Last year, U.S. researchers reported that ducks in Southeast Asia had begun carrying the bird flu virus without showing symptoms. Now, scientists in Vietnam have found numerous asymptomatic cases in the country's vast chicken population, according to Nguyen Tran Hien, director of the National Institute of Hygiene and Epidemiology. "It seems that the virus may adapt in humans and in poultry a little bit. Therefore, the symptoms are not as severe as before," Hien said. "Also, the transmission may be faster and easier."
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