On Nov. 1, the agency added Russia, Belgium and Burkina Faso to the highest tier of coronavirus levels listed.
The CDC also notes that, if people must travel to these countries, they should be fully vaccinated prior to departure and follow all recommendations or requirements, including wearing a facemask and staying socially distant.
"Fully vaccinated travelers are less likely to get and spread COVID-19," the agency warned. "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."
There are dozens of countries listed as "Very High" risk.
Russia, for instance, has the third-highest amount of COVID-19 cases over the past 28 days, according to Johns Hopkins Coronavirus Resource Center. The U.S. still has the most, as well as the most deaths from the disease.
All of this comes ahead of tougher U.S. restrictions on international travel that are set to take effect on Nov. 8.
In addition, all international travelers will need to be tested for the virus before boarding a plane to the U.S. and there will also be more stringent restrictions for American and foreign citizens who are not fully vaccinated.
Those who are vaccinated will still need to show proof of a negative COVID-19 test within three days of travel and the unvaccinated must take a test within one day of travel.
The Associated Press contributed to this report.