64 ISE Magazine | www.iise.org/ISEmagazine
with Michael L. Washington
Michael L. Washington, Ph.D., is an industrial
engineer and health scientist working with the
U.S. Centers for Disease Control and Prevention’s
Center for Emerging and Zoonotic Infectious
Diseases. He also works with the Bloomberg
Philanthropies Data to Policy Initiative through
the CDC Center for Global Health/Division of
Global Health Protection providing assistance
in developing countries. He and his team
have created two spreadsheet models, one
to help healthcare facilities plan for a surge
in COVID-19 cases during the pandemic and
another that illustrates the resources needed
to conduct contact tracing and monitoring of
COVID-19 cases and its potential impact. Both
can be downloaded at no cost at www.cdc.gov/
coronavirus. His full interview can be heard on
Problem Solved: The IISE Podcast at podcast.iise.
org. He is an IISE member.
What is the general idea behind creating such models?
Models are an approximation of reality. There are people who think that models
are going to give you an exact answer. Models are just a simplified version of re-
ality and a tool to help manage possible future outcomes. It’s not going to tell you
exactly what you should do or exactly what should happen. That rarely occurs.
It’s just a tool to help you prepare for what could happen, what could not happen.
One of the main problems that’s happening now, especially with COVID, is
when people are saying “these models are way off” or “they’re incorrect.” The
fact that this is a new virus; we’re still learning about it and were including as
much as we can in our models that are in dealing with COVID to get as close
to reality as possible. But theres still a lot of stuff that we dont know, and that
makes it very difficult to model. We just need to help people, especially decision-
makers, understand that and give a range of outcomes that could occur based
upon the models, and that should help them make more informed decisions.
What factors can affect the range of possible outcomes?
There are a lot of things that can occur that will give you a wide range. One of
them is the uncertainty and the variables that we have. And so if youre using
a more statistical or mechanicalistic model in which the variables change or are
randomly selected, then you will get a range of certain outcomes.
One of the assumptions people are making now is that people are going to
obey wearing masks and staying at home, those types of things, and a lot of
models assume that. We cant model what people are actually going to do, and
of course, the model is going to be wrong because of that assumption. ... With
humans, things may change if 10% of the population stays home, if 30% or
100% – theres a wide range of possibilities. If the model is set on 30%, then the
population does something else, then yes, the model is going to be incorrect. If
we change the assumptions to what people actually did, chances are the model
is going to be correct.
What is the purpose of the COVID Surge model?
The main reason our team developed this model is that hospitals would run out of
resources if the outbreak became too bad. So we created a model that looks at the
number of ICU beds that are available. And a lot people are very concerned about
ventilators, so we included that in the model. We created a mechanicalistic model,
SEIR, (susceptible, exposed, infectious, recovered) and we used that model to
estimate the number of COVID cases that would occur, how many would need
hospitalization, how many would need to go into the ICU, how many would
need a ventilator. Then we matched that with the people using the model and
what resources they have. That could be the resources in a hospital, in a region
or even in a country. The model tells you when you are going to run out of re-
sources, how long youre going to run out of resources and eventually when youre
going to go back down to a level where you can manage the surge of patients.
Can this model be used by officials in various locations?
Thats what the model is designed to do – it is designed to look at your specic
situation, both from the disease’s perspective and also your resources. One of the
great things is we work for the CDC, and if there’s anybody that knows about
COVID or any outbreak of diseases, it’s the CDC. We consult them on the type
of parameters we should use. We can also send people out into the field to hospi-
tals. We can gather information for the model from our colleagues and it makes
it more usable almost immediately. ... The model is pretty robust to handle a
October 2020 | ISE Magazine 65
lot of situations, including new information and changes that
We have had people provide us feedback in ways to improve
the model, and that’s been very helpful. We’ve also heard from
people who contacted us to learn a little more about the model
as far as the details of how it works. And we’ve gotten feedback
from people within the CDC who said this is a great tool, they
appreciate it and they’ve been using it.
How does the COVID Tracer model work?
We thought there was a need to create a model to estimate how
much staff would be needed to do appropriate contact tracing –
how many hours it would take and what impact would it have
on the outbreak. It’s very similar to the COVID Surge model
in that it uses an SEIR model and we have a number of differ-
ent inputs that go into the model. One of the more interesting
things we added is that we keep track of patients who are in
certain stages, such as if they have just gotten sick, if they are
pre-symptomatic but shedding, if they are symptomatic and
shedding and if they recover. That’s important with contact
tracing because you want to find people as fast as possible and
isolate them, preferably before they start shedding. And the fact
that there are a number of people who are shedding and are as-
ymptomatic makes it very important to find those people early
and isolate them.
With Ebola, you really dont start infecting people until you
start showing symptoms. That was one of the things that people
thought about COVID in the very beginning was that we didnt
think people could transmit without showing symptoms. What
we did find out was people who are asymptomatic can transmit.
And so it makes it very difficult for the contact tracers to actually
appropriately isolate people who are sick but not showing any
symptoms. ... It’s all about making sure you have enough staff to
actually do contact tracing appropriately.
What are the strategies included in the model?
Those are complex strategies that we researched and found that
people have been using around the world. You can use those
in your situation if you think that strategy matches up to what
youre doing. ... That’s one of the things we try to emphasize
with the model – we have to tailor it to your situation. This
is also something I teach in my job working with Bloomberg
Philanthropies where we teach people in lower and middle-
income countries that we have models you are able to use. But
just because a situation works in New York doesnt mean it’s
going to work in a rural village in Zambia. You have to modify
the model to match your situation. Thats even true within the
United States, from state to state. Gainesville, Florida, is prob-
ably going to be very different from Los Angeles. You have to
modify the data that’s going in to match your situation in order
for the model to work appropriately.
With the first one, it’s more finding those who are symp-
tomatic and isolating them. That may not work as well because
by the time they are symptomatic, they have already been out
in the wild transmitting. In the second situation, you are again
focusing on those who are symptomatic and their contacts, and
youre asking the contact as soon as they show symptoms to iso-
late yourself, contact the people in the public health department
so they can start tracking you. Again, that is a slight problem in
that by the time they show symptoms, there are some who are
asymptomatic and they’re already spreading.
With the third situation, it is again isolating those that you
nd who are sick but then also isolating the contacts. You also
tell them to stay at home, because by the time they show symp-
toms, they’re already at home and they’re not spreading. You
contact the health department and they can start monitoring
you. Now as you can see, with each of those different strategies,
more and more resources are going to be required. So the tool
takes all of that into consideration. But it also shows the impact
of isolating people quickly.
As I said before, these are humans, and it’s very difcult to
predict what humans are going to do. And so we add a variable
in there such as compliance, how many people are actually go-
ing to comply, with staying at home or staying in contact with
the contact tracer. And the less people who are compliant, the
less likely the strategy is going to work.
The COVID models were based on previous
efforts with Ebola. Describe that project.
Back in 2014, when the Ebola outbreak was occurring, we de-
cided to create a tool to help decision-makers make decisions,
and that’s basically what all of these models are. We created the
model called Ebola Response and we took whatever informa-
tion that we could about Ebola, and at that time it was very lim-
ited. When you have something like Ebola where thousands of
people are dying every day, you have to make decisions quickly.
With the Ebola model, we were able to use that to push inter-
national agencies into contributing to all the efforts in western
Africa to help stop the outbreak.
Describe your work with Bloomberg Philan-
thropies to help people in other countries.
It’s been one of my passions since 2002 when I took my interna-
tional trip to Ghana to help with polio eradication. I went there
to teach the people on the ground about surveillance, about
checking data to appropriately identify if there are polio cases in
certain regions. I taught them how to use geographic informa-
tion software to help map out where all these different outbreaks
are occurring. ...
That international bug, and work, has really bitten me. In the
last couple of years working with Bloomberg Philanthropies,
I’ve accumulated a lot of miles. I work in a lot of different coun-
tries, and I get a lot of joy from that.
– Interview by Michael Hughes, IISE