Bird Flu Crosses Strait to Taiwan A Taiwanese man is in severe condition after contracting the deadly H7N9 strain.

April 24, 2013 -- A Taiwanese man has contracted a deadly strain of bird flu once confined to mainland China, health officials said today.

The man, 53, is thought to have imported the H7N9 virus to his native Taiwan after travelling to China's Jiangsu Province, where bird flu has sickened at least 24 people and killed three, according to the Chinese Center for Disease Control and Prevention. He is said to be in "severe condition."

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The latest case has lifted the tally of virus victims to 109, 22 of whom have died, according to the World Health Organization. It has also flamed fears that the deadly virus could spread beyond East Asia.

"Given the extent of global travel, I expect that we will see cases in the United States," ABC News chief health and medical editor Dr. Richard Besser said. "It's so important that people who become ill tell their doctors if they have been traveling."

The Taiwanese man developed flu symptoms April 12, three days after returning to Taiwan from Shanghai, health officials said. He was hospitalized four days later. But initial tests for H7N9 were negative, with official confirmation from Taiwan's National Influenza Center coming more than two weeks after his trip April 24.

"Physicians are once again reminded to report suspected cases to the health authority within 24 hours of detection according to the relevant regulation," the Taiwanese CDC said in a statement, noting that suspected cases with severe respiratory infections should be hospitalized in isolation.

The H7N9 virus is thought to pass from birds to humans. But many of its victims, including the Taiwanese man, reported no contact with birds, and few birds are testing positive for the disease.

"There are so many unanswered questions about this disease," Besser said. "Could there be another route of transmission? Are some people becoming infected from exposure to infected people?"

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Taiwan's Central Epidemic Command Center has obtained a list of 139 people who came into contact with the Taiwanese man, including 110 health care workers. Three health care workers who developed symptoms of an upper respiratory infection are being closely monitored, health officials said.

WHO spokesman Gregory Hartl last week said there was no evidence of "sustained human-to-human transmission," adding that "the only instances where there might have been human-to-human transmission are between two close family members."

"The main thing now is to figure out how this virus spreads and where it lives," Hartl said. "Until then, we're shooting in the dark."

In the meantime, Taiwanese health officials are urging travelers to mainland China to avoid direct contact with birds or their droppings, consume only thoroughly cooked poultry and eggs, wash their hands often and wear a protective mask.

U.S. health officials are also bracing for bird flu by preparing a vaccine, a process expected to take six months. In the meantime, they, too, are urging travelers to China to steer clear of birds, practice good hygiene and report any and all flu-like symptoms to a doctor upon return.

"The CDC has developed a diagnostic test for H7N9 flu so that travelers who develop symptoms can be tested," Dr. Besser said.

U.S. doctors are urged to promptly report suspected bird flu cases to their state health departments.