Technicians wearing protection suits begin to cull poultry at Huhuai poultry wholesale market, where the H7N9 bird flu virus was detected in pigeon samples, in Shanghai April 5, 2013. Chinese authorities slaughtered over 20,000 birds on Friday at this poultry market in the financial hub Shanghai as the death toll from a new strain of bird flu mounted to six, spreading concern overseas and sparking a sell-off on Hong Kong’s share market. REUTERS/Stringer (CHINA – Tags: HEALTH DISASTER ANIMALS)