find himself locked out of his business by staff fearful that he may have contracted the disease.
"The staff are so paranoid about it ... I'm not annoyed with the staff, they've got young kids," Mr Newman said. "They've seen the news reports and they're worried."
The Director of Public Health, Colin Tukuitonga, this week said an unnecessary degree of panic was creeping into the community.
"You are not going to get Sars from sitting at your desk in an office which you share with a colleague who has just come back from the Hong Kong Sevens and has no symptoms."
But Sars' rampant spread through a tower block in the Amoy Gardens housing estate in Hong Kong, where at least 100 residents have been infected, is worrying doctors and scientists working to identify the virus. Until then, officials believed it could only be spread by person-to-person contact with droplets or mucus - through sneezing, coughing or physical contact.
The Amoy Gardens outbreak has raised the prospect that Sars can be transferred indirectly - for instance, via handrail or lift button contact - or, even more worrying, that it has mutated into an airborne plague.They are now checking the building's sewer system and testing mice to see if the virus can be spread through rodent faeces.
The Hong Kong authorities have been accused of reacting too slowly, not issuing any quarantine orders until 10 days after the first deaths there, and at first playing down the scale of the health risk.
But most venom, particularly in Hong Kong, has been reserved for the Chinese Government, which knew that a fatal new form of pneumonia had struck in Guangdong last November but did not allow it to be made public until February.
Yet officials at the World Health Organisation are optimistic that steps taken in past weeks - including travel restrictions, quarantines, masks and "barrier nursing" by health workers - will contain the epidemic.
"I don't believe [Sars] will become a pandemic," says David Heymann, head of communicable diseases for the WHO. "Overall, I think it's a positive picture."
The co-ordinated international effort to contain the spread of the disease is backed by a global scientific push to identify the virus. In a matter of weeks, scientists have narrowed the search down to two chief suspects: a new paramyxovirus - the disease which causes measles, mumps and rubella - or a new form of coronavirus, a group of viruses which includes the common cold.
In Hanoi, where Sars was identified by WHO disease specialist Dr Carlo Urbani, who later died, there have been no reports of secondary transfers for eight days.
Clinical virologist Dr Lance Jennings, a member of New Zealand's pandemic planning committee, says the WHO is taking heart from the disease's containment in Hanoi and Singapore. But the disease is far from under control in China and Hong Kong, and its spread in Toronto, where seven have died and suspected cases are nearing 150, is perplexing.
Jennings says coronaviruses - so-called because of their halo or crown-like appearance under a microscope - can change characteristics but "the jury is still out on what the primary cause is".
"The scary thing is it's a novel agent and we don't really know what it is yet. Once we know what it is and where it's come from we'll have a better idea of where it's going. We must keep open minds about the causative agent."
The hope held out by doctors is that the virus' detailed makeup will be pinpointed shortly. Some victims have been successfully treated using antibodies in serum from recovered patients, which suggests they developed some level of immunity.
But Jennings says even after the virus' "sequence" is established, work on a vaccine will take months.
The high death rate increases the likelihood that the virus mutated from animals. The Southeast Asian region is a hotbed for animal-to-human virus transfer because of the mass concentration of people, chickens, pigs and aquatic birds.
Influenza begins as an infection of birds, one that does not make its avian hosts ill. A slight mutation allows it to move into people, sometimes via pigs as an intermediate host.
When Sars cases were first identified in Guangdong, experts assumed it was another outbreak of the "bird flu" which killed six people and infected 18 in Hong Kong in 1997.
Professor Peter Curson, an historical epidemiologist at Sydney's Macquarie University, says the world should brace itself for an increase in exotic diseases. Curson says human biological and environmental adaptations have led to more aggressive infective agents and ushered in a new range of diseases.
"We failed to appreciate fully that disease agents change and modify and mutate ... we've thought the magic bullet would cure all, like antibiotics [which created resistant strains].
Human tampering with the environment had made it easier for viruses to mutate. "There is a bit of an arrogance, in a sense we are just one of a competing series of species and bacteria, and viruses are probably more significant in the whole scheme of things than we are," he says.
"I believe that the next 10 to 15 years will see a substantial increase in infectious disease."
Other scientists agree with Curson but find comfort in the co-ordinated international response to the epidemic.
"In the four weeks that WHO has been tracking Sars, much has been learned," the WHO's latest update says. "This is largely because scientists, clinicians, laboratory chiefs and public health officials everywhere have collaborated closely."
Dr Richard Duma, of the US National Foundation for Infectious Disease, this week added to the pleas for calm: "I think it is frightening a lot of people but I don't think it will produce the mortality that influenza will produce."
In an average year, the flu kills anywhere between 250,000 and 500,000 people.
Herald Feature: Mystery disease SARS
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Cough that shook the world
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