The president is scheduled to hold a photo opportunity for the completion of the 200th mile of new border wall in Yuma, Ariz. Dave Nash, a spokesperson for the city, told ABC News that cases in Arizona are "going up like a hockey stick," rising alongside cases in Yuma itself, though he said he felt the county was prepared for uptick.
An hour west, in rural town of El Centro, residents are seeing by far the worst rates of infection and death in California, according to public data. The surrounding county, in the desert region along the Mexico border, is one of the few California counties that remains under some level of lockdown.
And to the east of Yuma, the city of Nogales is seeing the highest infection rates in Arizona.
At the border, American local, state and hospital officials in Arizona and California told ABC News they were concerned about the possibility that the virus crisscrossing the national boundary could be in part to blame, with the high number of essential workers and travelers who are permitted daily through checkpoints in accordance with limited restrictions announced not long after the outbreak began. They believe the Mexican states that sit flush against the American Southwest are feeling a similar strain from the epidemic.
Nationwide the U.S. has reported much higher figures than its southern neighbor, some 2.3 million positive cases and more than 120,000 deaths, according to a count by Johns Hopkins University. The states bordering Mexico account for approximately 368,000 positive cases. Border communities in Arizona and California have seen a more concerning increase in cases recently, relative to those in Texas and New Mexico, though officials in those states also said they're concerned.
Cases and deaths reported by the Mexican government had shown a relatively slow growth in the first few weeks of the pandemic when officials started reporting numbers in mid-March. But in recent days, the figures have been increasing at a faster rate than ever, with the latest number of total cases surpassing 180,000 and deaths near 22,000, according to The New York Times. Government officials have acknowledged both figures are undercounts due to lack of testing and delayed results, according to an Associated Press report.
"Mexicali is overwhelmed," Dr. Adolphe Edward, CEO of El Centro Regional Medical Center told ABC News, referring to the Mexican border town immediately south of El Centro. "They're at their highest peak. They are really, really struggling to the point that we have been calling on [aid organizations] to go to work there to help them."
Infection rates are similarly high across the entire Mexican state of Baja California, which stretches west to Tijuana, according to the New York Times' data.
Last week, the U.S. government extended for another month the travel restrictions that ban non-essential travels of non-U.S. citizens from Mexico into the country. But those travel restrictions, in addition to essential workers, do not stop the heavy flow of routine cross-border travel for the more than 250,000 Americans who live in Baja, California, and thousands who travel south to shop and eat and visit relatives and then return home, said El Centro Mayor Efrain Silva.
"Our border is extremely important to us," Silva said. "We're bonded by not just proximity, but we're bonded by blood in many cases."
In Nogales, Ariz., Mayor Arturo Garino said thousands of trucks cross the border every day for essential businesses, and people are in line for hours everyday to walk across. He said the city is not tracking the role border transit is playing in spreading the coronavirus, but said he believes it must be contributing.
"If you stand on a line at the border to come across and you're standing there for two hours, three hours, probably you're not social distancing," Garino said.
Authorized border crossers are subject to the same customs inspection conducted at U.S. airports across the country. Under current federal guidelines, the checks include visual screenings for possible COVID-19 symptoms and additional tests by health screeners if necessary.
Garino said cases skyrocketed after a series of festivities that attract large numbers from both sides of the border -- Easter Sunday, followed by Fiesta de Mayo, Mother's Day and Memorial Day. The city has cancelled its very popular Fourth of July festival, where more than 10,000 people typically gather for a parade and music.
Imperial County in California and Santa Cruz County in Arizona have released figures showing only a small percentage of coronavirus infections could be conclusively traced to people who crossed the border. But local and state officials and health experts told ABC News they have strong suspicions the numbers are significant.
They said it has been difficult to assess infection rates on the Mexico side of the border because so few Mexican towns have access to testing and other resources.
Garino said that Nogales, with a population of 22,000, shows more positive cases than Nogales, Mexico, which has more than 500,000 residents – even though the two towns meet at the border.
"There's something wrong here," Garino said of the coronavirus count.
Local officials in Mexicali and Nogales, Mexico did not immediately respond to ABC News' request for comment late Monday. A spokesperson for U.S. Customs and Border Protection referred ABC News' questions to the Centers for Disease Control and Prevention, which did not immediately respond late Monday.
In the U.S., Edwards said the medical center in El Centro has in recent days been forced to transfer large numbers of patients to other facilities in the area because the virus has "stretched our resources." He said he has now begun hearing from other area hospitals that they, too, are increasingly worried about running out of intensive care beds.
Scripps Health CEO Chris Van Gorder said the company’s hospitals in San Diego County in California have taken in hundreds of patients from Imperial County, but recently had to freeze transfers because they were running out of space.
Van Gorder said he sent a letter to the Trump administration in late April asking for the federal government to conduct medical checks at the border, "temperature checks at the very least," and mandate quarantine for suspected positive individuals. He said he was concerned that inadequate medical resources in Baja California could pose a "very real threat” if there were efforts to re-start the economy that would bring more traffic north.
For local officials, the gravity of the outbreak has begun to set in. Early on, Garino had been among those officials who expressed reservations about imposing a lockdown or closing the border. Last week, he joined a growing number of Arizona mayors to require his residents to wear masks in public.
"My concern right now is the health and well-being of the citizens in Nogales, Arizona," Garino said. "So if the border is going to be closed for non-essentials until July 21, I think that's a good move because at least several hundred thousand people within that month will not be able to come across if they're not essential."
ABC News' Quinn Owen contributed to this report.