The Food and Agriculture Organization (FAO) warned that countries neighbouring China were at "high risk" of exposure.
The Food and Agriculture Organization (FAO) warned that countries neighbouring China were at "high risk" of exposure to the H7N9 strain, which has recently mutated to become far more deadly for chicken than it had been.
The agency also warned that wild birds could carry the strain of the virus to Europe and the Americas, adding that it was baffled as to why China's efforts to contain the outbreak had not worked as well as anticipated.
The FAO's statement came after China reported last month that 79 people had died in January alone, the deadliest H7N9 outbreak since the strain first appeared in humans in 2013.
Nearly one in three people who contract H7N9 die from it.
FAO said the recent surge in cases in eastern and southern parts of China meant the virus had caused more reported human cases than all other types of avian influenza viruses, such as H5N1 and H5N6, combined.
Vincent Martin, the FAO's representative in China, said efforts to contain the outbreak needed to focus on eliminating the strain at its source.
"Targeted surveillance to detect the disease and clean infected farms and live bird markets, intervening at critical points along the poultry value chain -- from farm to table -- is required," he said.
"There should be incentives for everybody involved in poultry production and marketing to enforce disease control."
The agency recognised that China had invested heavily in surveillance of live bird markets and poultry farms while noting that monitoring has "proven particularly challenging as until recently (the strain) has shown no or few signs of disease in chickens."
The organisation said new evidence from Guangdong in southern China pointed to H7N9 having mutated to become much deadlier for chickens while retaining its capacity to make humans severely ill.
This could make it easier to spot outbreaks, as infected chickens are typically dying within 48 hours of infection, but it also underscores the potentially huge economic implications of the mutation, FAO said.
The FAO emphasised that there was no risk of humans catching the potentially deadly influenza strain by eating chicken.
China has suspended trade in live poultry in several cities, urged consumers to switch to frozen chicken, enforced stricter hygiene standards in fresh food markets, and culled affected flocks.
"With all the efforts taken by China and partners, there is a pressing need to understand why these measures have not worked as well as expected," the FAO said.