Taiwan yesterday confirmed an H7N9 bird flu infection in a Taiwanese traveller from Suzhou - the first time the killer virus has spread from the mainland.
The 53-year-old man, who is in critical condition, tested positive after returning to Taiwan via Shanghai on April 9, the island's Centre for Disease Control said. He had not been in contact with birds and poultry.
The discovery may lead to increased scrutiny of travellers to and from the mainland, where the new strain was discovered last month. A total of 108 cases have been confirmed in seven provinces, and 23 have died.
Professor David Hui Shu-cheong, director of the emerging infectious disease centre at Chinese University, said the case in Taiwan meant Hong Kong had to be more cautious, but he said the current measures by the city's government at border check points, including temperature scans and immediate quarantine for visitors with symptoms, were good enough.
"There's no need for panic unless there are human-to-human transmissions," said Hui.
Speaking after a five day study on the mainland yesterday, a panel of World Health Organisation experts described the strain as "one of the most lethal" of its kind and said it was more easily transmissible to humans than an earlier strain, H5N1.
Keiji Fukuda, the WHO's assistant director-general for health security, said: "The situation remains complex and difficult and evolving."
The experts said the most mystifying aspect of the latest virus was the absence of visible illness in poultry, and that this virus was more easily transmissible from poultry to humans than the H5N1 bird flu virus.
A health spokesman in Hong Kong said more staff would be deployed to run health inspections at check points during the Labour Day holiday next month.
View H7N9 map  in a larger map
Click on each balloon for more information on individual patients infected: blue, patients infected with the H7N9 virus under treatment; red, those infected with H7N9 who have died; yellow, those who have fully recovered; and pink, those infected other types of the Influenza A virus, including H1N1.