Hong Kong health authorities are taking no chances with a mysterious outbreak of viral pneumonia in the central Chinese city of Wuhan, warning of symptoms similar to Sars and bird flu as they step up border screening and put hospitals on alert.

“The situation in Wuhan is unusual, and we are not sure about the reasons behind the outbreak yet,” said Secretary for Food and Health Sophia Chan Siu-chee said after an urgent night-time meeting with officials and experts on New Year’s Eve. “Since we are now in the holiday season, and Hong Kong has close transport ties with Wuhan, we must stay alert.”

With Wuhan reporting 27 infections so far, Chan said the Department of Health would increase vigilance and temperature screenings at every border checkpoint, including the city’s international airport and high-speed railway station in West Kowloon.

Hospital Authority chief executive Tony Ko Pat-sing said frontline medical staff had been alerted at public and private hospitals.

“So far, there are no suspicious pneumonia cases in public hospitals,” he said. “But once we suspect cases, including the presentation of fever and acute respiratory illness or pneumonia, and travel history to Wuhan within 14 days before onset of symptoms, we will put the patients into isolation.”

Experts from the University of Hong Kong have also been enlisted to conduct faster genetic testing of virus samples.

News of the outbreak in Wuhan came to light after an urgent notice from the city’s health department, which told hospitals to report further cases of “pneumonia of unknown origin”, started circulating on social media on Monday night.

The notice invoked memories of the 2002 and 2003 outbreak of severe acute respiratory syndrome, or Sars, which killed hundreds of people in mainland China and Hong Kong.

Over the past month, 27 patients in Wuhan – most of them stall holders at the Huanan seafood market – have been treated for the mystery illness.

The Wuhan municipal health commission said seven of the patients were seriously ill. Two had nearly recovered and were about to leave hospital, while the remaining patients were in a stable condition. Most patients had fevers and some were short of breath.

The health commission’s initial investigations, which included clinical diagnosis and laboratory tests, suggested all 27 were viral pneumonia cases.

No human-to-human infection had been reported so far, officials said, and no medical staff had contracted the disease. More pathological tests and investigations were underway.

Microbiologist Yuen Kwok-yung from the University of Hong Kong noted similarities with the 1997 outbreak of avian influenza, and the severe acute respiratory syndrome epidemic of 2003 – all cases in Wuhan were linked to the same seafood market, reported in December, and with a severe infection rate of 25 per cent.

“But there’s no need to panic. First, compared with 2003, we have better systems in notification, testing and infection control. We also have medicines that we can try,” Yuen said.

“In the past, we didn’t have proper isolation facilities. If you ask me will there be any chance that the severity will be the same as in 2003, I will say the chance is low. All we have to do is to be on alert.”

The 2003 epidemic infected more than 1,750 people and killed 299 in Hong Kong.

The patients in Wuhan were under quarantine while tests and a disinfection programme were being carried out at the seafood market, the city’s health authorities said.

Qu Shiqian, a vendor at the seafood market, said government officials had disinfected the premises on Tuesday and told stallholders to wear masks.

He said he had only learnt about the pneumonia outbreak from media reports.

“Previously I thought they had flu,” he said. “It should be not serious. We are fish traders. How can we get infected?”

State television reported that a team of experts from the National Health Commission had arrived in Wuhan to lead the investigation, while People’s Daily said the exact cause remained unclear and it would be premature to speculate.

People’s Daily also quoted several hospital sources in the city who said it was likely that the virus responsible was different from Sars, which infected more than 5,300 people and killed 349 in mainland China between late 2002 and mid-2003.

Tao Lina, a public health expert and former official with Shanghai’s centre for disease control and prevention, said that while a return of Sars could not be ruled out, the public health care system was now better able to handle such an outbreak.

“We don’t know whether Sars will come back after 16 years. In human history, we’ve never seen an epidemic disappear forever without the interference of vaccines. So we have reasons to be cautious, but not to panic too much,” Tao said.

“I think we are [now] quite capable of killing it in the beginning phase, given China’s disease control system, emergency handling capacity and clinical medicine support.”