>>DR. RAVEN BAXTER: Imagine a field of rabbits.
Rabbits as far as the eye can see.
Like hundreds of millions of rabbits.
In the early 20th century, there was just such a thing in Australia.
About 50 years after a few pairs were introduced, rabbits had infested the continent, destroying
crops and competing with native animals for resources.
To control this hopping population, ranchers purposely infected some with the myxoma virus.
An epidemic raced through the rabbits, killing 99.8% of infected populations.
But a few bunnies survived.
And started having baby bunnies.
The next time the virus came along, 90% of the rabbits died.
But again, a few bunnies made it through...
Until the virus came back.
But this time, about half of the rabbits survived.
At least for a while, the rabbits became more resistant with every cycle and the virus less destructive.
This was natural selection unfolding over a relatively short amount of time, and it’s
one way pandemics can end: a virus doesn’t go away, but comes to a balance with its hosts,
however uneasy (and occasionally still lethal) that might be.
But is that always how pandemics end?
Let’s rewind.
An epidemic is what happens when a disease flares up in one area of the world.
A pandemic is what happens when infection rates grow exponentially, in different countries
and groups of people.
For a pandemic to start in the first place, a certain percentage of people must be vulnerable
to infection and that infection has to spread easily.
No vulnerability, no spread…
no pandemic.
But let’s say we do have a deadly, transmissible, global virus—for a pandemic to end, a certain
percentage of people must be immune.
They can’t catch it and they can’t spread it, or if they do, the consequences aren’t fatal.
We saw that with the rabbits—over several generations, they achieved a level of resistance.
The virus became what we call ‘endemic’—always hovering in the background, but not acutely
devastating.
But rabbits are notoriously speedy breeders.
If we think of a similar process evolving over human generations, it could take something
like 100 to 150 years to reach that same balance point.
That’s a long time and a lot of lives lost along the way.
Another way to end a pandemic is containment.
Things like social distancing and mask wearing cut off paths for a virus to travel.
And when a virus causes severe symptoms quickly, we can sometimes stop its spread.
This happened with SARS-CoV-1, a coronavirus closely related to SARS-CoV-2, which causes
COVID-19.
Patients infected with SARS-CoV-1 weren’t contagious until after they showed symptoms,
so sick people could be identified and isolated.
Within nine months, no new cases were being reported.
But that’s a pretty rare set of circumstances.
Not, for example, what we’ve seen with COVID-19.
It’s less lethal than the disease caused by SARS-CoV-1 but can spread before we start
feeling sick.
It’s hard to contain and new enough that we don’t have immunity against it.
So, what do we do?
How does this end?
Think back to those rabbits.
They developed a balance with the myxoma virus, but at great cost to their numbers.
And the virus keeps evolving.
Here’s the good news—we have something the rabbits didn’t.
Vaccines.
Vaccines are incredible tools—shortcuts to immunity.
They’ve helped us eradicate smallpox and severely limit diseases like measles and polio.
With vaccines, we can see fewer cases, fewer people severely ill, and fewer deaths.
Hospitals won’t be so overwhelmed, and our frontline workers can breathe a little easier.
But not everyone’s going to get a shot.
Some people can’t for health reasons, some people don’t want to be vaccinated, and
some people don’t have access to vaccines.
So we need to provide information, answer questions, and get vaccines out to everyone
who wants them.
A single person can be immune, but immunity involves all of us.
To really stop a pandemic, we need as many people as possible to get vaccinated.