Opioids could kill nearly half a million people across America over the next decade as the crisis of addiction and overdose accelerates.

Deaths from opioids have been rising sharply for years, and drug overdoses already kill more Americans under age 50 than anything else. STAT asked leading public health experts at 10 universities to forecast the arc of the epidemic over the next decade. The consensus: It will get worse before it gets better.

There are now nearly 100 deaths a day from opioids, a swath of destruction that runs from tony New England suburbs to the farm country of California, from the beach towns of Florida to the Appalachian foothills. In the worst case scenario put forth by STAT’s expert panel, that total could spike to 250 deaths a day, if potent synthetic opioids like fentanyl and carfentanil continue to spread rapidly and the waits for treatment continue to stretch weeks in hard-hit states like West Virginia and New Hampshire.

If that prediction proves accurate, the death toll over the next decade could top 650,000. The average toll across all 10 forecasts: nearly 500,000 deaths over the next decade.

The more middle-of-the-road forecasts suggest that by 2027, the annual US death toll from opioids alone will likely surpass the worst year of gun deaths on record, and may top the worst year of AIDS deaths at the peak of that epidemic in the 1990s, when nearly 50,000 people were dying each year. The deep cuts to Medicaid now being debated in Congress could add to the desperation by leaving millions of low-income adults without insurance, according to the nonpartisan Congressional Budget Office.

The overdoses will cause immeasurable pain to families. They will also cost the US economy hundreds of billions of dollars.

“It took us about 30 years to get into this mess,’’ Robert Valuck, professor at the University of Colorado-Denver’s School of Pharmacy and Pharmaceutical Sciences, told STAT. “I don’t think we’re going to get out of it in two or three.’’

It’s already so bad that once unthinkable scenes of public overdose are now common: People are dying on public buses and inside fast-food restaurants. They’re collapsing unconscious on street corners and in libraries after overdosing on prescription pain pills, heroin, and fentanyl. A customer in Anchorage, Alaska, hit the floor of a Subway while trying to order a sandwich. A mom in Lawrence, Mass., sprawled in the toy aisle of a Family Dollar as her little girl screamed at her to wake up. A grandmother in East Liverpool, Ohio, slumped in the front seat of an idling car, turning blue, while a toddler in dinosaur pajamas sat in the back.

There are so many deaths, some coroners are running out of room for bodies.

The most recent national statistics count more than 33,000 opioid-related deaths across the United States in 2015. Many victims are young, often in their 20s or 30s. Increasingly, many are white. But the plague touches all demographics: farmers and musicians, lawyers and construction workers, stay-at-home moms and the homeless.

Most of the forecasts produced by STAT predict the annual death toll will increase by at least 35 percent between 2015 and 2027. Under the gravest scenarios, it could triple — to more than 93,000 deaths a year.

On this, all the experts agree: Fatal overdoses will not even begin to level off until sometime after 2020, because it will take time to see whether the federal government’s efforts to boost drug enforcement and push doctors to write fewer prescriptions for opioid pain pills are effective.

The worst-case scenario is built around the assumption doctors will continue to freely prescribe and that people addicted to opioids will continue to be exposed, perhaps unknowingly, to powerful synthetic compounds like carfentanil, an elephant tranquilizer capable of killing a human with just a couple of grains.

The best-case projection has fatal overdoses falling below 22,000 a year by 2027. But experts say getting to that level would require a major public investment in evidence-based treatment options and a concerted push among medical providers to control pain with nonnarcotic therapies before trying prescription opioids. Right now the United States spends about $36 billion a year on addiction treatment — and just a fraction of those in need are getting care.

By contrast, federal officials estimate that opioid abuse drains nearly $80 billion a year from the American economy because of expenses tied to health care, criminal justice, and lost productivity.

In addition to the forecasts, provided by academics who specialize in epidemiology, clinical medicine, health economics, and pharmaceutical use, STAT conducted more than 40 interviews with politicians and patient advocates, providers and payers, doctors and drug makers. This analysis is also informed by a review of presentations from top Trump administration health officials.

President Trump, who has vowed to make opioids a priority, has appointed a commission led by New Jersey Governor Chris Christie to explore solutions, but it hasn’t yet laid out its ideas — and in the meantime, the administration’s proposed budget would slash most domestic spending, which health advocates call profoundly counterproductive.

“Are we doing enough of what we think works — prescription drug monitoring programs, medication-assisted treatment, naloxone?’’ said Dr. Donald Burke, dean of the University of Pittsburgh’s graduate school of public health.

“And,’’ Burke said, “are we matching the societal costs with a like expenditure in prevention?’’

The roots of the crisis stretch back generations to the 1980s, when pharmaceutical firms first marketed prescription opioids like oxycodone and hydrocodone to treat pain — and claimed they carried minimal risk for addiction.

Over the years these companies pushed hard to get pills in patients’ hands with strategies that included paying middlemen to circumvent state regulations and allegedly bribing doctors to prescribe opioids.

The results are staggering: Opioid prescriptions nearly tripled between 1991 and 2011.

It has been abundantly clear in recent years that such prescriptions can be dangerous. From 2005 to 2014, the rate of opioid-related emergency department visits nearly doubled, according to a new report from the Agency for Healthcare Research and Quality. Yet as recently as 2015, doctors prescribed prescription painkillers to more than a third of American adults, despite limited upside for many patients.

“It’s like cigarettes in the ’50s: We look back at the way people smoked and promoted cigarettes as laughably backwards — magazine ads with doctors saying, ‘Physicians prefer Camels,’ ’’ said Dr. Michael Barnett, assistant professor of health policy and management at Harvard University.

“We have the same thing now — Oxycontin ads in medical journals where doctors would say, ‘Opioids are good for treating pain. They don’t have addictive potential.’ ’’

The state of Ohio, among a handful of governments currently suing drug makers, alleges that a “well-funded marketing scheme’’ led to its residents receiving 3.8 billion opioid pills from 2011 to 2015, fueling “human tragedy of epic proportion.’’ Fatal drug overdoses in Ohio have soared by 642 percent since the turn of the millennium.

Another statistic: The number of privately insured patients diagnosed with opioid dependence increased nearly sixfold in just five years, according to data compiled by Amino, a health care data analytics company.

In 2012, only 241,000 such patients had an opioid dependency diagnosis. By 2016, that number was 1.4 million. And those numbers don’t even account for the hundreds of thousands more battling addictions while on Medicaid or Medicare, or while uninsured.

The surging death toll, affecting growing numbers of white Americans, sparked demand for action in ways unseen during past epidemics that disproportionately affected minority populations. Law enforcement officers started shutting down pain clinics, known as “pill mills,’’ where doctors accepted cash for painkiller prescriptions. But that only accelerated demand for heroin, as pill mill patients had trouble finding treatment to break free from their addictions.

Desperate to keep feeding their cravings and avoid the anguish of withdrawal, people from all walks of life — soccer moms in Vermont, C-suite execs in California, college-bound kids in West Virginia — began to shift from prescription pills to heroin, which was more potent and had become far cheaper, thanks to heightened drug trafficking into the United States by cartels. Two years ago, heroin deaths surpassed the toll from prescription opioids for the first time this millennium, according to The Washington Post.

Many of the experts STAT spoke with were even more concerned about the wave now crashing through communities: the synthetic opioids, such as fentanyl and carfentanil, that have flooded into the United States from China and Mexico. They can be cheaper and even deadlier than heroin — and can be made at home or ordered online. Between 2013 and 2015, deaths linked to these potent opioids tripled to more than 9,000.

The drugs can be so deadly, the US Drug Enforcement Agency this month urged first responders to carry naloxone in case they accidentally overdose while trying to help a victim — as has already happened to officers in Ohio and Maryland.

Because they’re so strong, synthetic opioids have spawned strings of mass overdoses in cities throughout the eastern half of the United States.

And the most potent synthetic opioids haven’t even penetrated all the markets in the country.

“We’ve not seen the worst yet,’’ said Tim Robinson, CEO of Addiction Recovery Care, a Louisa, Ky.-based company that runs several rehab programs. “As we transition from heroin toward fentanyl and carfentanil, when it hits the rural areas in Appalachia, we’re going to see a lot more devastation.’’

Already, a long trend of declining death rates for young adults has been reversed: Death rates for people ages 25 to 44 increased from 2010 to 2015 in nearly every racial and ethnic group, in large part because of drug and alcohol abuse, The Washington Post found.

The New York Times recently reached out to hundreds of state and county health officials to piece together an estimate of total drug overdose deaths last year. Its projection: More than 59,000 fatalities, most from opioids.

In an interview with STAT at a national drug abuse summit earlier this year, Dr. Patrice Harris, then chair of the American Medical Association, said one key to bringing down the death toll is to spread the word that addiction is a chronic medical condition, not a personal failing.

Another key: getting more people access to medications that can reduce cravings, such as buprenorphine, methadone, and naltrexone — and convincing both patients and providers that such treatments don’t simply amount to trading one addiction for another.

“Any physician in this country can prescribe oxycodone in high doses, but they can’t prescribe buprenorphine unless they have special training,’’ said medical epidemiologist Jay Unick of the University of Maryland Baltimore County. “You just don’t have easy access to buprenorphine. And that’s crazy in a world flooded with opioids.’’

The end result: waiting lists for treatment that can stretch for weeks or months.

In West Virginia, Marshall University student Taylor Wilson tried for 41 days to get treatment after nearly dying from an overdose. Her mother, Leigh Ann Wilson, finally got a call saying Taylor had cleared a buprenorphine waiting list. Her daughter had died four days earlier, from another overdose.

A landmark report last year from then-Surgeon General Vivek Murthy found only 10 percent of the estimated 2.2 million Americans with an opioid-use disorder have received addiction treatment.

“We know what works,’’ Murthy said this past April. “We’re just not doing enough of it.’’