NANNING, Feb. 2 -- South China's Guangxi Zhuang Autonomous Region reported a human case of H7N9 on Sunday, its first this year.

The patient is a 75-year-old man from the city of Liuzhou. He is in critical condition, the regional health department said in a statement.

The man had been in contact with live poultry before he fell sick on Jan. 27, the department said.

Medical workers have disinfected his home and neighborhood, while 16 people who had close contact with him are under observation.

Local health authorities are investigating the source of the infection. They will not rule out the possibility of suspending live poultry trading.

It is the second case in Guangxi since 2009.

China has reported more than 100 human H7N9 cases, including over 20 deaths this year, with Zhejiang and Guangdong most affected.

Health authorities have strengthened H7N9 prevention and control measures including the closure of live poultry markets in some affected cities.