(CNN) — Two tropical islands half a world apart and popular with tourists -- Jamaica in the Caribbean and Sri Lanka in South Asia -- are now among the highest-risk destinations for travelers.
That's according to the US Centers for Disease Control and Prevention's travel advisories list, which was updated on Tuesday.
Also joining the bulging highest-risk list during a global swell of Delta variant cases is the isolated nation of Brunei on the island of Borneo.
People should avoid traveling to locations designated with the "Level 4: Covid-19 Very High" notice, the CDC recommends. Anyone who must travel should be fully vaccinated first, the agency advises.
How the CDC ranks nations
An aerial view of Kingston, Jamaica. The popular Caribbean island has been hit with a surge of Covid-19 cases recently.
Valery Sharifulin/TASS/Getty Images
The CDC's evolving list of travel notices ranges from Level 1 ("low") to Level 4 ("very high").
Destinations that fall into the "Covid-19 Very High" Level 4 category have had more than 500 cases per 100,000 residents in the past 28 days, according to CDC criteria. The Level 3 category applies to destinations that have had between 100 and 500 cases per 100,000 residents in the past 28 days.
Jamaica's Covid-19 vaccination campaign has had low numbers so far, with only 19 doses given per 100 people as of Tuesday. It has been in a series of curfews since late August with "no-movement" days in hopes of slowing the virus' spread. Sri Lanka has seen a swell in cases recently despite having one of Asia's stronger vaccination campaigns, with 102 doses administered per 100 people as of Tuesday. By comparison, its much larger neighbor India has only given 49 doses per 100 people.
Other popular destinations on Level 4
A view of the Peloponnese in Greece, which is at the CDC's highest risk level.
Some of the most visited vacation spots around the world occupy a spot on the CDC's Level 4 list. That includes Covid-ravaged Brazil, which has occupied a spot there for months. Other popular nations currently considered the highest risk include:
-- The Bahamas
-- Costa Rica
-- South Africa
-- United Kingdom.
You may click here to see all Level 4 nations, plus the other three levels as well.
Level 3: High risk
Also on Tuesday, 10 nations were newly assigned to the CDC's "Level 3: Covid-19 High" category. A big mover popular with the luxury travel set was the little Caribbean resort island of Anguilla.
It had been at "Level 1: Low" and had maintained strict protocols on arriving tourists throughout the pandemic. Visitors must be fully vaccinated to enter and still must take a Covid-19 test and quarantine.
The other places moved up to Level 3 on Tuesday were:
-- Antigua and Barbuda (up from Level 2)
-- Benin (up from Level 1)
-- Ghana (up from Level 2)
-- Grenada (up from Level 1)
-- Turks and Caicos Islands (up from Level 2)
A view of an Amsterdam canal on August 19. The Netherlands got moved on Tuesday to the CDC's Level 3, an improvement over its previous Level 4 placement.
Oscar Gonzalez/NurPhoto/Getty Images
A move to Level 3 was actually good news and a sign of progress for the United Arab Emirates, which had been at Level 4. Other nations that moved from Level 4 to Level 3 were:
-- The Netherlands
Not vaccinated? Don't go
In its broader travel guidance, the CDC has recommended avoiding all international travel until you are fully vaccinated.
"Fully vaccinated travelers are less likely to get and spread Covid-19. However, international travel poses additional risks, and even fully vaccinated travelers might be at increased risk for getting and possibly spreading some Covid-19 variants," the agency said.