(CNN) — The CDC added one new destination on Monday to its "high" risk list for Covid-19.
Azerbaijan, which borders the Caspian Sea between Iran and Russia, moved to Level 3, or "high" risk.
Locations at Level 3 now account for more than 125 of the roughly 235 places monitored by the US Centers for Disease Control and Prevention -- more than half of all listings.
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, just one destination was added to Level 3 on August 29:
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. The CDC advises against traveling to these destinations. Under the new system, no destinations have been placed at Level 4 so far.
The Caribbean island of Saba was moved to Level 2 on Monday.
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 two new Level 2 places on Monday:
The North African country of Morocco was previously listed at Level 3. The Caribbean island of Saba was previously at Level 1.
There are 20 places listed at Level 2 this week. Some of the more-visited places in this category are India, Kenya and South Africa.
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.
No new places were added to the category on August 29.
About 20 places were in the "low" risk category this week. A few of the more popular places with world travelers in the "low" risk category this week included Tanzania and Egypt.
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.
No new destinations were added this week
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 Hungary and Vietnam.
Nearly 70 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, 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. If you're concerned about a travel-specific health situation not related to Covid-19, check here.