A decade on from the Sars outbreak, experts agree that the disease could return - but its effects are unlikely to be as devastating as in 2003.
Hong Kong is now fully capable of battling an epidemic - such as severe acute respiratory syndrome - thanks to much improved infrastructure and management software, they say. But that's no reason to be complacent in the battle against contagious diseases.
While Sars remains on their watch list, microbiologists are far more concerned about other biological threats - not least the H5N1 strain of bird flu.
Their concern has been sparked by the growing realisation of the risk of viruses crossing between species - much as Sars jumped from the Chinese horseshoe bat to the wild civet cat and then to humans.
The same could happen again - with Sars or another virus.
"We cannot say the Sars virus is gone," said Professor Joseph Sriyal Malik Peiris of the University of Hong Kong's School of Public Health. "We have to respect the ever-changing nature of micro-organisms ... it would be a mistake to believe an infectious disease can be put into a box and under control. It can continue to find a new host and mutate, or grow resistant to antibiotics."
Microbiologist Professor Guan Yi, also of HKU, agrees. "No one can be sure whether the Sars virus has really vanished from this world. Apparently the infectious chain has been cut off. But as long as people in China are secretly eating wild animal, the threat is still there."
Guan gained worldwide fame in May 2003 when he tracked down civet cats - sold for food at a Guangdong market - as a host of the virus and likely source for transmission to humans. But it took him months to get mainland authorities to close the market.
"After slaughtering some 500 animals in the market, new infectious human cases stopped. I believe this was when we cut off an infection chain," he said.
But now, a decade on, the market in wild animals for food is reviving. A survey last year by the Beijing-based Horizon Research Consultancy Group showed that 26.9 per cent of residents in five mainland cities - Beijing, Shanghai, Kunming , Nanning and Guangzhou - ate wildlife in the previous year. In Guangzhou, the ratio was 83.3 per cent.
"Wild animals are often fine on their own. But when hundreds of them are being kept together, viruses on them may jump to other species and occasionally there may be one or two cases [of virus mutation]," Guan said.
"We can expect there will be three to four pandemics this century, and we have [already had] one," Peiris said of Sars, citing past research into pandemics.
It's difficult to predict how, when or where the next pandemic will strike, or the extent of its effect on our increasingly interconnected world. But as a pioneer in the field of pandemic research, Peiris is confident in saying that the next infectious disease to threaten the world will come from animals.
The World Health Organisation says 70 per cent of infectious diseases to emerge worldwide in the past three decades were animal-related.
"The H5N1 avian influenza is the most scary one. If it could be transmitted human to human, the consequences could be catastrophic," said Peiris. "It could be more serious than Sars."
But optimism that Sars will never threaten like it did in 2003, when it claimed the lives of 299 people in Hong Kong and infected 1,755, appears well placed.
Post-Sars, there are now many procedures and practices in place that simply did not exist 10 years ago, when an infected doctor from Guangdong checked into a Kowloon hotel, triggering the start of the outbreak here.
The changes include better infection control infrastructure, cross-border co-operation on health, quarantine procedures, medical technology and more attention to good hygiene.
At a governmental level, cross-border work on health was non-existent a decade ago. Now, a sophisticated and comprehensive network is in place. The Centre for Health Protection was established in 2004 to strengthen disease surveillance and infection control systems. Princess Margaret Hospital in Kwai Chung is home to a new infectious disease centre. The Hospital Authority set up a three-tier alert system to respond to outbreaks of infectious disease. All medical staff in public hospitals have undergone training in infectious diseases and developed the habit of wearing surgical masks.
The public have changed their habits since the pandemic, from wearing masks to using hand sanitisers and even using serving chopsticks to dish up food from common dishes to different diners. Lift buttons and surfaces on public transport are sanitised several times a day.
Guan said the outbreak of swine flu (H1N1) in 2009 was the first live test of the emergency response system set up after Sars. "The city passed a small test. The response was quick and the system is already mature. I give it 99.5 marks out of 100. We are the best in handling this [disease outbreaks] … we should be proud."
"[If Sars returns] it will not cause a big disaster again. It will not have the chance," Guan said.
Peiris agreed, but he stressed that his biggest worry remains H5N1 bird flu, which first jumped the species barrier in Hong Kong in 1997, killing six people. "Swine flu would be a picnic compared to [an outbreak of H5N1]."
He said it was the nature of Sars that made the use of quarantine in 2003 so effective. When a person contracts Sars, their level of contagiousness remains low for the first two days but is most contagious four to five days after the disease is picked up.
"By the time a patient becomes very contagious, they are very likely to be in a hospital and under isolation, as in the later stages of the outbreak in 2003. That means a good quarantine system is effective in preventing transmission in the community."
But such a method may not be so effective for a form of influenza, where a patient would be most contagious in the first two days of the illness. "Before a patient is located and quarantined, the virus is already spreading," he said. "There is no way we can stop the outbreak in the same way as Sars was stopped."
With this in mind, top microbiologists are trying to stay ahead of changes in dangerous infectious diseases. Since Sars, their attention has turned from human diseases to viruses that can be transmitted from animals to humans.
"We know that micro-organisms are changing constantly and disruption in the natural order allows them new ways to cause problems. We need to go on with the research to keep ahead of these problems." Peiris said.
HOW SARS TOOK HOLD
November The first case of atypical pneumonia, later identified as severe acute respiratory syndrome (Sars), is reported in Shang Ling, a village in Foshan, Guangdong
Feb 11 Beijing's Ministry of Health reports 300 cases, involving five deaths, of an "acute respiratory syndrome" in Guangdong
Feb 21 A 64-year-old medical professor from Guangzhou checks into the Metropole Hotel in Mong Kok. He will become the index patient for the Sars outbreak in Hong Kong, from where it will spread around the globe.
Feb 26 First cases of unusual pneumonia in Hanoi, Vietnam
March 10 Eighteen health care workers at Prince of Wales Hospital, Sha Tin, report that they are ill. Within hours, more than 50 hospital workers are identified as having had a febrile illness
March 14 Health secretary Dr Yeoh Eng-kiong says "this is still not an outbreak". The man who will become the index case for the Amoy Gardens outbreak stays overnight at his brother's flat in the private housing estate.
March 15 WHO confirms that Sars is a "worldwide health threat" and that possible cases have been identified in Canada, Indonesia, the Philippines, Singapore, Thailand and Vietnam. It issues guidelines warning travellers to Southeast Asia, including Hong Kong, about the dangers of Sars.
March 22 The University of Hong Kong announces a coronavirus is responsible for Sars. A diagnostic test is developed.
March 27 The chief executive announces emergency measures, among them a closure of schools.
March 30 An isolation order is served on Block E of Amoy Gardens in Kowloon Bay. Residents are ordered to remain in their flats for 10 days. Some 321 cases are detected at the estate
April 1 Government experts find evidence that sewage and drains might have been involved in the vertical spread of Sars in Amoy Gardens' Block E. Residents are evacuated to holiday camps to continue their 10-day quarantine. The eventual toll is 329 infected, with 42 deaths at the estate.
April 2 WHO recommends that non-essential travel to Hong Kong and Guangdong be postponed.
April 15 Hong Kong's disease prevention law is amended to allow stronger measures to prevent the spread of Sars.
April 20 Health minister Zhang Wenkang and former Beijing mayor Meng Xuenong sacked.
April 23 WHO lifts its travel advisory for Hong Kong
June 11 The last Sars case in Hong Kong reported. Sars infected 1,755 people in the city and killed 299
June 23 WHO declares Hong Kong and the mainland Sars-free.
July 5 Taiwan is the last place removed from WHO's list of infected areas
January 17 Two new Sars cases confirmed in Guangdong. Four more follow in April
May 19 WHO declares the latest outbreak contained. Worldwide, 8,096 cases of the disease were recorded in 26 countries, with