Last year Chinese farmers noticed their prized birds were producing fewer eggs than usual, and egg production plummeted by as much as 90 percent in some flocks. Ducks were waddling about awkwardly, their coordination hampered, and eating less than usual. Some died within days.
By the end of the year some 4.4 million ducks in the eastern provinces of Fujian, Shandong and Zhejiang, where duck farming is common, had caught the mysterious illness, AAAS ScienceMag.org reported Tuesday.
Scientists at the Chinese Academy of Sciences in Beijing analyzed the affected animals and discovered an aggressive new flavivirus, a class of viruses that includes those that cause yellow and dengue fevers.
It was the first flavivirus ever identified in ducks.
In addition to potentially affecting Chinese duck farming and the economy that depends on it, the flavivirus could put humans at risk, researchers said.
"Most flaviviruses are zoonotic," meaning they can be transmitted from animals to people, microbiologist George Gao of the science academy said, "so infection of human beings cannot be ruled out."
Because of the pervasiveness of duck farming in China, Gao said, the disease should be closely monitored, in part because it could spread to people.