-As the world faced the initial wave of Coronavirus infections,
some hoped a change in weather would end the pandemic,
that the virus would be seasonal.
-There's a theory that in April, when it gets warm,
uh, historically, that has been able to kill the virus.
You know, in April, supposedly, it dies with the hotter weather.
And that's a beautiful day to look forward to.
And I think when we get into April and the warmer weather,
that has a very negative effect on -- on that.
-Seasonality is one of the ways
we understand how certain viruses run.
And all that really means
is that they might show seasonal patterns.
So, some viruses, like influenza, for example --
we're all familiar with seasonal influenza --
it tends to be worse in the fall and the winter
and into the cold months.
And it largely goes away in the summer.
-The seasonality of a disease can be driven
by several different factors.
-For respiratory viruses,
we know that things like humidity and temperature
can affect basically how droplets float around
in the air, how aerosols behave.
-But the impact that environmental factors
like humidity and temperature
have on the spread of Coronavirus
is miniscule compared
to how much human behavior drives transmission.
-Yes, we saw certain parts of the United States
and the globe --
we saw their cases plummet over the summer,
but that was really more likely due to the interventions
that have been targeting human behavior --
the reduction of mass gatherings,
the wearing of masks,
the physical distancing six feet apart.
-And even still, the summer saw an uptick of cases
in warm states like Texas and Florida,
further proving that human behavior
is the driving factor behind the spread of Coronavirus.
-Early in a pandemic, when there's very low immunity,
it kind of doesn't matter what the weather is
because any two people can probably transmit to each other
under the right circumstances, right?
If they're close enough, if they're touching,
if they're indoors.
So, most of the time, we don't see temperature
and seasonality sort of start to kick in
until there's enough immunity in a population.
-If the population's immunity becomes strong enough
and infection rates decrease,
the virus will likely stabilize and become endemic.
-Endemic, the way the different seasonal strains
of influenza virus are endemic.
They live with us. They're background.
They're here all the time.
And like seasonal influenza, it tends to appear
much more aggressively as the weather gets cold.
We think that will probably happen with this virus,
but it's going to take a certain level of immunity
in the population for those kind of seasonal patterns to appear.
-But experts warn we are still a long way from mass immunity.
And getting there by allowing the virus to spread freely with
no mitigation would be impractical, unethical,
and potentially deadly.
-And that immunity will come from a variety of ways.
Maybe it'll come from a vaccine.
Maybe it'll come over time, over years,
as our population just grows naturally more immune.
But when we get to that point, it certainly is possible that
we could see this Coronavirus show seasonal properties.
-Experts also say that those early assumptions
about warm weather
may have significantly derailed control of the outbreak.
-Early action when there is an epidemic happening
is really, really critical.
There's this kind of early window of opportunity in which
if you act aggressively, you actually do have the chance
to prevent this small kind of focal outbreak
from becoming a large epidemic within a country
or from becoming a globalized pandemic,
as we've seen with COVID-19.
-Looks like by April -- You know, in theory,
when it gets a little warmer, it miraculously goes away.
I hope that's true.
-These statements that politicians make that may seem
minor at the time -- "Oh, don't worry about it.
You know, the sunlight will take care of it.
Summer will take care of it,"
those can really impact people's perception of risk.
And they can impact people's behavior.
And human behavior is what's driving this outbreak.
Seasonality is not driving the outbreak.
Seasonality is not going to curb the outbreak.
This pandemic is entirely driven by human behavior,
and it can only be resolved through changes
in human behavior.