Shu Yuelong, from the National Centre for Disease Control and Prevention, said China needed to work harder at preventing bird flu outbreaks. The warning came after the health ministry said a 16-year-old boy had died in central Hunan province.The human form of bird flu has now claimed three lives this year.
Experts fear that an upsurge in cases could lead to the mutation that will allow human-to-human transmission - which could herald the start of a global pandemic.
The northern hemisphere winter and spring are peak bird flu times, and in China, millions of people head home for the Chinese New Year, which could lead to massive spread of the virus.
On Monday, the authorities announced that a woman in eastern Shandong province had died from bird flu. And two weeks ago, a 19-year-old woman died in Beijing after handling ducks.
Meanwhile, a two-year-old toddler reported to have been in critical condition with the H5N1 virus has now recovered and is described as "stable". Chinese and Hong Kong media have been reporting that the toddler's mother had died this month after exhibiting symptoms similar to bird flu, but her death has not been officially blamed on bird flu.
Consumers in Hong Kong have been warned not to eat poultry that originates from the mainland of China.
China's ministry of agriculture said on Sunday that no bird flu epidemics were detected in Shanxi and Henan provinces after the two-year-old's infection was confirmed. This is leading experts to worry that the virus has changed, since human infections are usually seen after a bird flu outbreak among poultry. There are also concerns that some chickens may carry a sub-clinical form of the disease and not show any symptoms, but still be infectious.
China has the world's biggest poultry population and is seen as critical in the fight to contain the H5N1 strain of the virus, which resurfaced in Asia in 2003, killing at least 247 people.
H5N1 does not transmit easily to humans but experts fear it could mutate and cause a worldwide pandemic.
