(CNN) — The US Centers for Disease Control and Prevention added six destinations to its "high" risk category for travel on Monday.
Two Central American countries -- El Salvador and Honduras -- received a Level 3, "high" risk designation. Bangladesh, Bosnia and Herzegovina, Poland and Fiji were also added to Level 3.
Level 3 became the top rung in terms of risk level in April after the CDC overhauled its ratings system for assessing Covid-19 risk for travelers.
The designation applies to places that have had more than 100 cases per 100,000 residents in the past 28 days. Level 2 and Level 1 are considered "moderate" and "low" risk, respectively.
To recap, these six destinations received "high" risk designations on Monday:
• Bosnia and Herzegovina
• El Salvador
There were more than 120 destinations at Level 3 on July 25. Level 3 locations account for about half the roughly 235 places monitored by the CDC.
Level 4, previously the highest risk category, is now reserved only for special circumstances, such as extremely high case counts, emergence of a new variant of concern or health care infrastructure collapse. Under the new system, no destinations have been placed at Level 4 so far.
More on Level 3
Much of Europe has been stubbornly lodged at Level 3 for months with the summer travel season in full swing. As of July 25, the following popular European destinations were among those remaining at Level 3:
• The Netherlands
• United Kingdom
Those aren't the only high-profile spots that find themselves at Level 3. Numerous other destinations around the world are among those in the "high" risk category, including the following:
• Costa Rica
• South Korea
The CDC advises that you get up to date with your Covid-19 vaccines before traveling to a Level 3 destination. Being "up to date" means you have had not only the full initial vaccinations but any boosters for which you're eligible.
The Philippines, with Coron Island pictured, moved up to "moderate" risk on Monday.
Nguyen Duy Phuong/Adobe Stock
Destinations carrying the "Level 2: Covid-19 Moderate" designation reported 50 to 100 Covid-19 cases per 100,000 residents in the past 28 days. The CDC designated five new Level 2 places on Monday:
• Equatorial Guinea
The move was bad news for all five places, which moved up from Level 1. There are fewer than 20 places in the "moderate" risk category this week.
In its broader travel guidance, the CDC recommends being up to date with your vaccines before traveling internationally.
To be listed as "Level 1: Covid-19 Low," a destination must have had 49 or fewer new cases per 100,000 residents over the past 28 days. Two new places were added to the category on July 25: Angola and Comoros.
There are more than 30 places in the "low" risk category this week.
A few of the more popular places in the "low" risk category this week include Indonesia and Tanzania.
Finally, there are the destinations the CDC has deemed to be of "unknown" risk because of a lack of information. Usually, but not always, these are small, remote places or places with ongoing warfare or unrest. Two places were added this week: Dominica and Ethiopia.
The CDC advises against travel to these places precisely because the risks are unknown. Other destinations in this category that typically draw more tourist attention include French Polynesia, Hungary, Macau and the Maldives.
There are nearly 65 places listed as "unknown" this week.
A medical expert weighs in on risk levels
Transmission rates are just "one guidepost" for travelers' personal risk calculations, according to CNN Medical Analyst Dr. Leana Wen.
We've moved into "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," 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.
There are other factors to weigh in addition to transmission rates, according to Wen.
"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," she said.
"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.
And it's also important to consider what you would do if you end up testing positive away from home.
While US-bound travelers no longer have to present a negative Covid-19 test to get home from international destinations, the CDC still advises testing before boarding flights back to the States and not traveling if you are sick. "Of course, if people have symptoms or exposure while traveling, they need to get tested, and if they test positive, to follow CDC's isolation guidelines," Wen told CNN Travel recently. If you're concerned about a travel-specific health situation not related to Covid-19, check here.