(CNN) — The CDC's weekly update of travel health advisories has some of the most encouraging news for tourists it's had in months.
The US Centers for Disease Control and Prevention did not add a single new destination on Monday to its highest-risk category for travel.
This hopeful respite comes after months and months of discouraging additions to its Level 4 category, in which destinations are considered "very high" risk for Covid-19.
Last summer when the Delta variant of the coronavirus was of paramount concern, the CDC added a whopping 16 nations to Level 4 in one week. Some of those August 2, 2021, additions included travel favorites Greece and Ireland.
The CDC places a destination at Level 4 risk when more than 500 cases per 100,000 residents are registered in the past 28 days.
In late February, the number of spots in Level 4 swelled to more than 140, illustrating the vast range and rapid spread of Omicron. Since that peak, the number of destinations in Level 4 has been declining again and many places are relaxing or dropping their international travel restrictions.
CDC: Avoid Level 4 destinations
Romantic Venice is still a top destination in Italy, but the country remains on the CDC's Level 4.
Marco Bertorello/AFP/Getty Images
Still, the broad picture remains a mixed bag.
Almost 115 destinations remained at Level 4 on March 28. That's still almost half of the nearly 240 places the CDC covers.
The CDC advises avoiding travel to Level 4 countries. CDC thresholds for travel health notices are based primarily on the number of Covid-19 cases in a destination.
The CDC does not include the United States in its list of advisories, but it was color-coded at Level 4 on March 28 on the agency's map of travel risk levels.
Tourist favorites stalled on Level 4 include Aruba, Brazil, Canada, Egypt, France, Greece, Italy, Peru and Spain. The United Kingdom has been there since July 2021.
In its broader travel guidance, the CDC has recommended avoiding all international travel until you are fully vaccinated.
Changes at Level 3
Peru, home to bucket-list site Machu Picchu, has moved down to Level 3.
PERCY HURTADO/AFP via Getty Images
The Level 3 "high" risk category -- which applies to destinations that have had between 100 and 500 cases per 100,000 residents in the past 28 days -- saw five additions on Monday. They were:
• Bosnia and Herzegovina
• Saint Pierre and Miquelon
All five of them had previously been on Level 4.
Levels 2, 1 and unknown
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. The six new entries to Level 2 on March 28 are:
• The Bahamas
• The Philippines
• Saint Kitts and Nevis
All six places had been at Level 3 last week.
To be in "Level 1: Covid-19 Low," a destination must have fewer than 50 new cases per 100,000 residents over the past 28 days. Four places moved to Level 1 on Monday:
Chad dropped all the way from Level 4. India, which was ravaged last year during the Delta surge, dropped from Level 3.
Guinea and Namibia have come down from Level 2.
Angkor Wat is a must-see destination in Cambodia, but the CDC warns the nation's Covid risk is unknown.
MLADEN ANTONOV/AFP/AFP/Getty Images
Finally, there are destinations for which the CDC has an "unknown" risk because of a lack of information. Usually, but not always, these are small, remote places or places with ongoing warfare or unrest. The CDC made no new additions to the category on Monday.
The Azores, Cambodia, Macau and Tanzania are among the more-visited locations currently listed in the unknown category. The CDC advises against travel to these places precisely because the risks are unknown.
A medical expert weighs in on risk levels
Transmission rates are "one guidepost" for travelers' personal risk calculations, according to CNN Medical Analyst Dr. Leana Wen.
"We are entering a phase in the pandemic where people need to make their own decisions based on their medical circumstances as well as their risk tolerance when it comes to contracting Covid-19," Wen said in mid-February.
"You should interpret Level 4 to mean this is a place with a lot of community transmission of Covid-19. So if you go, there is a higher chance that you could contract the coronavirus," said Wen, who is an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health.
Some people will decide the risk is too high for them, Wen said. "Other people will say, 'Because I am vaccinated and boosted, I am willing to take on that risk.'
"So this really needs to be a personal decision that people weigh understanding that right now the CDC is classifying the different levels based on community transmission rates, and basically only that," Wen said. "They're not taking into account individual circumstances."
More considerations for travel
There are other factors to weigh in addition to transmission rates, according to Wen.
"The transmission rates are one guidepost," Wen said. "Another is what precautions are required and followed in the place that you're going and then the third is what are you planning to do once you're there.
"Are you planning to visit a lot of attractions and go to indoor bars? That's very different from you're going somewhere where you're planning to lie on the beach all day and not interact with anyone else. That's very different. Those are very different levels of risk."
Vaccination is the most significant safety factor for travel since unvaccinated travelers are more likely to become ill and transmit Covid-19 to others, Wen said.
"People who are unvaccinated remain at high risk and really should not be traveling at this point," she said.
People should be wearing a high-quality mask -- N95, KN95 or KF94 -- anytime they're in crowded indoor settings with people of unknown vaccination status, she said.
And it's also important to consider what you would do if you end up testing positive away from home. Where will you stay and how easy will it be to get a test to return home?