BEIJING — The new strain of avian influenza that has infected more than 100 people in China in the last two months has, for the first time, been reported outside mainland China.

Officials in Taiwan reported one case in a 53-year-old Taiwanese citizen who traveled regularly to the Chinese city of Suzhou for work, where he probably contracted the virus. He fell ill on April 12, three days after returning to Taiwan. Tests revealed on Wednesday that he was infected with the H7N9 bird flu virus. As of Tuesday, Chinese officials had reported 108 cases and 22 deaths from the new flu.

The case has set off alarms in Taiwan, where the Central Epidemic Command Center says that it has “continued to strengthen surveillance and fever screening of travelers arriving from China.”

The patient in Taiwan, described as severely ill, is being treated in a special isolation room, and 139 people who had contact with him — including 110 health workers — are being watched for symptoms. So far, there is no evidence that any have contracted the disease, which has not been found to spread from person to person.