Widespread travel restrictions and the closure of airports and national borders has plunged international tourism into its worst crisis since records began in 1950, the UN body said in a statement.
The number of international tourist arrivals could plunge by 60 to 80 percent in 2020 owing to the coronavirus, the World Tourism Organization said on Thursday, revising its previous forecast sharply lower.
Widespread travel restrictions and the closure of airports and national borders to curb the spread of the virus had plunged international tourism into its worst crisis since records began in 1950, the UN body said in a statement.
Tourist arrivals fell by 22 percent in the first three months of the year and by 57 percent in March alone, with Asia and Europe suffering the biggest declines, according to the Madrid-based organisation.
"The world is facing an unprecedented health and economic crisis. Tourism has been hit hard, with millions of jobs at risk in one of the most labour-intensive sectors of the economy," said the body's secretary-general, Zurab Pololikashvili.
Airlines have suffered the most since the outbreak began with most flights grounded, but hotel groups, cruise operators and tour operators are also reeling.
The UN body said the full extent of the fall in international tourism would depend on how quickly international borders open again.
Under a best-case scenario, with travel restrictions starting to ease in early July, international tourist arrivals could fall by just 58 percent.
If borders and travel restrictions are only lifted in early December, the fall would be more in the order of 78 percent.
If the restrictions are lifted in early September, the UN body predicts a fall of 70 percent.
Under these scenarios, the drop in international travel could lead to a loss of $910 billion to $1.2 trillion in export revenues from tourism, and of 100 to 120 million direct tourism jobs.
While international tourism has taken a hit from the outbreak of disease in the past, the new coronavirus is unprecedented in its geographic spread.
By comparison, international tourism arrivals fell by just 0.4 percent in 2003 after the outbreak of Severe Acute Respiratory Syndrome, which killed 774 people worldwide.
The UN body said most experts believe there will be signs of recovery by the final quarter of 2020, with domestic demand expected to recover faster than international demand. Asia and the Pacific were expected to rebound first, it added.
"Based on previous crises, leisure travel is expected to recover quicker, particularly travel for visiting friends and relatives, than business travel," it added.
The body had forecast at the beginning of the year that international tourism would grow by 3 to 4 percent in 2020, but then revised its forecast at the end of March, predicting a 20 to 30 percent decline.
International tourism arrivals rose by 4 percent in 2019 to 1.5 billion, with France the world's most visited nation, followed by Spain and the US.
The last time international tourist arrivals posted an annual decline was 2009 when the global economic crisis hit the travel sector hard.
The tourism industry accounts for about 10 percent of the world's gross domestic product and jobs.