Will there be another pandemic in your lifetime?
The Black Death.
The 1918 Flu Pandemic.
COVID-19.
We tend to think of these catastrophic,
world-changing pandemics
as very unlikely events.
But between 1980 and 2020,
at least three diseases emerged
that caused global pandemics.
COVID-19, yes, but also
the 2009 swine flu and HIV/AIDS.
Disease outbreaks are surprisingly common.
Over the past four centuries,
the longest stretch of time
without a documented outbreak
that killed at least 10,000 people
was just four years.
As bad as these smaller outbreaks are,
they’re far less deadly than
a COVID-19-level pandemic.
In fact, many people born after
the 1918 flu lived their entire lives
without experiencing
a similar world-changing pandemic.
What’s the probability that you do, too?
There are several ways
to answer this question.
You could look at history.
A team of scientists and engineers
who took this approach
catalogued all documented epidemics
and pandemics between 1600 and 1950.
They used that data to do two things.
First, to graph the likelihood
that an outbreak of any size
pops up somewhere in the world
over a set period of time.
And second, to estimate the likelihood
that that outbreak would get large enough
to kill a certain percentage
of the world's population.
This graph shows that while huge
pandemics are unlikely,
they're not that unlikely.
The team used these two distributions
to estimate that the risk
of a COVID-19-level pandemic
is about 0.5% per year,
and could be as high as 1.4%
if new diseases emerge
more frequently in the future.
And we’ll come back to those numbers,
but first, let’s look at another way
to estimate the likelihood
of a future pandemic:
modeling one from the ground up.
For most pandemics to happen, a pathogen,
which is a microbe that can cause disease,
has to spill over from its normal host by
making contact with and infecting a human.
Then, the pathogen has to spread widely,
crossing international boundaries
and infecting lots of people.
Many variables determine whether a given
spillover event becomes a pandemic.
For example, the type of pathogen,
how often humans come into close contact
with its animal reservoir,
existing immunity, and so on.
Viruses are prime candidates
to cause the next big pandemic.
Scientists estimate that there are about
1.7 million as-yet-undiscovered viruses
that currently infect mammals and birds,
and that roughly 40% of these have the
potential to spill over and infect humans.
A team of scientists built a model
using this information,
as well as data about the global
population, air travel networks,
how people move around in communities,
country preparedness levels,
and how people might respond to pandemics.
The model generated hundreds of thousands
of virtual pandemics.
The scientists then used
this catalog to estimate
that the probability of another
COVID-19-level pandemic
is 2.5 to 3.3% per year.
To get a sense of how these risks
play out over a lifetime,
let’s pick a value roughly in the middle
of all these estimates: 2%.
Now let’s build what’s called
a probability tree diagram
to model all possible scenarios.
The first branch of the tree
represents the first year:
there’s a 2% probability of experiencing
a COVID-19-level pandemic,
which means there’s a 98% probability
of not experiencing one.
Second branch, same thing,
Third branch, same.
And so on, 72 more times.
There is only one path that results
in a fully pandemic-free lifetime:
98%, or 0.98,
multiplied by itself 75 times,
which comes out to roughly 22%.
So the likelihood of living through
at least one more COVID 19-level-pandemic
in the next 75 years
is 100 minus 22%, or 78%.
78%!
If we use the most optimistic
yearly estimate— 0.5%—
the lifetime probability drops to 31%.
If we use the most pessimistic one,
it jumps to 92%.
Even 31% is too high to ignore;
even if we get lucky,
future generations might not.
Also, pandemics are usually
random, independent events:
so even if the yearly probability
of a COVID-19-level pandemic is 1%,
we could absolutely get another
one in ten years.
The good news is we now have tools
that make pandemics less destructive.
Scientists estimated that early warning
systems, contact tracing,
social distancing,
and other public health measures
saved over a million lives
in just the first six months
of the COVID-19 pandemic in the US,
not to mention the millions
of lives saved by vaccines.
One day, another pandemic
will sweep the globe.
But we can work to make that day
less likely to be tomorrow.
We can reduce the risk
of spillover events,
and we can contain spillovers
that do happen
so they don’t become full-blown pandemics.
Imagine how the future might
look if we interacted
with the animal world more carefully,
and if we had well-funded, open-access
global disease monitoring programs,
AI-powered contact tracing
and isolation measures,
universal vaccines,
next-generation antiviral drugs,
and other tech we haven't even thought of.
It’s in our power to change
these probabilities.
So, we have a choice: we could do nothing
and hope we get lucky.
Or we could take the threat
seriously enough
that it becomes a self-defeating prophecy.
Which future would you rather live in?
