Armenia, Cuba, Israel, Japan, Libya, Oman and the Democratic Republic of the Congo are all deemed "Level 4."
"Do not travel internationally until you are vaccinated and up to date with your COVID-19 vaccines," the agency said. "Getting vaccinated is still the best way to protect yourself from severe disease and slow the spread of COVID-19. In addition to following the requirements for international travel, CDC recommends that all travelers be up to date with COVID-19 vaccines before traveling."
Those who are not up to date with vaccines should follow recommendations for all travelers as well as additional recommendations.
The CDC says these travelers should get tested with a viral test no more than three days before the trip and self-quarantine for a full five days after travel.
All travelers are instructed to follow airline requirements as well as any requirements at the destination, including wearing a face mask, social distancing, proof of vaccination, testing or quarantine.
According to the agency, a country or territory is reported as Level 4 when there are more than 500 new coronavirus cases over the past 28 days per 100,000 population.
Anguilla, Brazil, Chile, Ecuador, French Guiana, Kosovo, Mexico, Moldova, Paraguay, Saint Vincent and the Grenadines, Singapore and the Philippines were also upgraded to Level 4 at the end of last month.
The "Level 3" COVID-19 travel health notice level is when there are 100-500 new coronavirus cases over the past 28 days per 100,000 population.
The CDC added Bangladesh, Montserrat and South Africa to that list on Monday.