(CNN) — The US Centers for Disease Control and Prevention on Tuesday added three destinations in Europe — from its frigid northern climes to its sun-soaked south — to its highest-risk category for travel.

In its weekly update of Covid-19 travel advisories, the CDC advised against travel to the following countries and placed them in its “Level 4: Covid-19 Very High” category:

• Malta
• Moldova
• Sweden

The CDC places a destination at Level 4 when more than 500 cases per 100,000 residents are registered in the past 28 days.

The island nation of Malta, a Mediterranean favorite, was also at Level 3 last week.

Far off the radar of most tourists, the eastern European nation of Moldova had previously been in the “Unknown” category. The CDC places destinations in that category when it doesn’t have enough reliable data to make an assessment.

Europe’s continuing woes

In another troubling sign for Europe’s Covid-19 situation, the CDC moved no destinations on that continent to a lower level in the past week.

Other big travel names that remain lodged at the CDC’s Level 4 include:

• France
• Germany
• Greece
• Ireland
• Italy
• Netherlands
• Portugal
• Spain
• United Kingdom

In fact, the United Kingdom has been at Level 4 since July 19.

However, Europe isn’t the only continent with popular tourist destinations on Level 4. Among the other places also considered at “very high” risk for travel are:

• Belize
• Jordan
• Singapore
• South Africa
• Turkey

Level 3 additions

A general view of the Obelisco de Buenos Aires in Argentina’s largest city.

Ricardo Ceppi/Getty Images

The Level 3 category — which applies to destinations that have had between 100 and 500 cases per 100,000 residents in the past 28 days — saw two additions Tuesday:

• Argentina
• Brunei

Argentina, a South American travel favorite that took a very cautious approach about letting in foreign visitors for most of the pandemic, had previously been at Level 2.

The move was good news for the tiny Islamic sultanate of Brunei, which had been at Level 4.

Level 2, Level 1 and unknowns

Destinations carrying the “Level 2: Covid-19 Moderate” designation have seen 50 to 99 Covid-19 cases per 100,000 residents in the past 28 days. That level saw three additions Tuesday:

• Cuba
• Gabon
• Guatemala

Cuba, the largest island in the Caribbean, had been at Level 3. Gabon, on Africa’s Atlantic Coast along the equator, and Guatemala, in Central America. had also been at Level 3,

In the category of “Level 1: Covid-19 Low” destinations, fewer than 50 new cases per 100,000 residents have been logged over the past 28 days. It saw just one addition — the island nation of São Tomé and Príncipe off the coast from Gabon.

Finally, there are destinations, as cited above, for which the CDC has an “unknown” risk because of a lack of information. Usually, these are small, remote places. On Tuesday, the CDC added three places to this category:

• French Polynesia
• New Caledonia
• Suriname

The CDC cautions even fully vaccinated travelers about venturing to destinations with no reliable statistics about the current Covid-19 situation.

“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.

Another tumultuous week

All of these CDC level changes are happening against a swirl of pandemic news affecting travel worldwide: