Chinese authorities say a teenager has become the country's fourth person to be diagnosed this year with bird flu, just days after a second fatality in less than a month.

A statement posted on the Ministry of Health Web site says the 16-year-old boy from the southwestern province of Guizhou fell ill on January 8.

On January 16, he was transferred to a city in neighboring Hunan province.  His condition has since worsened and is now critical.

The news comes just two days after a 27-year-old woman died of bird flu in the eastern province of Shandong.

The official Xinhua news agency says the national disease center confirmed she had the deadly H5N1 strain of bird flu.

In addition to that case, China's health ministry says a two-year-old girl is critically ill after testing positive for the H5N1 strain.  Officials say the girl was taken to a hospital in her home province of Shanxi after falling ill January seventh in central Hunan province.

Earlier this month, a 19-year-old woman died of bird flu in Beijing after handling ducks she bought at a market.  

Chinese authorities have stepped up their monitoring of the sale of live poultry in the run-up to the Lunar New Year holiday, which begins next Monday.

The government has warned that the approach of the holiday - and an increase in the sale and movement of poultry - brings a higher risk of the emergence of an epidemic.

The World Health Organization says bird flu has killed 248 people since it resurfaced in Asia in 2003, including 21 in China.  The death of the 27-year-old woman on Saturday raises China's toll to 22.