WASHINGTON (Reuters) – The U.S. Centers for Disease Control and Prevention (CDC) on Monday advised against travel to neighboring Canada because of a rising number of COVID-19 cases as the omicron variant spreads.

The CDC elevated its travel recommendation to “Level 4: Very High” for Canada, telling Americans they should avoid travel. The CDC, which lists about 80 destinations worldwide at Level 4, also raised the island of Curacao to Level 4.

In November, the United States lifted restrictions at its land borders with Canada and Mexico for fully vaccinated foreign nationals, ending historic curbs on nonessential travelers put in place in March 2020 to address the COVID-19 pandemic.

Canada remains a top foreign destination for Americans.

“We are aware of the latest CDC advice,” said a spokeswoman for Canadian Foreign Minister Melanie Joly, noting that last month, Ottawa had urged residents against nonessential travel.

Canada first issued the advisory in March 2020 but withdrew it last October — before the first omicron cases were reported — citing the success of vaccination campaigns.

This month, Canada broke its one-day record for the highest number of people hospitalized with COVID-19. Last Friday, officials said new daily cases had soared by 65% in the previous week, threatening health care systems.

The CDC on Monday also lowered travel recommendations from Level 4 to “Level 3: High” to Armenia, Belarus, Lesotho and Zimbabwe. It also rate Singapore as “Level 3,” after it previously was listed as unknown.

The CDC says Americans should be fully vaccinated before traveling to Level 3 destinations.

COVID-19 hospitalizations in the United States reached a record high of 132,646, according to a Reuters tally Monday, as the highly contagious omicron variant pushed cases past the record 132,051 set in January last year.