And communities from Appalachia to the Rocky Mountains and beyond are feeling its effects at all ages. In August, in the latest sign of the direness of the situation, President Trump said he would declare the opioid crisis a national emergency, a move that could allow cities and states to access federal disaster relief funds.
Eighty-seven children died of opioid intoxication in 2015, according to the Centers for Disease Control and Prevention, up from just 16 in 1999. By comparison, gunshot wounds kill four or five times as many children each year.
But at hospitals like Primary Children’s in Utah, drug overdoses now outstrip gun injuries among young people.
“There are no pill parties happening in preschools,” said Dr. Jennifer Plumb, the emergency doctor who recently treated four opioid-sick toddlers in a night. “These kids aren’t making a choice because they are trying to get high on a substance. It’s that the pills are everywhere.”
Unlike infants born with addiction, these children are coming across heroin and other drugs in the days and years after birth.
In Philadelphia this summer, a 9-month-old rolled onto a needle while in bed with her father. Kyleeh Isabella Mazaba, 20 months, died after drinking methadone left in a water bottle in the family van. James Lionel Vessell Jr., 2, swallowed oxycodone pills he found in a purse on his mother’s bed. And in early August, Kentucky officials treated an infant and three emergency responders believed to have been sickened by carfentanil-laced heroin that traveled through the air.
Often, emergency responders attempt to revive children with Narcan, an overdose reversal drug that works on small bodies as well as large ones.
Then come the questions for investigators. How did the substance get there? How did the child find it? Can this be stopped?
Sometimes officials charge caretakers with neglect or manslaughter. In one case this year, the authorities accused a couple of child endangerment after they admitted to rubbing Suboxone on their daughter’s gums, an attempt to hide the fact that she was born with an addiction.
But often the details go undiscovered, with witnesses too young to offer their own accounts.
Penny Mae Cormani was born Nov. 12, 2014, to Cassandra Leydsman and Casey Cormani, both mired in addiction. A year later, while the three of them were staying with another couple, Penny ingested enough heroin to kill a grown man.
Ms. Leydsman, the grandmother, said she believes Penny was scooting around on the floor during breakfast and found a bit of heroin, eating it like any child would. The official record is silent on exactly how the infant found the substance. But Penny’s parents pleaded guilty to third-degree felonies — Cassandra to child abuse homicide and Casey to attempted manslaughter — and went to prison.
Cassandra Leydsman is likely to serve 36 months.
Ms. Leydsman, 68, is a devout Mormon who raised five children with her husband, a retired pharmaceuticals manager. She traced her daughter’s addiction back more than a decade, to a car accident that prompted a doctor to prescribe OxyContin.
This led to a pill addiction that led to a heroin addiction that ultimately ended in Penny’s death. The family buried Penny in a baby cemetery south of Salt Lake City. Ms. Leydsman visits regularly, bringing with her holiday decorations, balloons and soft toys. In prison, Cassandra is receiving drug treatment.
“She knows she’s responsible,” Ms. Leydsman said of her daughter. “And it’s a terrible burden to go around knowing you’re responsible for the death of your child.”
In Utah, most opioid overdoses at the state’s only children’s hospital involve buprenorphine, oxycodone, methadone and hydrocodone, and Dr. Plumb attributes the problem to the state’s continued dependence on legal painkillers.
In a state of three million people, pharmacists fill some 7,200 opioid prescriptions a day, according to 2015 data. Curious toddlers, Dr. Plumb said, are finding mom’s Suboxone strip, grandpa’s OxyContin.
In Montgomery County, Ohio, which includes Dayton, the story is different.
Drug peddlers have flooded the community with fentanyl, a legal synthetic used for extreme pain, and powerful analogues like carfentanil, a substance 5,000 times stronger than heroin.
Inhaling, touching or ingesting a carfentanil dose smaller than a few grains of salt can be lethal. Dr. Kelly Liker, the medical director for child advocacy at Dayton Children’s Hospital, attributes a growing number of child overdoses to the rise of these substances.
In September of last year, Lee L. Hayes, 2, died in Montgomery County of fentanyl intoxication. In April, Nathan L. Wylie, 13, died of similar poisoning. And in May, Mari’onna Allen, 1, fatally overdosed in her grandmother’s home on Dayton’s East Fifth Street.
“It’s a disgrace that kids have to be subject to this,” said Mari’onna’s great-grandmother, who declined to give her name. “They’re innocent, they don’t have a clue, and they don’t know drugs from candy.”
Doris Burke and Alain Delaquérière contributed research.
A version of this article appears in print on September 21, 2017, on Page A15 of the New York edition with the headline: ‘Pills Are Everywhere’: Opioid Crisis and Its Youngest Victims