April 2021 was a unique month for U.S. State Department travel advisory updates as the DOS issued an update for every country around the world as part of an effort to “rely more on the Centers for Disease Control and Prevention’s (CDC) existing epidemiological assessments.” The result was the expansion of the department’s Level 4 “Do Not Travel” guidance to about 80 percent of countries worldwide. While Americans will want to familiarize themselves with the latest updates for any destination they’re planning to visit this summer, here are 15 notable pieces of advice travelers won’t want to miss.