(CNN) — Antigua and Barbuda in the Caribbean and Bermuda in the Atlantic were added on Monday to the "very high" risk category of the US Centers for Disease Control and Prevention's regularly updated list of travel advisories.
The South American country of Guyana was the other new entry in the "Level 4: Covid-19 Very High" category.
People should avoid traveling to locations designated with a "Level 4" notice, the CDC recommends. Anyone who must travel should be fully vaccinated first, the agency advises.
Nearly 90 destinations are now listed in the highest risk category. 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 three new destinations added to Level 4 on September 20 are:
• Antigua and Barbuda
They were all listed last week in the Level 3 category. The Level 3 category applies to destinations that have had between 100 and 500 cases per 100,000 residents in the past 28 days.
The CDC's travel notices range from Level 1 ("low") to Level 4 ("very high").
New 'Level 3' destinations
Seven destinations moved to the Level 3 category on Monday:
• New Caledonia
• São Tomé and Príncipe
In three of those locations -- Andorra, Colombia and Kuwait -- the Covid-19 situation has improved, with the CDC dropping them from Level 4 to Level 3.
Four of the destinations are now at increased risk: New Caledonia moved up from Level 1, while Bonaire, São Tomé and Príncipe and Ukraine were previously listed in the Level 2 risk category.
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.
The CDC is expected to issue a contact tracing order requiring airlines to collect information from US-bound travelers, the White House said in its announcement on Monday.
The CDC's travel risk notices don't include a risk rating for the United States.