(CNN) — Island destinations from the Caribbean Sea to the Indian Ocean joined a handful of Eastern European countries among the latest places deemed "very high" risk for travel by the US Centers for Disease Control and Prevention.
Grenada, Saint Kitts and Nevis, Mauritius, Albania and Serbia on Monday moved to the "Level 4: Covid-19 Very High" category on the CDC's evolving list of travel notices.
Afghanistan, which has been in turmoil since the Taliban takeover and US withdrawal last month, also moved to Level 4, along with several more destinations.
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.
• Saint Kitts and Nevis
The CDC's travel notices range 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.
All of the destinations listed above moved up from "Level 3: Covid-19 High."
The Level 3 category applies to destinations that have had between 100 and 500 cases per 100,000 residents in the past 28 days.
Israel was also listed as a Level 4 update on Monday afternoon. However, Israel was already listed in the Level 4 category before the weekly update. The CDC has not immediately responded to CNN's request for clarification.
New 'Level 3' destinations
Four other destinations moved to the Level 3 category on Monday: Australia, Brazil, Ethiopia and Romania.
Brazil moved down from Level 4, while Australia, Ethiopia and Romania were previously listed in the Level 2 "moderate" category.
Australia has recently struggled to contain an outbreak of the highly contagious Delta variant, which has spread to the major population centers of Sydney, Melbourne and Canberra, leading to lengthy lockdowns.
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.