The patient, a 39-year-old man living in Shenzhen, developed symptoms on December 21 and was admitted to a hospital on December 25 because of severe pneumonia, the Centre of Health Protection of Hong Kong said in a statement. He is now in critical condition.
China's Ministry of Health said preliminary laboratory tests on the patient's specimen by the Centre for Disease Control and Prevention of Guangdong Province had yielded a positive result for H5N1.
About 10 days ago Hong Kong culled 17,000 chickens at a wholesale poultry market and suspended all imports of live chickens from mainland China for 21 days after a dead chicken there tested positive for the H5N1 virus.
The virus is normally found in birds but can jump to people who do not have immunity to it and researchers worry it could mutate into a form that would spread around the world and kill millions of people.
In recent years, the virus has become active in various parts of the world, mainly in east Asia, during the cooler months.
Authorities in China are especially worried about the spread of infectious diseases around this time when millions of Chinese travel in crowded buses and trains across the country to go home to celebrate the Lunar New Year.
The current strain of H5N1 is highly pathogenic, kills most species of birds and up to 60 percent of the people it infects. Since 2003, it has infected 573 people around the world, killing 336. The virus also kills migratory birds but species that manage to survive can carry and disperse the virus to new, uninfected locations.
The virus can kill birds and humans in a matter of days but can survive far longer durations in a moist, cool environment.
It transmits less easily between people but there have been clusters of infections in people in Indonesia and Thailand in the past, where the virus is believed to have been passed between family members through direct contact with contaminated respiratory secretions.
(Reporting by Alison Leung; Editing by Alessandra Rizzo)
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