Pigeons became a source of concern after one in Shanghai was found infected with the new H7N9 strain, according to reports.



At least 31 people have been infected with the killer strain while 9 of them have died in the outbreak.



Among the new cases, several from Shanghai, Jiangsu and Zhejiang provinces, with at least one of whom is dangerously ill, Chinese news agencies have said.



The Hangzhou Carrier Pigeon Association said this week that it will use a different flu vaccine in the vaccination drive since none exists for H7N9.



State media has quoted authorities as saying a vaccine could take months to produce.



Many Chinese are skeptical of the government's pronouncements about the H7N9 virus given a history of public health scandals and cover-ups, according to reports.



The government initially tried to conceal an outbreak of Severe Acute Respiratory Syndrome (SARS), which emerged in China in 2002 and killed about one in 10 of the 8,000 people it infected worldwide.