there was then another week or so between the illness appearing and
death. Depending on whether we look at illnesses or deaths, we get
two slightly different impressions of the outbreak. If we focus on newly
ill Ebola cases, we’d say that the Yambuku outbreak peaked after six
weeks; based on deaths, we’d put the peak a week later.
1976 Ebola outbreak in Yambuku
Data: Camacho et al., 2014Both datasets are useful, but they’re not measuring quite the same
thing. The tally of new Ebola cases tells us what is happening to
susceptible people – specifically, how many are getting infected –
whereas the number of deaths shows what is happening to people
who already have the infection. After the first peak, the two curves go
in opposite directions for a week or so: cases fall while deaths are still
rising.
According to Pacula, drug epidemics can be divided into similar
stages. In the early stage of an outbreak, the number of users
increases, as new people are exposed to drugs. In the case of
opioids, exposure often starts with a prescription. It might be tempting
to simply blame patients for taking too much medication, or doctors
for overprescribing. But we must also consider the pharmaceutical
companies who market strong opioids directly to doctors. And