The U.S. Centers for Disease Control and Prevention (CDC) on Monday advised against travel to Canada because of a rising number of COVID-19 cases.
The CDC elevated its travel recommendation to "Level Four: Very High" for Canada, telling Americans they should avoid travel to its northern neighbour. The CDC currently lists about 80 destinations worldwide at Level Four. It also raised the island of Curaçao to Level Four on Monday.
The United States in November lifted restrictions at its land borders with Canada and Mexico for fully vaccinated foreign nationals, ending historic curbs on non-essential travellers in place since March 2020 to address the COVID-19 pandemic.
Canada remains one of the top foreign destinations for Americans.
The Canadian government did not immediately comment Monday.
Last month, Canada's government implored residents not to leave the country for non-essential travel.
Canada advised residents in March 2020 not to travel abroad for non-essential reasons like tourism. It withdrew the notice in October -- before the first Omicron cases were reported -- citing the success of vaccination campaigns.
The CDC on Monday also lowered travel recommendations from Level Four to "Level 3: High" to Armenia, Belarus, Lesotho and Zimbabwe. It also rate Singapore as "Level 3," after it previously was listed as unknown.