Japan confirmed its first case of infection from the mystery Wuhan pneumonia-like virus yesterday, as Vietnam said it has isolated two visitors from the Chinese city as a preventive measure.
The Japanese health authorities said a resident in his 30s, from Kanagawa prefecture, south of Tokyo, had tested positive for the new virus strain. But officials stressed that this was an isolated case, and that nobody else in Japan is suspected of being infected.
"It has not been confirmed that sustained human-to-human infections can occur," Chief Cabinet Secretary Yoshihide Suga said.
The man, a Chinese national, had been in close contact with a patient when he was in Wuhan, the Health Ministry said. It added that none of the man's family members who live with him in Japan, nor the doctors who treated him, have tested positive for the virus.
The Wuhan virus outbreak coincides with the annual flu season in Japan, and the ministry has reiterated its advisory for people to wash their hands, gargle, and wear masks to avoid falling sick.
Meanwhile, two Chinese tourists with fever symptoms from Wuhan were quarantined by Vietnam's Ministry of Health and are under observation, after they landed at Danang International Airport on Tuesday. Hanoi sent a medical team to the coastal city and called an emergency meeting on Wednesday on prevention efforts.
Japan's is the second confirmed Wuhan virus case to be reported outside China, after Thailand confirmed on Monday that a 61-year-old Chinese woman had been hospitalised last week for high fever and breathing difficulties. She is now in a stable condition.
The Kanagawa resident had developed fever symptoms on Jan 3, when he was in Wuhan. He returned to Japan on Jan 6, but was not detected at the immigration health checkpoint as his fever had been brought down by medication.
He saw a doctor later the same day and reported his travel history to Wuhan, but was prescribed medication and could return home as his symptoms were relatively minor.
He went to a hospital on Jan 10 as his fever persisted and was warded until Wednesday.
Later that evening, Japan's National Institute of Infectious Diseases, which had prepared diagnostic kits after China shared the genetic sequence of the coronavirus on Sunday, confirmed that the man had been infected with the new coronavirus strain.
There has been growing regional concern over the outbreak of pneumonia in Wuhan that has been linked to a new coronavirus strain.
The family of pathogens is behind diseases ranging in severity from the common cold to the severe acute respiratory syndrome (Sars), which killed hundreds in Asia in 2002 and 2003.
Coronaviruses cause symptoms like those of the common cold, and are spread through sneezing, coughing, or direct contact.
Many of the 41 reported cases in Wuhan were traced to the Wuhan Huanan Seafood Wholesale Market. But the patients in the Thai and Japanese cases had not visited the market, which has been closed since Jan 1 to contain the outbreak.
No new cases have been reported in Wuhan since Jan 3. One person has died, while at least seven patients were treated and discharged.
The World Health Organisation (WHO), which says the virus has "some limited human-to-human transmission", has warned of a potential wider outbreak.
There were 78 suspected cases in Hong Kong as of yesterday, of whom at least 66 have been discharged. There have also been suspected cases in Taiwan, South Korea and Singapore.