Santiago Niltepec, Mexico – Carlos Perez, a 30-year-old Colombian migrant from Bogota, was on track to reach the United States border with his wife and 11-year-old son by the new year.

The trouble came, however, when his wife became overwhelmed with fatigue as they reached the city of Tapachula in southern Mexico. By that point, they had travelled 2,500km — more than 1,550 miles — on foot.

So, Perez bought a bicycle. Often, he pedalled while his wife and child sat on the handlebars. On treacherous roads and at night, Perez walked alongside them as they rode slowly through darkness.

But a road accident in mid-November tore the skin from his shins and bloodied his wife and son’s arms.

Speaking a day later from a temporary migrant camp in Santiago Niltepec, Perez expressed a fear that their injuries will cost them the chance to cross into the US before President-elect Donald Trump takes office on January 20, 2025.

“I don’t know if it’s possible to reach the border in time now,” Perez said.

Like many of his fellow migrants and asylum seekers, Perez fears that Trump will follow through on his pledges to “close” the US border with Mexico.

Trump, a Republican, has teased that his incoming administration plans to declare a national emergency and deploy military forces to prevent unauthorised crossings, which he likens to an “invasion”.

Already, Trump has claimed that early negotiations with Mexico to crack down on migrants and asylum seekers have borne fruit.

“Mexico will stop people from going to our Southern Border, effective immediately,” Trump wrote on social media on November 27. “THIS WILL GO A LONG WAY TOWARD STOPPING THE ILLEGAL INVASION OF THE USA.”

Still, it is unclear whether his hard-knuckle rhetoric will help stem the flow of people coming to the US — or fuel it in the lead-up to his inauguration.

As blood soaked into his fresh bandage, Perez indicated that he had not yet given up hope of reaching the border. His eyes flitted to the closed white curtains of a mobile clinic set up by Doctors Without Borders (MSF).

“My son is inside. They are cleaning and bandaging his body. We can only wait to see if we can heal in time to make it,” he said.

He told Al Jazeera that his family fled gang warfare and extortion in their home city. Others in the camp had escaped poverty, death threats and instability.

One man, Omar Ramirez, described fleeing political persecution under President Nicolas Maduro of Venezuela.

Ramirez, who is in his forties, was a well-respected digital journalist in the country. But at the camp, insects crawl in and out of the open sores on his feet.

Clutched closely to his chest is an A4 plastic folder containing scanned documents proving his address, university degree and Venezuelan bank accounts — paperwork he hopes to use to apply for asylum in the US.

Among the sheets are his press pass for the 2007 Copa America football tournament and a blown-up photo of him smiling broadly next to a 19-year-old Lionel Messi.

But in the months since Venezuela’s contested presidential election in July, Ramirez explained that he stopped feeling safe in his home country. Maduro has sought to stifle questions about his re-election by detaining journalists and activists, according to human rights monitors.

“I was an outspoken critic of Maduro,” Ramirez said. “And I supported those who opposed him.”

As a result, Ramirez explained, “his power has meant it is unsafe for me to live with my family there now”.

He added that Venezuela’s ongoing economic crisis had also made his life there untenable.

“The minimum monthly salary is $4. Journalists like me are lucky to earn $6. Doctors, who have studied all their lives, earn around $8.”

Ramirez has pinned his hopes for asylum on an appointment through the CBP One app, a free digital platform established under the first Trump administration in 2020.

Outgoing US President Joe Biden has since expanded the app’s use, making it a requirement for the majority of asylum applicants arriving at the US border.

But critics have noted that the app can be glitchy, and not all asylum seekers have access to the technology needed to use it.

Wait times for an appointment have been as long as four months, according to a report from the advocacy group Human Rights Watch.

That can leave some asylum seekers vulnerable to attack or exploitation, as they wait in Mexico’s border regions for their appointment to arrive.

However, as Trump prepares for his second term in the White House, asylum seekers fear that even access to CBP One may be restricted.

On September 15, during his campaign for re-election, Trump promised on social media that he would “terminate the Kamala phone app”, using the name of his rival in the race, Kamala Harris, to describe CBP One.

He also accused the app of being used for “smuggling illegals”, an allegation made without proof. CBP One is run through the US Customs and Border Protection agency in the federal government.

The focus on CBP One is expected to be part of a larger push by the Trump administration to restrict asylum access, a right protected under both international and US law.

For Ramirez, that means getting to the US border sooner rather than later is vital.

He left his family at home in Venezuela, fearing what would happen on his trek north. In 2023, the International Organization for Migration even named the path to the US-Mexico border the “deadliest land route for migrants worldwide”.

Ramirez said he would not have been able to live with himself if his “wife and children joined him on this terrible path”.

If he manages to successfully claim asylum, Ramirez said he hopes to earn enough money to bring them safely to the US in the next year.

Ricardo Santiago, who heads MSF’s operations in southern Mexico, anticipates more migrants and asylum seekers like Ramirez will race to reach the border over the next month, before Trump takes office.

That would mean a reversal of current trends. September saw a four-year low in apprehensions at the US border, according to government figures. Still, Santiago said he has observed the numbers of migrants climbing again.

“The caravans are becoming larger and larger,” Santiago told Al Jazeera. “If in September and October they were made up of a few hundred people, now they are made up of thousands.”

Hundreds have sought medical attention from his 16-person MSF team in Santiago Niltepec, as a “migrant caravan” passed through the city in November.

Perez and his family were part of the recent caravan, which Santiago estimated to comprise 2,000 people.

Caravans began forming in 2018 as hundreds of migrants and asylum seekers banded together for safety. The groups offered an alternative to the human traffickers who charged thousands of dollars for safe transit to the US border.

Members of November’s caravan estimated they walked between 30 and 40 kilometres per day — between 19 and 25 miles — often travelling by night to avoid scorching daytime temperatures.

Still, experts say the groups often disintegrate before reaching their destination. And the caravans, no matter their number, are still vulnerable to unscrupulous authorities and Mexican drug cartels that use violence to demand bribes and ransoms.

“There has been a notable increase in patients who have experienced violent attacks in November,” Santiago told Al Jazeera.

Sometimes, members of the caravan get into fights among themselves, he explained. But the principal danger comes from outside groups like the cartels.

Santiago said he has heard reports of “attacks against young people, boys, girls, women and men of all ages who are exposed to kidnappings, extortion and sexual violence”.

One migrant, Miguel, who asked to be referred to by a pseudonym, folded his fingers into an imitation gun as he described the extortion he and others face from the cartels.

“If they grab you, you gotta find the money, or it’s over,” said Miguel, pressing his fingers to the side of his head.

Several members of the caravan, including Miguel and Perez, told Al Jazeera that as many as 60 people had not arrived at the temporary camp in Santiago Niltepec after leaving with the group the night before.

Whether they had organised safe passage north by car, become victims of kidnapping or were unable to keep pace with the caravan is unknown.

Just one week earlier, local media had reported that the body of a 36-year-old Venezuelan man was found on the side of the Pan-American Highway, a major thoroughfare that runs north to the US.

He had been part of another migrant caravan but was hit at high speed by a car. The driver fled the scene.

At Santiago Niltepec, a group of Venezuelan migrants and asylum seekers prepared for the next leg of the journey, onward to the city of La Ventosa.

One offered an open smile and a grim statement. “Survival is a lottery,” he said. “It could be us next.”