Despite highly cautious countermeasures, the number of A/H1N1 flu cases in China may rise dramatically in the future, said a leading expert.

Once the virus enters a country, it begins to spread internally, said Scott Dowell, director of the Global Disease Detection Program at the US Center for Disease Control and Prevention in Atlanta.

"We anticipate there will be domestic transmission of the virus in China like in other countries including Canada, Panama and Japan," he said.