Bird flu infection rates on Chinese poultry farms may be far higher than previously thought, because the strain of the deadly virus that has killed more than 100 people this winter is hard to detect in chickens and geese, animal health experts say.
Poultry that have contracted the H7N9 strain of the avian flu virus show little or no sign of symptoms. That means any infection is only likely to be detected if farmers or health authorities carry out random tests on a flock, the experts said.
But in humans, it can be deadly.