The impacts of the US' worldwide travel alert

The U.S. State Department issued a "worldwide travel alert" late on Monday due to increased terrorist threats, in the latest security red flag for global tourism.

It warned of the likelihood of terror attacks continuing as members of the so-called Islamic State (ISIS) returned from Syria and Iraq. It noted that attacks had taken place across the world over the past year, including in France, Nigeria, Denmark, Turkey and Mali.

The "alert" holds until February 2016 and follows the terrorist attacks in Paris on November 13 that killed 130 people.

The State Department warned that people should be particularly cautious at festivals and events, as Americans prepare for the holiday season, with Thanksgiving this Thursday.

It issued a lower level "worldwide caution" in both January and July.

"Coming right at the beginning of the holiday season, and on the back of ongoing states of emergency in France and Belgium, (this warning) is surely a hit to confidence," Ian Bremmer, founder of political risk firm, Eurasia Group, told CNBC on Tuesday.

He added that with presidential elections looming in 2016, security concerns could impact candidates' gamesmanship and the country's future policy.

"The bigger long term issue is the impact on elections, where security and foreign policy issues are crowding the top of the agenda. Candidates on both sides of the spectrum will have to show their toughness if they want to succeed in that environment, (it) can absolutely impact the eventual policy trajectory of the country."

Sandra Carvao, chief of communications and publications at the United Nations World Tourism Organization (UNWTO), was optimistic on Tuesday that any resulting hit to tourism from the Paris attacks and their aftermath would be short-lived.

"We have seen over and over that whenever there is that with these kinds of incidents, recovery time tends to be quicker and quicker each time," she told CNBC.

"I think people are more and more informed and that makes a difference… they might have a moment of 'wait and see' but after that they will resume their normal travel patterns."

More than 1.1 billion tourists traveled abroad in 2014, up 4.7 percent on the previous year, according to the UNWTO. International tourism receipts reached a record $1.2 trillion during the year.

In recent decades, Carvao said that tourism at the global level had only decreased in three instances — once after the September 11 attacks in 2001, during the SARS crisis of 2003 and following the global economic crisis in 2009.

"In all the other years, we have had geopolitical situations, we have had global threats and still international tourism has continued to grow… The following year (after the dips mentioned above) always sees a strong recovery," she told CNBC.

Even a short-term dip in foreign tourism from the U.S. could be hard felt, however, with the country the second-largest spender in international tourism after China, spending $110.8 billion in 2014, according to the UNWTO.

With Paris one of the world's most popular tourist destinations, France's tourism industry and broader economy could suffer a lagged impact from the attacks in the city, economists have warned.

Francois Cabau, an economist at Barclays, estimates that the attacks could knock 0.1-0.2 percentage points off French growth in the fourth quarter. He said that the next useful indicator of the economic situation in France would be the December INSEE business confidence report.

This indicator came in at a stable 102 in November on Tuesday, with the large majority of responses registered before the attacks of November 13. The long-term average is 100.

Flight bookings to Paris collapsed in the week following the terrorist attacks, according to ForwardKeys. The travel data analysis firm said that net bookings — taking into account both daily bookings and cancellations — were 101 percent down on the same period last year.

The biggest drops in bookings were from the U.S., China, Spain and Italy.

ForwardKeys said there had been particularly high number of cancellations for the days in the runup to the international climate talks, called COP21, in Paris, in December. France has committed to holding the talks, despite fears that they could be targeted for more attacks.

The number of cancellations appeared to be leveling off, ForwardKeys said, but new reservations were slow.

"The tragic events in Paris are having a strong impact on travel to the city and our data shows that this is continuing in the runup to the normally busy Christmas period. The cancellation period has ended, meaning that the storm is behind us, but booking trends are not yet showing signs of recovery," Olivier Jager, CEO of ForwardKeys, said in a report on Tuesday.

Tourism contributed 77.1 billion euros ($82.1 billion) or 3.6 percent of total French gross domestic product (GDP) in 2014, according to the World Travel & Tourism Council.

France clocked up the most international tourism arrivals — 83.7 million — in 2014 of any country in the world, according to the UNWTO.

Egypt's ancient history, beach resorts and year-round warmth make it a popular destination for European and Russian tourists, with over 900,000 Britons visiting each year, according to the U.K. government.

However, regular flights to and from the U.K. and Sharm el-Sheikh remain suspended, following the crash of a plane flying from the beach resort to St. Petersburg. The investigation into the crash is ongoing, but Russian authorities have stated that it was caused by an explosive device onboard the flight. The so-called Islamic State has claimed responsibility.

U.K. budget airline, easyJet has cancelled all flights to and from Sharm el-Sheikh until January 6, 2016 and British Airways has cancelled flights until January 14, according to media reports.

In addition, the U.K. government has advised against all but essential travel to a large proportion of the country and no travel at all is advised to the area bordering Israel.

"Terrorists continue to plan and conduct attacks in Egypt… There have been threats to western nationals, institutions, and businesses posted on websites and social media. Foreigners could be targeted in tourist resorts or other places. Attacks could be indiscriminate and may occur without prior warning," the U.K. government says on its website.

— By CNBC's Katy Barnato. Follow her on Twitter @KatyBarnato.

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