International tourism thumb|International tourist arrivals per year by region International tourism is tourism that crosses national borders. Globalisation has made tourism a popular global leisure activity. The World Tourism Organization defines tourists as people "traveling to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes". The World Health Organization (WHO) estimates that up to 500,000 people are in flight at any one time.Swine flu prompts EU warning on travel to US. The Guardian. 28 April 2009.
International tourism thumb|International tourist arrivals per year by region International tourism is tourism that crosses national borders. Globalisation has made tourism a popular global leisure activity. The World Tourism Organization defines tourists as people "traveling. to and staying in places outside their usual environment for not more than one consecutive year for leisure, business and other purposes". The World Health Organization (WHO) estimates that up to 500,000 people are in flight at any one timeSwine flu prompts EU warning on travel to US. The Guardian. 28 April 2009.