Travellers carry their luggage at the arrivals terminal in Israel’s Ben Gurion International Airport, amid a spread of the Delta variant of the coronavirus disease (COVID-19), near Tel Aviv, Israel July 8, 2021. REUTERS/Amir Cohen

Israel warned on Tuesday against travel to the United States and other countries and said it would tighten quarantine measures for inbound travelers as part of efforts to slow the spread of the coronavirus Delta variant.

New COVID-19 cases have surged in highly-vaccinated Israel since the emergence of the highly contagious Delta variant, prompting health officials this week to begin administering vaccine booster shots to people over 60.

It also began mandating isolation for returning travelers — including those vaccinated or recovered from the virus — from countries deemed “red,” indicating a rapid spread of the disease.

On Tuesday, the health ministry said it would add 18 countries to its red list, including the United States, France, Italy, Iceland, Greece and others.

“Beginning August 11, 2021, complete isolation for all age groups is required, even for the vaccinated and recovering,” the health ministry said of the 18 countries, warning of “a significant increase in morbidity coming from abroad.”

The Delta variant has caused a resurgence in coronavirus cases across the United States. Florida and Louisiana were at or near their highest hospitalization numbers of the coronavirus pandemic on Monday.