Parts of Bangladesh, India, Indonesia, the Philippines and Vietnam are at risk because, like China, they have live bird markets in densely-populated areas, the team said.
Places potentially at risk include urban centres on the coast of east and southeast China where H7N9 has not been reported, parts of the Bengal regions of Bangladesh and India, Vietnam's Red River and Mekong deltas; and isolated areas of Indonesia and the Philippines.
H7N9 is the second bird virus alongside H5N1 to have emerged in recent years through live markets, where traders and shoppers come in close contact with infected chickens and ducks.
H5N1 is far more dangerous for humans than H7N9 but its spread through birds is more easily detectable, as poultry usually show signs of being sick from it.
H7N9 can be asymptomatic in birds, meaning the animals may show no sign of illness.
"The slow geographical expansion of the reported H7N9 cases in the central and southern provinces of China indicates that despite remarkably strict control efforts, H7N9 is difficult to contain along poultry market chains," the study warned.
The study was led by scientists at the Free University of Brussels, the International Livestock Research Institute, Oxford University and the Chinese Centre for Disease Control and Prevention.
Looking at the evidence from northeastern China, where chicken production is intensive, the researchers said industrial-scale farms were unlikely to have played a significant role in spreading H7N9 there.
This backs previous research that smaller farms, where domestic fowl are likelier to come into contact with wild birds, and trading in infected poultry at local markets were major channels for spreading the virus.