SOME 382,000 Americans have overdosed on opioids—a group of drugs that includes prescription painkillers, heroin and synthetics—since the year 2000. That is greater than the number of American combat deaths in the second world war and the Korean and Vietnam wars combined. Despite this epic toll, there are early signs that at least one battle may be ending.

The Centres for Disease Control and Prevention (CDC) provide the best data for tracking the opioid epidemic. Its latest data, which cover the 12 months to the end of October 2017, show that opioids were responsible for some 46,041 deaths (see chart) in that period. While provisional and subject to revision, that number was at least not dissimilar to the previous month’s figure of 46,202.

Two trends emerge from the numbers. The first gives cause for cheer: deaths from heroin and prescription opioids are falling. Combined, the two drugs were responsible for 29,600 deaths in the 12 months to October 2017, 4% below their peak in figures released five months earlier. The second trend provides less reason for optimism. Deaths from synthetic opioids such as fentanyl—a drug up to 50 times stronger than heroin—rose 12% between May and October last year, to 26,760. Assuming the two trends have continued, deaths from synthetic opioids probably surpassed those from heroin and prescription drugs in February this year.

The precise workings of the epidemic in recent months are not well understood, but a few elements stand out. The first is that deaths from prescription medication are likely to have been pushed down by lower availability of those drugs. Official data from the CDC show that prescription rates were nearly 20% lower in 2016 than at their 2012 peak. IQVIA, a health consultancy, reckons that prescriptions fell by another 10% in 2017. Donald Burke, dean of the University of Pittsburgh’s graduate school of public health, thinks there is “almost certainly cause and effect” between prescription rates and deaths.