By Emma Nitzsche 

On August 2, the U.S. Centers for Disease Control and Prevention (CDC) added sixteen new destinations to its highest COVID-19 warning level. Popular travel locations included Greece, Ireland, and the U.S. Virgin Islands.

The advisories are based on a scale of increasing severity, including Low (1), Moderate (2), High (3), Very High (4), and Unknown. Destinations are classified as a “Level 4” if there are 500 COVID-19 cases per 100,000 people in the past 28 days.

The “Level 4” risk countries included Greece, Ireland, Kazakhstan, Lesotho, Libya, Malta, Martinique, Saint Barthelemy, and Saint Martin. According to Reuters, new “Level 3” destinations include Denmark, Canada, Switzerland, Thailand, Russia, Iceland, France, and Morocco.

All international travelers who fly into the U.S. are required to get tested for Coronavirus within three days of boarding a flight. This testing policy is across the board, even if travelers have received the vaccination. Certain U.S. territories, including Puerto Rico, the U.S. Virgin Islands, American Samoa, Guam, and the Northern Mariana Islands, are exempt from return testing requirements.

“International travel poses additional risks, and even fully vaccinated travelers are at increased risk for getting and possibly spreading new COVID-19 variants,” the agency warns. “CDC recommends delaying international travel until you are fully vaccinated.”

Federal restrictions have already begun in Greece, which opened to American tourists in May. According to the World Health Organization. Greece has reported more than 18,000 new cases each week for the past several weeks. Reuters reported that a little over half (53.4%) of Greece’s population had received at least one dose of the vaccine.

Additionally, Mykonos implemented a curfew and banned music in restaurants, cafes, and clubs. The European Centre for Disease Prevention and Control has warned against visiting the country’s south Aegean Islands, including Mykonos and Santorini.

The new CDC updates come as the U.S. starts cracking down on the COVID-19 delta variant. There had already been some travel restrictions for U.S. travelers due to the pandemic. Still, the uncertainty of the delta variant has led the White House to keep the existing COVID-19 travel restrictions in place.

“Driven by the delta variant, cases are rising here at home, particularly among those who are unvaccinated, and appears likely to continue in the weeks ahead,” White House press secretary Jen Psaki said after the CDC set the United Kingdom as a “Level 4” risk country.

The delta variant was identified initially in India but has since spread around the world. U.S. health officials said the delta variant accounts for an estimated 83% of the nation’s coronavirus cases.