Entry-exit inspection and quarantine authorities across China found nearly 7,000 confirmed flu cases from inbound passengers in December and January, an increase of 81.9 percent compared with the same period for December 2016 and January 2017, China’s top authority for port inspection and quarantine said on Friday.

Flu activity has gained momentum since the end of last year in many countries and regions in the Northern Hemisphere, which has brought increasing risk of flu infection to China, the General Administration of Quality Supervision, Inspection and Quarantine said in a release.

With the arrival of the Spring Festival holiday and winter vacations for schools, an increasing number of Chinese are going overseas for tourism, the administration said, advising passengers to take enough precautionary measures to prevent infection.

Tourists bound for regions with flu outbreaks such as the United States, Canada and Italy are advised to receive flu vaccines and wear a mask if necessary.

Inbound tourists should notify Chinese inspection and quarantine authorities if they display syndromes such as fever and cough, the administration said.