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The State Department, citing an Al Qaeda threat, warned tourists Friday to stay clear of Western-affiliated buildings, public transportation systems and tourist sites in the Middle East, North Africa and parts of Asia.

"Terrorists have targeted and attacked subway and rail systems, as well as aviation and maritime services," the statement read. “U.S. citizens should take every precaution to be aware of their surroundings and to adopt appropriate safety measures to protect themselves when traveling."

While it’s unclear the exact nature of the threat,  international security expert Michael Kay,  told Fox News that such precautionary measures have become increasingly common in the aftermath of the Sept. 11 --  and after the more recent attack in the Libyan city of Benghazi that killed Ambassador Chris Stevens and three other Americans.

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“Ever since 911, we have been getting used to operating in heighten-threat environments,” he told Fox News. He added that the, “State Department does have a responsibility to U.S. citizens to those traveling aboard,” and that the threat should be taken seriously.

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A worldwide travel alert can be pretty unsettling news for some travelers who find themselves aboard on business or pleasure.  So what can you do to stay safe?

The State Department suggests travelers to sign up for alerts through its Smart Traveler Enrollment Program (STEP) program that gives them latest security updates and information about the nearest embassy.  In addition, travelers should avoid risky behavior, such as joining large crowds or protests, or engaging in activities that might get them noticed.

Security advisor Chris E. McGoey, who advises international businesses and executives traveling abroad, says travelers going to many of these countries (see more information here) are likely aware of the inherent risks associated with these places, and if they’re well prepared, should already have flexible travel plans.

“All tourist or business travelers visiting high-risk areas should have made contingency plans for trip interruption or cancellation,” he says. “Travelers should avoid non-changeable airline tickets and should have enough resources to make quick decisions without concern for expense reimbursement.”

These alerts can have a greater impact on travel in general, he says, as organized tours sometimes cancel the itinerary mid-trip and bring the entire group home. The best advice is to make sure you stay in constant contact with your tour operator, hotel or on-the-ground contact.

McGoey also says be prepared for possible flight delays or changes. August is a popular month for U.S. flights making international trips. According to the Bureau of Transportation statistics, August had the second most international passenger flights on U.S. carriers, after July.

“Following a major travel alert is that airline flights tend to get booked up to major destinations.  The solution is to find your way to another city and book and intermediate flight to a safe country where there are plenty of good connections.”

If a security threat arises, travelers should make quick decisions to get to a safe place, either by flying or driving to a nearby stable city or country, he says.

“Most threats don’t affect individual tourists as long as you avoid demonstrations and risky behavior,” McGoey says.