US Developing Bird Flu Vaccine

American scientists are working on a bird flu vaccine amid an outbreak in China that has sickened 14 people and killed 5, according to the Centers for Disease Control and Prevention.

The agency is also assessing the need for new tests to detect the virus, which experts say has mutated to infect mammals.

"All of these actions are routine preparedness measures taken whenever a new novel influenza virus is detected in humans," the CDC said on its website Thursday.

This is the first time avian influenza A viruses, also known as H7N9, have been detected in humans, according to the CDC.

"This is an evolving situation and there is still much to learn," the agency said.

The latest victim of H7N9, a 48-year-old man from Shanghai, is believed to have had direct contact with fowl. His was the sixth confirmed case of bird flu in Shanghai, adding to four in Jiangsu, three in Zhejiang and one in Anhui, according to the Xinhua News Agency.

The World Health Organization said the cases are not linked, but more than 400 close contacts of the infected patients are being monitored as a precaution.

"At this time there is no evidence of ongoing human-to-human transmission," the agency said.

ABC News' chief health and medical editor Dr. Richard Besser said the move by U.S. health officials to ready a vaccine and diagnostic test is a crucial step in preventing an outbreak.

"Whenever there is a new strain of influenza identified that can cause disease in humans, certain steps are taken as part of preparedness," he said. "A rapid response requires early preparedness."

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