A new strain of bird flu has claimed two more lives in China's business capital of Shanghai, taking the total number of human deaths attributed to the H7N9 virus to five, state media said Thursday.
Four of the deaths have occurred in the commercial hub, while the other was reported in the neighbouring province of Zhejiang on Wednesday.
Chinese authorities are trying to determine how exactly the new variety of bird flu infects people, but say there is no evidence yet of human-to-human transmission.
The total number of confirmed cases now stands at 14, including six from Shanghai, according to the official Xinhua news agency which cited health authorities.
The first two deaths occurred in February but were not reported by authorities until late March. Officials said the delay in announcing the results was because it took time to determine the cause of the illnesses.
A 48-year-old poultry transporter was among the latest two reported dead Thursday while the identity of the other person was not released. Both were said to have died a day earlier.
Authorities said none of the eight people whom the 48-year-old had close contact with had shown signs of infection.
The World Health Organisation on Wednesday ruled out the possibility of a pandemic because the sub-type is not thought to be transmitted from human to human, unlike the more common H5N1 strain.
But health experts have emphasised the need to quickly identify the source of the virus and its mode of transmission to reduce human exposure.
China's Ministry of Agriculture said Thursday the virus has been detected in pigeon samples collected at a marketplace in Shanghai, according to a Xinhua report, which did not define the nature of the samples.
After gene sequence analysis, the national avian flu reference laboratory found the strain of the virus in pigeons to be "highly congenetic with those found on persons infected with H7N9 virus".
The more common strain of bird flu, H5N1, killed more than 360 people globally from 2003 until March 12 this year, according to the WHO.
In another development, a man in the central province of Hunan died from H1N1 (swine) flu on Wednesday, Xinhua reported.
A 2009-2010 swine flu pandemic resulted in over 18,000 deaths worldwide, according to WHO estimates. But the strain, while highly contagious, is not thought to be more lethal than ordinary flu.