The Centers for Disease Control and Prevention is expected to end the use of Title 42, a pandemic-era public health policy used by both the Trump and Biden administrations to rapidly expel migrants at the border, by late May, according to multiple reports.

Why it matters: U.S. officials have been bracing for the policy's end, which could fuel already rising numbers at the border. The government has readied a sweeping contingency plan, preparing for a worst-case scenario of up to 18,000 migrants being taken into custody each day, Homeland Security officials told reporters Tuesday.

What they're saying: The CDC cited the decreased risk that migrants would contract or spread COVID-19 in detention facilities, according to the Wall Street Journal. The delay in ending the policy until May 23 provided DHS more time to prepare.

• "We are finalizing our current assessment and will release more information later this week," CDC spokesperson Kristen Nordlund told Axios.

By the numbers: Border Patrol chief Raul Ortiz said Tuesday at a conference in San Antonio that they expect migrant apprehensions to reach 1 million in the coming days — just halfway through the fiscal year.

• Border resources are already stretched with significantly more people attempting to cross the border than normal, including from far-away countries that make deportation difficult.
• Encounters with migrants already are double the levels from this point last year, with more than 900,000 encounters, according to the DHS officials.

What we're watching: DHS is preparing for the possibility of three escalating scenarios once Title 42 is ended, the first of which reflects the current situation with border officials taking into custody an average of 7,000 migrants a day.

• The most extreme scenario would involve a massive 12,000–18,000 migrant encounters every day.
• Those would likely include some of the roughly 25,000 people in Mexican shelters DHS intelligence believes have been waiting to cross as soon as Title 42 is lifted, as Axios has reported.

The backstory: The CDC's Title 42 order was first issued under former President Donald Trump in March 2020, using the pandemic as a reason for turning back migrants attempting to enter the U.S. without the chance to seek asylum.

• Immigration advocates, progressives and Democratic congressional leaders have been pressuring Biden to end the use of the policy that turns back families and single adults at the border.
• The policy has been criticized for infringing on people's rights to seek asylum as well as for sending migrants to parts of Mexico or other countries where they have faced danger and violence.
• On the other end, Republicans as well as Democratic Reps. Henry Cuellar (Tex.) and Vicente Gonzalez (Tex.) this week called on DHS and Health and Human Services to keep the policy in place out of concern that DHS is unprepared to handle a potential rush of people to the border.

What's happening: DHS has enlisted help from FEMA and has already begun building additional temporary facilities at the border, seeking additional bus contracts to help transport migrants and deploying hundreds of border officials from elsewhere to the southwest border, according to DHS officials.

• They have also established a Southwest Border Coordination Center to help manage a whole-of-government response to any mass migration event.
• The administration also recently began offering the COVID-19 vaccine to migrants at the border.