For people planning a getaway to Mexico for the holidays, the Centers for Disease Control and Prevention (CDC) has stern advice: Don’t. The CDC on Saturday assigned its highest-level warning against travel to Mexico, which has surpassed one million coronavirus cases. “Travelers should avoid all travel to Mexico,” the United States’ top health protection agency said in a written statement declaring level 4, or the red warning. The warning comes just days before Thanksgiving, when thousands of travelers flock to Mexico’s tourist destinations. In the advisory, the CDC said that people could increase their chances of contracting and spreading COVID-19 by traveling there. The advisory also noted that if people become infected with COVID-19 while traveling abroad, they can be denied re-entry. “If you are exposed to someone with COVID-19 while traveling, you may be quarantined and will not be allowed to return to the United States until 14 days after your last known exposure,” according to the notice. The top three world destinations for American travelers this year are in Mexico: Cancun, San José del Cabo and Puerto Vallarta. “Mexico has been a leader in the recovery of tourism since COVID-19 began,” according to the Allianz insurance company. “The country’s accessibility and security protocols, such as restricted capacity at resorts to allow for adequate social distancing, may be helping drive demand, along with the promise of a warm-weather escape.” But in those three tourist destinations, there has been a high rate of COVID-19. In the municipality of Benito Juárez, Quintana Roo, where Cancún is located, 6,585 cases of COVID-19 have been registered. In the municipality of Los Cabos, in Baja California Sur, 4,233 cases have been confirmed. And in Puerto Vallarta, Jalisco, 2,507 cases have been registered. COVID-19 testing is not widespread in Mexico, which is why former health officials have said that the number of cases and deaths could be higher than reported. Although restrictions have been placed on crossing the US border with Mexico by land, the limits do not apply to travel by air.