Drug overdoses killed about 72,000 Americans last year, a record number that reflects a rise of around 10 percent, according to new preliminary estimates from the Centers for Disease Control. The death toll is higher than the peak yearly death totals from H.I.V., car crashes or gun deaths.

Analysts pointed to two major reasons for the increase: A growing number of Americans are using opioids, and drugs are becoming more deadly. It is the second factor that most likely explains the bulk of the increased number of overdoses last year.

The picture is not equally bleak everywhere. In parts of New England, where a more dangerous drug supply arrived early, the number of overdoses has begun to fall. That was the case in Massachusetts, Vermont and Rhode Island; each state has had major public health campaigns and has increased addiction treatment. Preliminary 2018 numbers from Massachusetts suggest that the death rate there may be continuing to fall.

But nationwide, the crisis worsened in the first year of the Trump presidency, a continuation of a long-term trend. During 2017, the president declared the opioid crisis a national public health emergency, and states began tapping a $1 billion grant program to help fight the problem.