>> RELATED: State Department issues Worldwide Travel Alert for U.S. citizens

1. Why was the alert issued? According to a statement posted on the State Department's website, "Current information suggests that ISIL (aka Da'esh), al-Qaida, Boko Haram and other terrorist groups continue to plan terrorist attacks in multiple regions."

The statement adds, "Authorities believe the likelihood of terror attacks will continue as members of ISIL/Da'esh return from Syria and Iraq. Additionally, there is a continuing threat from unaffiliated persons planning attacks inspired by major terrorist organizations but conducted on an individual basis."

The alert mentions recent attacks in France, Nigeria, Denmark, Turkey and Mali, as well as the downing of a Russian passenger jet in Egypt.

2. What does this mean for travelers? Officials urge Americans to "exercise vigilance when in public places or using transportation" and "avoid large crowds," particularly during the holidays and at holiday events.

"U.S. citizens should monitor media and local information sources and factor updated information into personal travel plans and activities," the alert says, instructing anyone with "specific safety concerns" to contact law enforcement. The statement also advises Americans to do the following:

  • Follow local authorities' instructions;
  • Expect increased security screenings;
  • Talk to family members and make sure they have your contact information;
  • Sign up for the Smart Traveler Enrollment Program (STEP), which provides safety updates and helps the U.S. Embassy, family and friends contact you during an emergency.

3. How long is this travel alert in effect? It expires Feb. 24, 2016.

4. What are officials doing to protect against possible threats? "Foreign governments have taken action to guard against terrorist attacks, and some have made official declarations regarding heightened threat conditions," the statement says, adding that authorities are working to "conduct raids and disrupt terror plots." 

5. How can I get more information? Visit the State Department's website to learn about travel alerts and warnings or sign up for STEP. You also can call 1-888-407-4747 from the United States and Canada or 1-202-501-4444 from other countries from 8 a.m.-8 p.m. ET Monday-Friday. In addition, the department provides updates on its Twitter and Facebook pages.