The teenager who arrived at Jose de Jesus Lopez's drug rehab clinic in the industrial Mexican city of Monterrey in December had unusual symptoms.

The 17-year-old's family had taken the boy to hospital a few days earlier when he'd had trouble breathing and then passed out after supposedly consuming cocaine, the director said. Now he was sweaty and nauseous. He'd been vomiting and couldn't sleep.

"Something doesn't add up," thought Lopez, who is also the head of an addiction center network in Nuevo Leon state, where Monterrey is located.

The boy's symptoms looked more like opioid withdrawal, even though Monterrey lies hundreds of miles to the southeast of Mexico's few heroin and fentanyl hotspots in northwestern border cities like Tijuana and Nogales.

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Just in case, Lopez administered a urine test. It came back positive for fentanyl.

Although Mexico is a major trafficking hub for the highly potent synthetic opioid, it has so far avoided a consumption epidemic within its own borders.

Drug distribution

The fentanyl issue in Mexico continues to spread as the U.S. is on the brink of an epidemic.  (REUTERS/Jose Luis Gonzalez)

But interviews with over two dozen drug researchers and health officials, as well as data obtained by freedom of information requests, reveal that use of the drug is creeping further into Mexico, even though the scale of consumption is clouded by a lack of data and testing.

The fear among some researchers and officials is that use of fentanyl could follow the trajectory of methamphetamine over the past decade, six of the sources said. Meth started as a U.S.-bound product, but transformed into a domestic drug problem over the last decade.

Mexico's mental health and addiction commission (CONASAMA) has classified fentanyl as an "emerging drug" because of an uptick in users seeking treatment, even though opioid users make up less than 2% of the some 168,000 people who sought drug treatment in 2022, the most recent year for which data is available.

"Fentanyl is not a public health problem at this moment," said Evalinda Barron, the general director of CONASAMA. Still, she said, "it's a concern."

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Unlike in the United States, where potent synthetic opioids like fentanyl cause tens of thousands of deadly overdoses per year, Mexico officially logged less than two dozen opioid-related deaths in 2021, the latest year for which government data is available.

Mexico's health ministry has publicly acknowledged gaps in the data. The ministry did not respond to a request for more recent statistics. The president's office did not respond to questions for this story. The security ministry referred Reuters to public comments by minister Rosa Icela Rodriguez that Mexico was working with the United States and Canada to stop synthetic drug trafficking.

Mexico is far less predisposed than the United States to a fentanyl epidemic, some health officials and experts say, because it does not have the same history of prescription pain medication abuse and heroin consumption.

Still, officials are sounding the alarm, including through a public information campaign warning of the drug's risks across the radio, internet and in schools.

Mexican President Andres Manuel Lopez Obrador said in January that while fentanyl consumption was low, the country "has to be careful of it" and he was seeking more information about its use in different states.

In Nuevo Leon, the number of dead bodies that test positive for fentanyl has been rising, data from the attorney general's office shows.

In 2013, one corpse tested positive. In 2018, there were 47. By 2023, 180 bodies tested positive, about 4% of the thousands of autopsies the attorney general's office performed last year.

The traces in Nuevo Leon bodies do not mean fentanyl was the cause of death. Autopsies in the state are often carried out when the suspected cause of death was vehicular accidents or homicide. Some may have had legally-administered medical fentanyl in their systems.

Still, said Carlos Magis, a public health professor at the National Autonomous University of Mexico, the data points to "the reality of a growing epidemic."

"The increase is very serious," said Magis, whose research with colleagues, including tracking local media reports, estimates that hundreds of Mexicans may be dying from opioid overdoses annually.

LACK OF DATA

Data on fentanyl use in Mexico is far from comprehensive.

Forensic authorities in more than a third of states lack equipment to detect whether the drug is present in corpses, according to responses to freedom of information requests Reuters made to all 32 states.

Seventeen states said they had equipment to detect it in cadavers, ranging from rapid urine tests to advanced methods like liquid chromatography–mass spectrometry machines, which analyze chemicals in biological samples.

In 13 states, including populous Mexico City and the State of Mexico, state forensic services lacked capacity for specifically detecting fentanyl. One state said it was unable to find records of testing capacity. Another had not replied at the time of publication.

Barron, whose responsibilities also include mental health, said such testing was important but there were other, more pressing data gaps affecting her work, such as accurate tracking of suicide deaths.

"There's always a shortage of resources," she said.

Still, the lack of tests makes it hard to get a handle on the scope of fentanyl's reach in Mexico.

"We're undercounting, for sure, the number of people who are dying from overdoses," said Cecilia Farfan-Mendez, a Mexico security expert at the University of California San Diego.

Mexico's deputy health minister Hugo Lopez-Gatell, during a press conference in April, acknowledged possible underreporting in opioid-related deaths, while noting that the body count would still be lower than in the United States even if it were off by a factor of 100.

SUPPLY ROUTES

In Mexico, current fentanyl consumption is most prevalent along the U.S.-bound transportation routes, especially in the border regions.

That's because Mexican cartels often leave small amounts of drugs along the way in order to create local markets, cover operational costs, and pay salaries in kind, said Mexican security consultant David Saucedo, who works with state governments and companies on national security issues.

The border cities where the drugs enter the United States become the biggest markets. Shipments criminal groups aren't able to smuggle are instead sold on the Mexican side, said Josue Gonzalez, a former federal Mexican security official.

Indeed, nearly 60% of the 333 people shown by CONASAMA data to have sought treatment for fentanyl use in 2022 were in only four border municipalities - Tijuana and Mexicali in Baja California, and Nogales and San Luis Rio Colorado in Sonora - which all lie along the Pacific route, the most utilized path for fentanyl trafficking, according to U.S. seizure data.

But criminal groups have diversified and expanded their routes, moving smaller quantities of the drug through central and eastern Mexico, said Gonzalez.

"What criminals want is to have innovation, new routes, and the least risk possible," he said.

Shifting routes pave the way for consumption in new parts of the country, Saucedo said.

Authorities seized 150 kilograms of U.S.-bound fentanyl in Nuevo Leon over the last year and a half - an "unprecedented" amount for the state, its security secretary Gerardo Palacios told Reuters.

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Juan Roque, head of mental health and addiction for Nuevo Leon's health department, said the state has recorded just a handful of fentanyl consumption cases, and said the users picked up the habit elsewhere. He and Palacios said there was no evidence fentanyl is being mixed into other drugs, such as cocaine or meth, that circulate locally.

But, in the rehab clinic in Monterrey, that's what Lopez thinks happened to his teenage patient, who said he'd never consumed fentanyl intentionally, and whose urine also tested positive for methamphetamine.

"Many people could die if we don't pay attention to this," said Lopez, who now keeps fentanyl testing strips on his desk.

In Mexico's traditional opioid heartlands, fentanyl's rise has been well documented.

A 2020 study found 93% of 59 heroin samples collected in Tijuana were laced with the drug. More recently, 126 of nearly 900 bodies that came through the Tijuana morgue tested positive between March 2023 and December 2023.

In Mexicali, a neighboring border city with its own history of heroin use, the number rose to nearly a quarter of the 1,764 corpses tested since June 2022, state data shows.

Traces of fentanyl are appearing elsewhere in the country. A recently published paper based on testing at a 2022 music festival outside Mexico City found 2 of 4 cocaine samples and 14 of 22 MDMA samples were adulterated with the opioid.

Roque, at Nuevo Leon's health department, said the rise of methamphetamine in Mexico more than two decades after its use first surged in the United States made him worry the same would happen with the far more deadly synthetic opioid.

Nationwide, treatment for meth use has soared over the last ten years, from less than 10% of people seeking rehabilitation treatment in 2013, to nearly half in 2022, according to nationwide government data.

"More of it began to stay on this side of the border," Roque said of the meth wave.

"The same thing could happen to us with fentanyl."