UDY WOODRUFF: As we have been
mentioning, the U.S. has passed
yet another tragic marker

in the pandemic.

More than 200,000
people have died in this
country from COVID-19 and
related complications.

That, in a period of less than
eight months, is nearly twice
as many Americans who have

been killed in every
major conflict since
the Korean War combined.

Our understanding of how
the coronavirus is spreading
continues to evolve. We want to

use this moment to
clarify much of the latest
scientific thinking.

First, a report from Stephanie
Sy, followed by a conversation
with William Brangham.

WOMAN: The coronavirus can
remain infectious on plastic and
steel surfaces for up to three

days.

WOMAN: That has many people
worried about shopping
and other everyday tasks.

MAN: Because you have got to
be putting that disinfectant
on these groceries.

STEPHANIE SY: This was the sound
of fear early in the pandemic,
after studies showed that

the novel coronavirus
could live on surfaces
for hours, even days.

It led to a furious wave
of scrubbing, disinfecting
and sold-out cleaning
supplies across the

country.

DR. EMANUEL GOLDMAN, Rutgers New
Jersey Medical School: But the
problem with those experiments

is that they didn't
relate to what a real-life
scenario would be like.

STEPHANIE SY: That's Dr. Emanuel
Goldman, a microbiologist at
Rutgers New Jersey Medical

School.

In July, he published this
article in the British medical
journal "The Lancet" arguing

that these early studies greatly
exaggerated the amount of
virus that could actually be

found on surfaces in the
real world. He pointed
out that the lowest amount
of infectious particles

researchers used to test
surfaces in the lab was
10,000, a huge amount.

DR. EMANUEL GOLDMAN: You would
need something like 100 people
coughing or sneezing on the

same small surface area to get
anywhere near the amount of
virus that they used in these

experiments.

STEPHANIE SY: He says these
mistakes, and a lack of
scrutiny, have siphoned limited

resources from everything from
subway systems to schools for
excessive deep cleaning that

shows little evidence of
helping prevent COVID spread.

DR. EMANUEL GOLDMAN: Our
mothers taught us, you go to the
bathroom, you wash your hands.

You prepare food, you wash
your hands. You touch something
dirty, you wash your hands.

That's all you have to do.

Normal, routine hygiene
is sufficient to protect
against this virus.

STEPHANIE SY: Meanwhile, he
adds, not enough money and
attention have been paid to what

we now know is the primary way
the virus travels: the air.

DR. EMANUEL GOLDMAN: A teacher
from a school system saying
they were going to shut down

the schools one day a week for
deep cleaning and disinfection.
Wouldn't it be better to

use it instead on ventilation
systems or hiring more teachers,
so you could have fewer students

per class?

DR. SHELLY MILLER, University
of Colorado Boulder: You
want to try to replicate the

outside, indoors, in your space.

STEPHANIE SY: Dr. Shelly
Miller is an environmental
engineer at the University
of Colorado Boulder.

For decades, she's studied
the way pollutants and
infectious diseases
spread in indoor spaces,

and over the summer helped her
own university prepare for when
students and faculty return

to campus.

DR. SHELLY MILLER: You
want to control the source
of the contaminants.
And, in this pandemic,

the sources are the
infectious people inside.
And so, to control the
release of virus, you

want to wear a mask, and
you also want to be outside
of their personal cloud.

But some of the virus
can potentially leak
into the environment,
and then you have to

clean the environment. And
the way to do that is the
filtration and ventilation.

STEPHANIE SY: The simplest
way to do that, she says,
open a door or window.

But in many parts of the country
where it's still too hot,
or becoming too cold, to do

that, Miller says there
are different ways to
increase a building's
mechanical ventilation

and filtration.

Here's a basic guide: Buildings
up to code should already
be replacing the inside air

with outside air three times
an hour. But with coronavirus,
that should be doubled,

to six exchanges per
hour, and, ideally, to
nine exchanges per hour.

And, crucially, the more
people there are contained in
a space, the more exchanges are

needed. HEPA filters, which
stands for high-efficiency
particulate air, should
also be added to ventilation

systems to increase protection.

If I walk into a restaurant
or a classroom, is there a way
for me to personally tell if

that is a safe place to be,
if there's enough ventilation?

DR. SHELLY MILLER:
Unfortunately, at this
point in time, no.
And that is why, a lot

of times, I have been saying,
well, we really need to address
this. We need to give buildings

and classrooms and other
facilities resources,
so they can -- so they
can let the public

know how they have
attended to this.

STEPHANIE SY: She and others
say the Centers for Disease
Control and Prevention and the

World Health Organization have
been too slow to move away
from early guidance on surface

disinfection, and towards
clearer guidance on preventing
airborne transmission.

Last Friday, the CDC did
add language on its Web
site about aerosols from
coughing or breathing

spreading the virus, and
the need for ventilation,
then suddenly removed it.

DR. SHELLY MILLER: So, the only
rule of thumb I can say is,
if you walk into a space and

it feels hot and stuffy in
there, and you can smell smoke
and you can smell different

odors, then it's
probably not ventilated
enough, and you probably
shouldn't spend very much

time in there.

STEPHANIE SY: Even portable
air cleaners can help, and Dr.
Miller and her colleagues have

created a guide for schools
on these, which you can
find on our Web site.

The bottom line: If you're
thinking about going back to
the gym, to a restaurant, your

office or school, keep
washing your hands, keep
wearing your mask, and
keep social distancing.

But don't let those deep
cleans fool you. Ask what
they have done about the air.

DR. EMANUEL GOLDMAN: The problem
is that it's been out there
for so long, and Shakespeare

said it the best, what's done
cannot be undone. And it's going
to be a long time to turn the

ship around, if ever, because
a lot of people still are
operating on these assumptions.

STEPHANIE SY: For the
"PBS NewsHour," I'm
Stephanie Sy in Phoenix.