OPIOID abuse is a national emergency, and the president is expected to declare it so officially. That will help free up funds for agencies to treat the problem. As part of this effort, researchers will try to determine when the opioid epidemic will peak, and how many more people are likely to die before it fades. The answer to that second question can vary by half a million deaths over the next decade. The epidemic appears to be gathering pace. Of the 65,000 drug-overdose victims in the 12 months to March 2017, 80% died from opioids (coroners’ reports may undercount that figure). The death toll now exceeds the height of the AIDS epidemic in 1995. Donald Burke, dean of public health at the University of Pittsburgh, points out that the number of fatal drug overdoses has doubled every eight years for the past 37. Unabated, a continuation of that trend would see annual opioid deaths rising to 90,000 by the middle of the next decade.

That analysis may be too simplistic. Mr Burke’s forecast is “plausible if nothing changes”, but it is “insane if it actually happens”, according to Michael Barnett, a professor of health policy and management at Harvard University. A more nuanced model would try to capture the fact that the opioid epidemic is not a singular event but a set of intertwined ones taking place in different places. Mr Barnett forecasts that the epidemic will gather pace for some time yet, before stabilising at about 45,000 deaths per year by 2025.

There is good reason to be pessimistic as the epidemic enters a new and deadlier phase. While deaths from prescription opioids are reaching a plateau, deaths from fentanyl—an illegal drug with 50 times the potency of heroin—have risen 92% over the past year to 22,000 in March (see chart 1). Brandon Marshall, a professor of epidemiology at Brown University, worries that this rise demonstrates the difficulty of preventing addiction. Mr Marshall’s worst-case scenario forecasts that opioid deaths will rise to 100,000 a year by 2025. His middling scenario is still dire: it expects deaths to increase by half, to 52,000 by 2019, before falling slowly.

Epidemiologists are frantically scrambling to go beyond simple best-guess estimates to dynamic models that can forecast addiction and overdoses more accurately. The Centres for Disease Control and Prevention (CDC) hopes that in time it can develop an early warning system, using novel data inputs, that will be able to identify opioid outbreaks before they become deadly. The CDC disbursed some money to 20 states last month to improve their data collection on overdoses.