Heroin use in the US has grown by a staggering amount in recent years.

A report issued this summer by the Centers for Disease Control found the number of heroin users in the US had grown by almost 300,000 over the last decade, and the increase has occurred among men and women in almost every age group and at all income levels.

The spike has primarily been driven by the growing use of (and subsequent crackdown on the abuse of) opiate painkillers like Vicodin as well as heroin's increased availability as a cheap alternative to over-the-counter drugs.

The 2015 National Drug Threat Assessment, issued by the DEA in October, reveals not only how widespread heroin has become, but also where it is produced and how it enters the US.

The DEA report also found that, according to data from law-enforcement agencies, heroin availability was higher in 2015 than it was in 2008 in every region of the country.

Heroin availability increased in every region of the US between 2008 and 2015, according to the DEA. DEA 2015 National Drug Threat Assessment

“Most of the heroin available in the United States comes from Mexico and Colombia,” the DEA notes in its report.

“Despite significant decreases in Colombian heroin production between 2001 and 2009,” the report adds, “South American heroin continues to be the predominant type available in eastern US markets.”

Mexico and Colombia dominate the use market for the drug due to “their proximity, established transportation and distribution infrastructure, and ability to satisfy US heroin demand.”

Mexican cartels, however, have grown their share of the heroin market tremendously in recent years. Together, Mexican drug traffickers smuggled nearly a quarter-million pounds of heroin into the US in 2014, according to The Washington Post.

South America and Mexico are responsible for the vast majority of heroin found in the US in recent years. DEA 2015 National Drug Threat Assessment

The report finds that white-powder heroin made from Mexican poppies, but produced using South American methods, has been seized near the southwest American border and along trafficking routes that Mexican cartels have established over the last 20 years.

(Mexican black-tar heroin, historically found west of the Mississippi River, has also started appearing in the eastern US.)

Increased smuggling has been met with more vigilant law-enforcement efforts, and seizures along the border have jumped, from 1,016 kilograms (2,240 pounds) in 2010 to 2,188 kilograms (4,824 pounds) in 2014. Heroin is also seized at airports in Miami, Newark, New York City, and Orlando on a regular basis.

Heroin trafficking has increased along much of the US southwest border. DEA 2015 National Drug Threat Assessment

This production, the DEA notes, likely indicates that not only are Mexican drug organizations breaking free from a reliance on South American production, but also that they are aiming to take more extensive control over the US market for heroin.

In addition to increasing their heroin sales, this would allow Mexican organizations to diversify the kind of drugs they push to include cocaine, meth, and marijuana in addition to heroin.

Indeed, Mexican organizations have made a dramatic shift toward opium-poppy cultivation, reaching 17,000 hectares (42,008 acres) in 2014, an amount the DEA says could produce 42 metric tons (46.3 tons) of heroin. Colombia, in contrast, only had 800 hectares (1,977 acres) of opium-poppy cultivation that year, which the DEA says could produce just 2 metric tons (2.2 tons) of heroin.

Much of the opium cultivation in Mexico takes place on the mountainous west coast. This area is dominated by the immensely powerful Sinaloa cartel, as well as the ascendant Jalisco New Generation cartel. (The two organizations are suspected of cooperating to some extent.)

A soldier cuts open an opium poppy capsule at a poppy field, during eradication supervised by the Mexican Army on the outskirts of Morelia, Mexico, Thursday, March 4, 2010. AP

The Sinaloa cartel, regarded as the most powerful drug-trafficking cartel in the Western Hemisphere and in the world, already provided “80% of the heroin, cocaine, marijuana and methamphetamine — with a street value of $3 billion — that floods the Chicago region each year," in 2013, the DEA said at the time.

Heroin use in the US is more common in the Northeast and Midwest regions, and Mexican cartels are, according to the DEA, trying to expand their share of sales in those areas.

“Mexican organizations are now the most prominent wholesale-level heroin traffickers in the DEA Chicago, New Jersey, Philadelphia, and Washington, DC FD AOR [field division area of responsibility], and have greatly expanded their presence in the New York City area.

A map of cartel influence in the US. Sinaloa areas are shaded in orange, with darker shading indicating higher population density. DEA Strategic Intelligence Section

The outlook for heroin use in the US is grim. The criminal organizations that produce and transport it are making concerted efforts to increase their offerings, and the low cost and high demand ensure that America’s latest poison of choice will remain in high supply.

According to government data, drug-poisoning deaths involving heroin increased 244% between 2007 and 2013, a surge likely to continue unabated.

“Heroin use and overdose deaths are likely to continue to increase in the near term,” the DEA concludes.