A third human H5N6 avian flu case has been reported in south China's Guangdong Province within two weeks, local health authorities said Thursday.

The new patient is a 25-year-old man from Longgang District in the city of Shenzhen, the provincial health bureau said in a press release.

The man, surnamed Cai, is in a serious condition and being treated in a hospital in Shenzhen, it said.

It is the second H5N6 case in Shenzhen. The first patient died on Dec. 30. Gene analysis of a sample from the 26-year-old woman indicated her infection was from contact with live poultry or a poultry market.

A 40-year-old woman in the city of Zhaoqing was also reported to be suffering from the virus and in a serious condition.

Guangdong has reported four H5N6 infections in total, with the first in the provincial capital of Guangzhou in December 2014.

The world's first human H5N6 infection was reported in May 2014 in southwest China's Sichuan Province.