GUANGZHOU - South China's Guangdong province reported its third H7N9 human infection of this year on Wednesday, with health authorities warning that the province has entered a high-incidence period for bird flu.

A 56-year-old man in the city of Zhaoqing was confirmed to be infected with the H7N9 virus Wednesday, the provincial health and family planning commission said in a statement.

The man is in critical condition at a local hospital, it said.

Guangdong, which borders Hong Kong, reported this year's first and second H7N9 human cases on Monday and Tuesday in the cities of Shenzhen and Dongguan. The Guangdong disease control and prevention center said the province has entered the bird flu's high-incidence period, which occurs in winter and spring, and that risks exist for occasional human infections.

Authorities in Guangdong and Hong Kong last week culled thousands of chickens after Guangdong's poultry exports to Hong Kong were found to be infected with the virus.

Hong Kong raised its response level in hospitals to "serious" from "alert" after a 68-year-old woman was hospitalized on Dec 25 with H7N9, the region's first case since early 2014. The woman had arrived from Shenzhen two weeks earlier.