NEW: Authorities slaughter market birds in Shanghai after H7N9 found in pigeons
Poultry markets in Shanghai will close starting Saturday
Fourteen human cases of H7N9 have been reported in eastern China so far
No cases of human-to-human transmission virus have been confirmed
Chinese authorities have killed more than 20,000 birds from a live-poultry trading zone in Shanghai after an unusual strain of bird flu that has so far killed six people in the country was found in pigeons on sale in the city, state-run media outlet Xinhua reported Friday.
Details of the slaughter of chickens, ducks, geese and pigeons