Mexico continues to struggle with high fentanyl consumption as experts warn data is clouded by lack of testing

Mexico is a major trafficking hub for the opioid fentanyl, and experts weighed in on the growing concern for how it's growing into an epidemic in the United States.

"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.