Singapore: New cases of H7N9 being reported from China's Guangdong province has raised the number of people infected by the deadly virus to 25. According to reports by a leading China news paper, health experts have waned that the Guangdong province, which borders Hong Kong, has entered the high-incidence phase for bird flu, which usually emerges in winter and spring.

Thousands of chicken have been culled in China and Hong Kong amid bird flu scare this year. Health authorities in Guangdong said that measures have been taken to curb the spread of the disease. In addition to Guangdong, Shanghai, Fujian, Jiangxi and Zhejiang areas in east China have reported human cases of H7N9 this winter.

WHO describes H7N9 as an unusually dangerous virus for humans which is more easily transmitted from poultry to humans than H5N1. First human infection of H7N9 was reported in March 2013.

Right from its discovery, H7N9 has caused a global concern owing to its possible transmission to humans and the threat of a pandemic if it mutates to a form that can be easily passed from birds to humans and then, from human to human.