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Below is the full-length interview with Dr. Rosalind Stanwell-Smith, filmed at the London School of Hygiene and Tropical Medicine External link. Dr. Stanwell-Smith discusses her role with the John Snow Society and the impact of John Snow's "original mind" on the science of epidemiology.
[MUSIC PLAYING]
ALYSSA GOODMAN: So my first question is, can you
tell us a little bit about your background
and how the John Snow Society started?
Because that wasn't on my list, so go ahead.
ROSALIND STANWELL-SMITH: Well my background,
I'm a medical epidemiologist.
I started off in surgery, but I felt the call of epidemiology.
And during the early '90s I had to run a course teaching people epidemiology.
And we went down to the John Snow Pub, just to give them
a kind of interesting thing.
And we found that the pub was really run down,
and no one was bothering about it.
And we knew there was this big heritage in the states,
so we were a bit embarrassed.
Especially because we had two guys from CDC who were lecturing on our course.
And so we said, well we must have a John Snow Society.
And that's how it started.
ALYSSA: What year was that, roughly?
ROSALIND: About 1990.
ALYSSA: OK, yeah.
ROSALIND: It took us a couple of years to drum up all the enthusiasm
and to get people involved.
And right from the start, it was meant to be
a network of not just epidemiologists.
We got people who worked in public health, people
who worked in microbiology, in statistics, in water, of course,
and in anesthesia.
ALYSSA: Right.
ROSALIND: I mean, let's not forget that he was basically an anesthetist.
And so it started off as a fun thing, but with a kind of serious intent.
That we shouldn't forget the memory of such an important man.
And the idea that there's all those different kinds of people involved
is interesting, because one of the things
that I find interesting about epidemiology,
especially the way that John Snow did it,
is that there were all these aspects to it way beyond just data collection.
But a sort of like, how do you know what's
normally happening in the neighborhood?
What are the politics of the water companies?
You know, kinds of statistics that apply and don't apply.
And so you have people from all of those walks of life now.
There's been a lot of criticism in a way,
of the way John Snow and some of the others of his time
have become an icon of epidemiology.
ALYSSA: Yeah, yeah.
ROSALIND: And people have said, well why him?
I mean he wasn't the only one doing maps.
He wasn't the only one who's beginning to look at statistics.
But what was very interesting about John Snow, I think the deductive reasoning.
The fact that yes, he was a qualified doctor,
but he was very much a scientist a doctor.
And he believed in measurement, and he was against the flow of the times.
There were other people who thought that cholera might be water borne,
but it was only as part of a general theory.
People sometimes want to know when did epidemiology start?
We didn't really call it epidemiology until well later in the century.
It's really a 20th century phenomenon, as such.
They wouldn't have thought of it like that at all.
They understood epidemics, because they had the word in French.
But it could be just one or two cases.
Maybe even one cases and it was an oddity disease.
And the idea of researching those epidemics,
they would have called like a study, or Snow often
referred to the great experiment that needed to be
done to show that water was the cause.
ALYSSA: And he had two famous studies, that I know about anyway.
One where he has the big map, not the cholera
map that we're talking about today, but the map of different water companies,
and which ones supplied parts of London.
And sometimes I hear the great experiment applied to that,
and sometimes I hear it applied to this.
To the actual cholera outbreaks.
Did he mean both, one, the other?
ROSALIND: I think when he referred to the great experiment,
he meant that the demonstration that water was conveying cholera.
He thought that he'd done enough, in his 1849 pamphlet, which
was just a short few pages.
But it wasn't enough to convince people.
And people often say, well why was he so on water?
Most of the people theorizing on cholera.
And if you go to the British Library just up the road,
you'll see that there are dozens and dozens
of books written by doctors, and scientists, and loads of other people.
But they had this multi theory of disease.
Very much part of the miasma theory, which
was the non-germ theory of disease.
ALYSSA: That was the bad air, right?
ROSALIND: Yeah, bad air, nasty smells.
Very much part that was a multi causation idea.
So the concept that one thing could cause cholera, like the water.
Was very unusual.
ALYSSA: So I didn't appreciate that.
So the people who thought that miasma was mostly the cause of disease,
did they think that tainted water was a kind of additive?
ROSALIND: Well it could be that it could be tainted air,
tainted water, tainted objects.
The idea with miasma, it could come in by any route.
I mean one of the interesting things, we have
to remember Snow was doing experiments in anesthesia.
ALYSSA: Right.
ROSALIND: And so he knew the effects of inhaling things on the body.
And the main route for miasma was thought to be inhaling.
ALYSSA: OK.
ROSALIND: And so he very early on went, cholera doesn't seem like this.
it's much more you're digesting things into the digestive tract.
And this was that the beginning, if you like, of understanding that one cause
theory of disease.
In a way, the miasma theory was right in that there are lots of factors.
Your general health, your well-being.
ALYSSA: Sure.
ROSALIND: They even brought in your morality.
ALYSSA: Oh, yes.
ROSALIND: I'm afraid if you were immoral, you were going to get cholera.
But that whole idea, the holistic approach, isn't wrong as such.
But they missed out the single cause.
And people have also said, well how was Snow
set absolutely strong on this, when even William Budd, who
was a contemporary, he came up with the theory of water borne typhoid.
He also hedged his bets, but Snow didn't.
And I think it's very much because he was a very logical man,
but also you look at his life.
He starts off as a young doctor in the minefields of the north of England.
And the mines in those days were disgusting.
You go down underground, there was no sanitation.
If it rained, they'd flood.
They had no way to wash their hands, they had no toilets.
And he observed this, and commented on it, and in his -- 1849 -- he said,
you know there must be something going on.
So he was very close to the germ theory, although he was years ahead.
Before people like Robert Koch came up with the germ theory.
But he was close.
And so he was saying, it's something.
It's something to do with them not washing their hands
and ingesting it from the water.
ALYSSA: It's so interesting, because in the course
we have a lot of examples where we go from people
kind of collecting data and information, to sort of making empirical theories.
Like looking at statistical regularities,
to then having like a real theory with the causation.
And so in this case, right, it's the germ theory
that came way after John Snow.
And just yesterday we were talking to people in Cambridge about Isaac Newton.
And there, we have Galileo in 1610 saying, you know,
this going around this, and the moons are going around Jupiter,
and Jupiter is going around the sun, and the Earth's going around.
And he's putting it all together, he's like there
must be something holding all of it, but no gravity, right?
There's no conception of gravity until many decades
later, when Newton comes along.
And it's the same.
When you told the story, just like that.
It strikes me that John Snow is like, you know,
there's something going on here.
And then he moves on to this data collection phase.
ROSALIND: And because he's so empirical.
So OK, he's observed the miners, and that's where cholera hits England.
When it comes in, in the 1830s, it comes in via the trading ships that
go primarily to the north of England.
And so the first cases are seen up there in Northumbria.
And so he's had firsthand knowledge of cholera,
he's seen that it spreads like wildfire, but in particular circumstances.
I mean one of the problems with cholera, is because it is not that contagious
person to person, people would observe you could be nursing someone
and not catch it.
And yet you'd be living in an area, of course
we now know you're living in an area where the water is polluted,
and a lot of people will catch it.
And they couldn't work that out.
Of course it fitted with the miasma idea that the air
was bad in those poor areas, and that's why
people moved up to the hillier areas.
And it was logical for them.
But the other thing that Snow did that I think
was absolutely remarkable, when he's comparing the water companies.
And it was a little bit like cable TV, water companies went rushing in.
In one street, you could have three or four water companies.
ALYSSA: It is like cable companies, yes.
ROSALIND: Yeah.
And it was the beginning, if you like, of running water.
And London, as a very advanced city in some ways,
was going to be very early in adopting water.
But even at that time, they could only have piped water
for a couple of hours a day.
And remember, it had to be pumped.
And so they hadn't got the concept of running it continuously,
and they didn't think people should work on a Sunday, for instance.
So, day of rest.
So basically, no water on a Sunday.
So it was all a bit haphazard.
And some companies were drawing the water directly
from the dirtiest part of the Thames.
Whereas other companies, like in Soho, would go from the north of London.
There was something called the New River Company,
and they were taking water from the much cleaner stretches,
beyond the industrialized city.
And the irony for Soho, where this great outbreak took place,
was that in general, the piped water was pretty good.
And Snow had to go right down to south London, near the Thames,
where the Vauxhall Lambeth companies in the South
were drawing it straight out of the Thames to actually do this work.
And I think it's brilliant deduction that he would compare the two.
And you might say, well, how would he know?
Because most of these people were renting.
They wouldn't know--
ALYSSA: --where their water came from.
ROSALIND: Well, he used a chemical test to see how much salt was in it.
[INAUDIBLE] the analysis was not microbiological at all at this stage.
It's mostly chemical.
So that even at the end of the 19th century,
people are doing chemical analysis.
And so actually having a high salt content--
and if in doubt, he would just taste it and, of course,
the water that came from the estuary, Thames
being a tidal river coming straight in from the sea.
And then that would be saltier and the saltier water right down in the estuary
where all the boats were, that was the filthiest.
So he was actually able to very accurately draw these tables up.
ALYSSA: So just to review than, what he was trying to do
is when you said that he called it a great experiment,
he was trying to isolate possible causes.
And he, of course, was more interested in water than other causes
because he was semi-convinced from the beginning, right?
ROSALIND: Yeah.
ALYSSA: And so then if the biggest difference between peoples' lives
was where they got their water, that to him was great evidence, right?
ROSALIND: Yes.
And there was even greater evidence, unfortunately,
when you had this terrible outbreak in 1854 where huge numbers of people
started dying in this very concentrated area and could
he show that that was from the water.
But neither one of these things completely
convinced the other people that were studying what we
would call public health then, right?
He was very disappointed that his work in comparing the water and the showing
that there was less cholera if your water comes
from a cleaner stretch of the Thames, which to him seemed very self-evident.
ALYSSA: Right
ROSALIND: So-- but imagine the miasma people, with their world view
very much-- like probably we are wrong about a lot of things today.
ALYSSA: No, it's actually kind of like the earth
being at the center of the solar system rather than the sun.
It reminds me again of yesterday.
ROSALIND: Yes, very much.
It links in very much with gravity.
And of course with astronomy, and people have often observed,
the logical thing is to assume that there's a dome over the earth.
You look up and that's what it looks like.
ALYSSA: Yeah, and if the air smells bad, you're getting sick from the air.
ROSALIND: Exactly.
ALYSSA: Right.
And of course, there was some truth in.
I mean, dirty air is bad for you.
ROSALIND: Right.
But it was all muddled up with this idea.
And it was such a shame.
Poor Snow, he'd done all this work.
He was continuing to do it.
He was convinced that if there was an outbreak, if you like,
that would be the great experiment because--
and he was expecting it to be in South London.
There'd been--
ALYSSA: Because the water was terrible there.
ROSALIND: Yeah, there'd been several outbreaks.
So when a few streets from where he lived in Soho, he
hears of this outbreak, he's excited, but not
just because it's on his doorstep.
He's already interested in pumps.
A few other people in the country have said, it's funny,
but it seems to be everyone who's drunk the pump water and people have ignored
it.
But Snow has thought, wow--
ALYSSA: That could be it.
ROSALIND: And when he sees a sudden outbreak-- now we
call it a point source epidemic curve with all the cases
appearing very, very quickly, single source, perhaps a transitory one.
Well, he recognized, without having epidemic curves and stuff like
we have today, he recognized that this was a most unusual outbreak.
This wasn't typical cholera.
Cholera usually spread insidiously.
Obviously, it's in the water periodically.
It's-- and people with very poor hygiene really haven't been able to wash
their hands at all.
But otherwise, it takes a few days, each case.
The incubation is quite long.
But with this, they're all getting sick over a weekend,
and that means they've all got it from the single source.
ALYSSA: And let me just say that we've talked to Dan Goldman
from our School of Public Health at Harvard about the cholera epidemic.
And then of course, I've read [INAUDIBLE] work
because he's so fascinated by this map.
But he removes the Voronoi line that we can talk about later.
ROSALIND: Yeah.
ALYSSA: But then Steven Johnson's book, which
you mentioned, is the compilation of the work actually
of much scholarship about John Snow.
But in all of those, it seems to point to this story
where baby Lewis, the poor baby who gets sick first, her diapers or excrement
or whatever it was winds up in the cesspool in the basement
or in the street outside the address that's right next to the well
for the Broad Street pump.
Is that account--
ROSALIND: Yes.
ALYSSA: --true?
ROSALIND: What we understand now was that we now call that the--
ALYSSA: Patient zero.
ROSALIND: Yes, patient zero.
Basically, there may well have been some cases before.
But in terms of this sudden outbreak and the reason why
it became such a violent outbreak is this house, which
is now the public house-- it was a the pub. [INAUDIBLE]
ALYSSA: We will visit the pub later.
ROSALIND: All right, OK.
This house, like many of the others, has a cesspool for drainage.
Usually this would be in the cellar, either in the front of the house
or just at the back.
And it's interesting because social changes are coming in at this time.
It had been quite profitable for landlords to empty these cesspools
and sell the sludge--
ALYSSA: As fertilizer.
ROSALIND: --for fertilizer.
But at this point in the 1850s, Britain has discovered another source of niter
in bird guano.
ALYSSA: Oh, bird--
ROSALIND: Yep, and much easier, because anyone who knows bird poo,
it's drier and easier to deal with.
ALYSSA: Smells less bad.
ROSALIND: It's just easier.
And although the explosive industry has been using the nitrogen [INAUDIBLE]
in fuses, this is a much better source.
So suddenly, it becomes much less economically profitable--
ALYSSA: To collect the waste.
ROSALIND: --to collect the waste unless you pay.
Now, the wealthy, the middle classes, the upper classes, they go on paying.
I mean, who doesn't want their cesspool emptied?
ALYSSA: Right.
ROSALIND: But the poor who are renting, the landlords can-- there's no law.
The landlords can choose.
They have tried to bring in legislation.
1848 Public Health Act-- they try and bring
it in that you must keep the streets clean.
You must empty cesspits.
But there's little enforcement.
These are the early days of public health--
ALYSSA: When is the year of the famous great stink.
ROSALIND: That's 1858.
ALYSSA: 1858.
ROSALIND: That's four years--
ALYSSA: So that's after.
ROSALIND: Yeah, and in fact, ironically, it's only when the great stink occurs--
and if you like, the great and the good are inconvenienced by sewage--
that they actually rush through the legislation
to build better sewers in London.
I mean, London has-- it's the first city in the world
to reach population of a million.
It's rapidly growing in those early 1800s.
You can imagine it did have service, but they were very rapidly inadequate.
And unlike some other cities where they were trying to plan ahead,
London was just kind of growing.
And that was a huge problem.
So then-- so you have the cesspools overflowing more than they did before.
So you can imagine this Broad Street in the center
of Soho, predominantly poor people, where most of the cesspools
are just left until it's really disgusting
and the landlords have to act.
And you have this little girl on a very hot night getting what they call
exhaustive diarrhea, which is cholera.
Gives you this very runny liquid diarrhea.
And the poor mother-- I mean, I think a couple of things could have happened.
Most of these were families living in one room.
Often to get to the cesspool, you had to go through another person's home.
If their place was around at the front, she could just--
ALYSSA: Throw it out the window.
ROSALIND: --throw it out the window.
ALYSSA: Yeah.
ROSALIND: The papers would be pretty disgusting and the pump was very near.
So whether it came through the cesspool, where obviously
quite a bit of the-- perhaps during the day,
she'd managed to get down to it, and at night just draining down.
These were shallow wells.
ALYSSA: How deep roughly would the water--
ROSALIND: 20 foot or so, really very shallow.
London, of course, one of the reasons why
it became such a great city-- no shortage of water.
I mean, [INAUDIBLE] when the Romans founded the main city of London
2000 years ago, it was partly because of the tidal river bringing the ships in
and the ample water.
Basically, we've got a very high water table,
and if you dug anywhere in London, you'd be able to have a shallow well.
ALYSSA: So the Romans are famous for all their aqueducts
and actually for some amount of sewer system.
So did they have a system in place?
ROSALIND: They did.
ALYSSA: They did?
ROSALIND: Yeah.
Mainly, it was based on the little rivers
that drained into the great river Thames so that they
would use those as their sewer system.
ALYSSA: Did they cover them up, or that was much later?
ROSALIND: They did have covered sewers, but not-- after all, London
wasn't like Rome.
They did have water suppression--
ALYSSA: We have uncovered that.
ROSALIND: And they have toilets, you know, latrine systems.
But very little evidence of that survives,
which suggests to me that it was at a fairly basic level.
ALYSSA: I just have to ask you one really weird question.
So I was at Ephesus once and I saw the ruins,
in a Roman ruin, of a social toilet, where
there were people sitting next to each other using the toilet, chatting.
Is that like a common thing in the Roman Empire?
ROSALIND: Oh, absolutely.
ALYSSA: Really?
OK, yeah.
ROSALIND: Yeah, yeah.
Because even though they were very sophisticated, it was still quite a big
deal to have proper sanitation.
ALYSSA: And they did take the waste away from those public toilets, yeah.
ROSALIND: Yeah, they would rinse them.
They didn't have flushing loos.
They would have slaves to rinse the loos for them
and they didn't have toilet paper.
They used sponged.
That's a whole new course, isn't it?
Yeah, really.
It was so interesting.
But we have uncovered a few.
You know Hadrian's Wall, which is the wall they built between England
and Scotland to keep the pits out.
ALYSSA: Right.
ROSALIND: And we found on that wall.
We found some primitive evidence of the soldiers' latrines.
And they were all communal.
Yeah.
ALYSSA: Yeah, and so did the Romans have any idea, do you know,
of how important it was to keep water supplies clean?
ROSALIND: Yes, they did.
They had-- I mean, they had the great sewer that's still in use today.
I think it's called the Cloaca Maxima.
ALYSSA: I don't know.
ROSALIND: But anyway, it's still in use.
The Romans were great sewer builders in that sense.
They didn't go, as far as we know, anything like that in London.
ALYSSA: But in terms of being able to predict that bad air or bad water
or whatever would make you ill, right?
Because the course is about prediction.
So the reason that we come back to John Snow, that we're
so interested in John Snow in building the course,
is that, yeah, there were Romans with sewers.
There were other people who were clean, et cetera.
But people hadn't made the connection between that you
could find kind of an underlying cause by doing
a kind of statistical canvassing of an outbreak
and then trying to figure out what the cause of a disease
is so that you could predict such conditions would cause
that disease in the future, right?
And so John Snow is given credit in a lot of popular material
that I've read, anyway, as being the person who first did that,
who used this cholera epidemic to say, you know, I think this is the cause,
but [INAUDIBLE] I'm going to collect all this data to see whether that
could be the most likely cause.
And so is it true that he's the first person who did that, or not really?
ROSALIND: He's definitely one of the first.
ALYSSA: OK.
ROSALIND: I think you have to be really careful.
We think these are all joint, collaborative things.
He was very fortunate to have some very able people working with him.
It was the local curate, Henry Whitehead, who did a lot of the door
to door searches, which actually established the pattern of the deaths.
And although Snow was remarkable in being
very ahead in the deductive reasoning and so on,
I wouldn't say he was like the only one.
And although, yes, he used the Voronoi technique to show the distance--
ALYSSA: The walking distances.
ROSALIND: Yeah, the walking distance.
He was obviously a brilliant man.
He also was one of the pioneers of dose response relationships--
ALYSSA: In his work in anesthesia.
ROSALIND: So he was absolute remarkable man.
But one of the reasons why his memory has been criticized
is that people are going, well, it wasn't just him.
And of course, it wasn't just him.
I think in a way, with the history of epidemiology,
we don't have that many icons.
So we may have piled a lot on the memory of Snow.
But certainly, he was one of the first.
ALYSSA: And you mentioned something earlier that's really important now.
And you know, I know we have these questions
and we're going to weave them all in somehow into our conversation.
But you mentioned something earlier about the difference
between how epidemiology is regarded in the UK and in the US.
And in the US, it's really regarded as a partnership, everything
from microbiology and the sort of statistical modeling
at both the small scales and then the large scales.
And when he said Henry Whitehead, it makes
me think of the kind of human data collection
and the human element in epidemiology.
And we had a question here that epidemiology
is a little bit unlike, say, gravity in that
it actually depends on human behavior.
And so it seems to me as an outsider that to model the spread of a disease
or predict the spread of a disease, you need
to everything from what of the genetic origins of the disease, what
are the genetic properties of the particular infecting bacteria,
if there is one, right from that level through medical manifestations of all
of that up through how is the population arranged
and how do the politics work it.
It seemed to me, anyway, that in the US, there
are people who treat public health as that kind of end to end study.
Is it really?
I mean, I think you agree that it has to be done in that way.
ROSALIND: Oh, absolutely.
ALYSSA: And then here, it's maybe a little bit different sometimes?
ROSALIND: No, I think very much now in Britain,
it's very, very much a joint enterprise.
And perhaps we took a little longer then in the states
to get that idea as joint enterprise.
Perhaps we had a few more mavericks working on their own.
I mean, the whole public teaching movement very much
started on the continent of Europe and in the states.
And we were somewhat late--
ALYSSA: Which is a little ironic, given the John Snow started it.
ROSALIND: It's ironic, but in a way.
ALYSSA: No, seriously, to go back to John Snow and this kind
of collaboration, he worked with Henry Whitehead
to assemble data about where all the deaths were and what people were doing.
ROSALIND: And he also worked with other doctors.
People often don't give those other guys the credit,
but he wasn't the only doctor in the area
and they were all working together.
And he certainly wasn't the only doctor who
thought that there might be something in this poor hygiene.
We're at the beginning of the Victorian obsession with hygiene.
We've had the Public Health Act, which, if you like,
says we must get rid of cholera by cleaning up the environment.
So they very much think that they should be sterilizing the environment.
ALYSSA: And that might have been directly worked
without even figuring out that it was from water if the environment was
super clean.
ROSALIND: Because they're trying to suppress smells and effluvia,
you know, the whole idea of these noxious things.
Even at the end of the century when they have an outbreak of infection,
they're dousing the streets with chloride of lime,
I suspect in the states as well in the big cities.
Because it was the whole approach-- when we started treating water,
where now in many countries, we have chlorine, of course,
and other treatments to clean water.
But water treatment started with treating the sewage,
and they only treated the sewage.
And it's quite ironic.
ALYSSA: Not the water that you drink.
ROSALIND: The stuff that's gone out because they wanted it not to smell.
So at the same time, if you like, as Snow is doing his researches,
there is this growing fear of dirty areas.
And so it's not that people don't think that dirty water could make you sick.
They don't quite understand why it should be something in the water.
It's very hard for us to put ourselves into a mindset of such
a fundamentally different thing.
ALYSSA: Did Snow-- I also read accounts of him holding up the water and looking
to see if it was cloudy--
ROSALIND: Yes he did.
ALYSSA: --and trying to examine it.
But did he have a microscope?
ROSALIND: I don't know if he actually possessed one himself.
He certainly had friends and colleagues.
There's a guy called [? Hassle ?] who did look down a microscope.
And if I-- Snow gave him some samples and he looked down and saw things that
might be--
ALYSSA: Cholera is in fact quite small, right?
ROSALIND: Yeah, they're little rod shaped--
ALYSSA: Yeah, and so would they have had a microscope good enough
to see them even if--
ROSALIND: Maybe-- yes, but there's a whole mess.
I mean, you have to know your modern microbiology.
If you just look at a specimen, say, of soil--
ALYSSA: There's a lot of stuff.
ROSALIND: There's a lot of stuff.
You have to know how to grow it, grow out the other things,
so that you can focus in.
And there are some organisms like the one
that causes Legionnaire's disease, Campylobacter,
that is so fastidious that we couldn't grow them
for years until we realize how to actually give them
just the right conditions.
So just looking down at a murky water, what Snow noticed
was that this water was lovely it when it came out [INAUDIBLE].
In fact, it was so lovely that people were actually using it
for local cafes and wine shops.
ALYSSA: And then there's a terrible story
about the son who sent the water to his mother and made this exceptional case.
ROSALIND: To the Mrs. Eley, who lived off in what's now West Hampstead today.
But he would-- and that's not so far, but I mean, it's sort of up the hill
all the way to the veil of health in Hampstead.
And ironically, nobody got cholera in Hampstead
except for her and her niece, who was visiting.
ALYSSA: This seems to be such ironclad evidence.
ROSALIND: Yeah, it was presented.
And Snow said, well, surely you can see that the water was taken and she took
it --
ALYSSA: Basically, we poisoned her.
ROSALIND: Well, somehow, the effluvia from Soho must have kind of floated
over-- and they actually seriously proposed-- floated over and somehow,
perhaps because she was a vulnerable old lady--
they weren't going to suggest that she was immoral-- but that somehow,
she was sort of a sitting pigeon in--
ALYSSA: I don't know.
The words climate change deniers just keep going through my head.
ROSALIND: Well, it's very interesting.
I think before we mock, I'm sure there are lots of things we hold today--
ALYSSA: Oh, of course.
ROSALIND: And we only have to think of the flat earth theory and all the rest
that until we can actually see our planet from space,
and I think a lot of people are still going, hm.
And it's the same with the miasma theory, which, can I just say,
is still alive and kicking.
You only have to look at advertisements in the TV for anything
to do with hygiene and it always emphasizes how clean it'll smell.
And that's because that's the miasma side because we as human beings
learn to think, if something smells bad, it must be--
ALYSSA: And we do think if it tastes OK, it probably was fine.
And that's not usually--
ROSALIND: And this water tastes more tame because it had a lot of salt in it
from the various certain things and also a lot of nitrogen,
nitrates, which made it fizzy.
And so it had a slight fizz.
ALYSSA: Natural sparkling water.
ROSALIND: So it was really attractive water.
But what Snow found was if you left it on a shelf for a couple of days,
it went cloudy.
Now, if you try that experiment with a glass of London water today,
it might taste a little stale after two days, but it would be perfectly OK.
ALYSSA: And is the cloudiness related to the bacteria in the water?
ROSALIND: Yeah, the cloudiness was related to the organic contamination,
which left on its own in the water main, any water
has got a small amount of bacteria in it.
It's not a pure product, even treated water.
And many people feel that that's good for us that it should be so.
But the water from that pub was seriously loaded.
So once you left that on a shelf, it would go cloudy very quickly.
I mean, that's why if something's bad, it goes up quite quickly.
ALYSSA: Yeah, that's true.
We all know this from personal experience, yes.
ROSALIND: I think it's very interesting about the miasma theory
and I think there's a lot of interesting theses to be done.
ALYSSA: It's true, people just don't like things that smell bad.
ROSALIND: No.
Well, if we take a great figure like Florence Nightingale, who
worked on the cholera outbreak at the same time
that Snow was investigating it, she never been in germ theory,
and she died in 1910.
ALYSSA: Really?
ROSALIND: She lived her entire career --
ALYSSA: Florence Nightingale never believed in the germ theory?!
ROSALIND: She believed--
ALYSSA: --right up until 1910.
ROSALIND: Open the windows, get ventilation in, and scrub everything.
She believed in-- she made a lot of difference out in the Crimean War
just by insisting that everything should be clean.
And right at the end of her career when she
was forced to accept that they had found these germs.
But what she maintained was that if you were locked up
in an unventilated, dirty place, you could generate these.
They were in you.
And that's part of the miasma theory is that--
ALYSSA: That's true.
ROSALIND: It's like, you do it.
So that's why the whole morality thing came in
and that's why people would-- healthy body, healthy mind-- that basically
if you kept yourself really fit-- and there
are people who talk like this today-- that the germs, they can't affect you.
Because basically, it was considered a sort of breakdown,
not sometimes invading.
ALYSSA: At some level, right?
If your immune system is weakened because you're so sick or so unfit
or whatever, it is true that the germs can-- so
like a lot of these sort of theories, you know,
this was headed in the right direction but they're not the whole picture.
When you read very short accounts of this map
or when you see it presented in other documentaries or whatever,
you often get the impression that John Snow
is walking around Soho with a clipboard and this map
and putting dots and making this histogram as he walks around,
which is not true.
And in fact, the more scholarly accounts that I've read
make it sound like he made the whole map after, well after this was over.
ROSALIND: Yes, that's right.
ALYSSA: And so did he have a map that he was making his head?
Did he have a sketch?
Did he just use tables and have a picture in his head, or what--
ROSALIND: He was-- he was very good at drawing up tables,
and it was something, because of his work with anesthesia,
he was very good at working with compounds
and drawing up effects and things.
So he would have been making lists of the deaths
and he would have some people like the local doctors and Henry Whitehead,
the curate, collecting the death data.
ALYSSA: Does he have that materials still?
ROSALIND: I'm not sure.
ALYSSA: His records?
No.
ROSALIND: I'm not sure.
ALYSSA: No, no, OK.
ROSALIND: What's very interesting-- his notebooks,
which he kept almost every day of his life,
for the period that he's investigating this is the time he doesn't make--
he doesn't--
ALYSSA: He's too busy to write it down.
ROSALIND: He's too busy.
And what I think he was doing was not using map,
but he was collecting addresses and so on.
And when he was presenting the information to the board of inquiry,
they set up an inquiry immediately.
Because this was a very nasty outbreak with-- some important people
had died in addition to the poor.
And so he was presenting the information.
And that's when he drew the map to convince them.
ALYSSA: The map that's on this lovely John Snow Society mug.
ROSALIND: Yes, so he had-- if you like, he got the data.
And this was just another way of demonstrating it.
It wasn't how he solved the outbreak.
ALYSSA: It's so interesting because in my data visualization life,
we talk about a difference between data exploration and data explanation.
And we say that the best tools are the ones that allow you to do both.
But most scientists do draw a line between how
they explore their data and then how they present it to other people.
And so the map is really a presentation of what he had found to other people.
ROSALIND: Now, I have no idea whether he did have some kind of pins on a map.
I mean, even today, I know that we have fantastic digital mapping now.
But there is something, when you're investigating an outbreak,
and I've investigated a good few, there is something very physically attractive
and it mentally works to map it out.
It's sort of the way the human brain works.
And I think we haven't yet come over that with some of the techniques
on the screen to actually get that physical side.
Now, whether he did that, we've no idea.
I think if I was doing John Snow the movie,
I would be tempted to have somebody--
ALYSSA: Are you planning on John Snow the movie?
ROSALIND: Oh, I'd love that.
ALYSSA: I want to see that.
Except there's this character on, what is, "Game of Thrones"?
So there's a famous John Snow now on TV.
ROSALIND: Oh, I've heard.
ALYSSA: Yes.
ROSALIND: Yeah, I don't watch that.
ALYSSA: It's spelled differently.
ROSALIND: Yeah.
ALYSSA: Anyway.
ROSALIND: So the answer is, he did the map to make his case.
And I think it's very interesting that he
chose-- I went to do like a little mini-histogram
of little stacks of the deaths.
And I think that is quite extraordinary.
Certainly, there were loads of maps.
ALYSSA: And they were dot maps.
ROSALIND: They were dot maps.
And also--
ALYSSA: Not necessarily histograms.
ROSALIND: People were very interested in geology.
Remember the whole miasma made you think the environment.
A lot of doctors were very well versed in what
made up soil, what made up buildings.
They'd even get interested in architecture and designing of things.
And so they would draw very detailed maps of an outbreak area.
But that would be sort of different.
Snow, in doing this one, he's already absolutely convinced.
And so that's when he does, if you like, the Voronoi--
ALYSSA: The line--
ROSALIND: --well before it's named Voronoi of course.
So it shows you what an original mind--
ALYSSA: Just to remind everybody what that is,
that's showing a wavy line that shows the walking distance to various places
from various pumps on the map.
And he showed that this weird pattern of deaths
is all within one kind of walking distance from the Broad Street pump.
ROSALIND: And very important to know that there would
be pumps at loads of other locations.
I think on the first mug, yeah we haven't got any little marks.
But then on one of our later mugs, we-- or maybe we don't.
ALYSSA: Of the other pumps?
ROSALIND: Yeah, we actually-- not the other pumps.
We actually put the little histograms in.
ALYSSA: Oh, OK.
ROSALIND: But basically, that's kind of remarkable because that in itself
shows you.
But on one of his earlier maps, I'm pretty sure that there
are the other pumps shown as well.
So--
ALYSSA: Yeah, definitely.
They're here.
ROSALIND: Yeah, so that people could actually see.
For instance, Golden Square, where there were lots of cafes and it
was the classier neighborhood-- because they had a pump.
So why were they using the Broad Street water?
ALYSSA: Tasted better.
ROSALIND: Because it tasted better.
It's a very interesting thing.
Why would sewage in water tastes good to us?
I have a tiny theory about this which may go back to the early origins of man
that when we were lost in those very early communities a long way
from home, actually, the smell of human sewage, which we're very highly
evolved, we can smell the molecules from sewage compounds at an incredibly
small level.
ALYSSA: I noticed that on a train yesterday--
ROSALIND: It must have some kind of evolutionary.
ALYSSA: --when I moved.
ROSALIND: So I hate to say this, but we were probably--
once you tested the water and tasted a bit sweet,
you know you're near the village.
Maybe-- something like that.
And so in a way, people have written about the disgust
that we now feel for if you knew there was sewage in the water,
you wouldn't drink it.
Because these people didn't know it.
And they certainly, if they saw stuff in the water, just like us,
they'd react just like us.
ALYSSA: Yeah, I'm not going to drink that.
ROSALIND: And everybody had filters.
So they would filter the water.
They'd drink out frogs and things.
They wouldn't be drinking it with all sorts of junk in it.
But basically, if the water looked good-- and microscopes, as you say,
were pretty primitive.
And we know Pasteur, he helps to save the British brewery history
where he shows his friend Whitbread that the beer he's making
might have got contaminated.
That's 20 years later.
So it's at a particular moment in time before microscopy is fully evolving
as a proper science, before the hygiene methods have really got going.
And yet, Snow is 40 years ahead of its time.
In a way, it's tragic he didn't live to see that.
And what would he have contributed?
Masses, I think.
ALYSSA: Yes, so when you say 40 years ahead of the time
and we talked before about phenomena now that we think maybe
we understand that we're probably totally wrong about the explanation,
and then there are some cases where we think we understand a little
but we don't understand a lot, and they definitely play into stories like this.
And so the one I want to ask you about is genomics and sort
of adding the micro micro level of information
to epidemiology that you're an expert on generally.
So in other words, now when people do this kind of study,
I know that there-- there are different approaches that people take.
There are approaches where they do it purely statistically
and they look at these SERI models and the SER models
and they're just sort of saying, OK, everybody is the same
and we're going to have this infection and it's going to spread.
But then there are these other sort of more patient based models
where you look at an individual person and then you say, you know,
what's their susceptibility to this disease and is that a factor in it?
Do we know enough about genomics now to know how important that really
is in terms of if you were going to make the computer model, which we get
to later in the course, of global health or of the spread
of some particular disease?
You know, some people would say that it's
the human factors and the politics that are kind of more
important than anything else.
Other people would say it's the medical effects
and other people would say it's the sort of microbiological effects.
And so where are you on that sort of how much of this is important spectrum?
ROSALIND: Obviously, we know a lot about the human genome
and we've made huge advances.
I'd say we still don't fully understand.
We know a lot about susceptibility.
I would say, and I've always wanted this in outbreaks,
we should study the people who don't get sick.
ALYSSA: Yeah, well, Snow did.
ROSALIND: Yes.
ALYSSA: He found the brewer workers and the--
ROSALIND: Yes, he did, and that is remarkable for this period in time
that he actually looks at the people who don't get sick.
And in a way, often when we're really busy
investigating things-- Ebola, whatever it is we're
investigating-- we should be looking very much at the people who
don't get it as well as of course those people who get it
because we ought to prevent it in them.
And although we know a lot about susceptibility and we know that there
are particular loci for susceptibility to bacterial infections and viral
infections and perhaps the public don't want to know--
would you really want to know if you're susceptible to--
ALYSSA: Well, I think you don't want an oversimplified model.
I mean, we talk about climate change simulations a lot
in the latter part of the course.
And there, it's really hard to explain to people that you can't just say--
sea level rise is the best example, OK?
So you say, OK, well, what if the sea level goes up by an inch worldwide?
It's not a bathtub.
You can't just say, the water goes up, and everywhere, the coastline
recedes by whatever the angle is by an inch.
It turns out that the pressure of the water on the earth
and what the seabed have made of actually
makes it a very complicated calculation to figure out what sea level rises is,
which then complicates the modeling more that depends on the amount of water
in a particular area.
And so this interconnection between different kind of input
parameters and output parameters is something
that we try to emphasize in kind of how the computer modeling works.
And so it seems to me that the more you factor in things like susceptibility
in modeling outbreaks, the more complicated it becomes
or potentially the more accurate it becomes, but also
the harder to explain.
I mean, poor John Snow is going there saying,
look, we shipped water to this woman nowhere near the outbreak and she died.
Is that not enough information for you?
No, and so there's--
ROSALIND: No, no, they'd say, well, this was an old lady and she, you know.
ALYSSA: Right, and so the same thing--
ROSALIND: Whatever.
ALYSSA: --you say what I want to know if I'm susceptible to some disease,
my answer is I know enough people who do genomics research to know that it's not
usually.
It's a very rare case where it's one gene, and if you have that gene,
you're going to get that disease.
It's that gene combined with a lot of other things
combined with environmental conditions.
ROSALIND: Yes, I mean, if you look at the cholera in the 1854,
one of the reasons why that local area of Soho was so susceptible
is they'd had relatively clean water.
So they'd been spared a lot of the cholera exposure.
So they develop no immunity.
I mean--
ALYSSA: You can develop immunity--
ROSALIND: What we know with respect to infections
is that you get two or three years.
It varies, and of course it depends on strains.
And with viruses, it can be even longer, unless they're
very good at mutating new strains.
ALYSSA: So two or three years for what?
Sorry.
ROSALIND: Immunity.
ALYSSA: OK.
ROSALIND: So that you might get-- so for instance,
the people in South London, one of the reasons
why they don't get the cholera epidemics every year
is that the people who get the very mild infection, they get immune.
ALYSSA: This is almost the inoculation theory.
ROSALIND: Yes, and so the whole problem with infectious diseases
and one of the whole things, I think, makes the hygiene hypothesis
such an annoying idea, this idea that we should
be exposed to the real thing, one problem with that
is that a quarter of us used to die being exposed to the real thing.
And so a quarter of our children certainly
would die right up until the 1900s.
And so what was happening in that Soho area was, if you like,
the perfect experiment for Snow because you
have a genetically susceptible population that
haven't been exposed to much cholera so that when
they get a violent attack via their water supply, a load of them
are very susceptible.
And what you find in any normal outbreak when you're investigating
is that even with a very high dose of the disease,
the attack rates are relatively low.
All sorts of things-- age, previous infections.
Often, you find military personnel are very protected.
ALYSSA: Because they've been a lot of places.
ROSALIND: They've been to a lot of places.
And sometimes, they've a lot of vaccines as well and they're fit
and they're very tough.
And in fact, you get these fallacies of stats
where if your controls contain too many of these kind of super fit people,
you get a very poor impression.
ALYSSA: So you do have to account for all those other.
ROSALIND: You do, and the fact that nutrition
would have been very badly for a lot of those people.
They'd have been eating very poorly.
Probably, they weren't well-hydrated.
Because if you-- the way they did it was the water
would come in for two hours a day.
They'd fill the water tub in the house.
There'd probably be only one tap.
And then the rest of the hands, for the rest of the day,
they'd come and dip their pot saying.
And by the end of the day, it would probably be pretty dirty.
And after a couple of days, because they wouldn't fill it every day--
they'd fill it and then they'd wait a couple of days
and they'd fill it again.
And so in fact, at the brewery, they had such a system.
But most of the workers were paid in beer.
ALYSSA: Right
ROSALIND: And at that time, they had a kind
of very dilute beer that was suitable for children
as well so that they actually closed off the communal water very early on so
that the workers were particularly protected at the brewery.
And the workhouse, people said, well, if they were susceptible,
the people in the workhouse would be old and poor and poorly nourished.
Surely, they'd ahve--
ALYSSA: They did not die.
ROSALIND: --gone down like skittles.
Why didn't they?
ALYSSA: They had their own well.
ROSALIND: Because they had their own well.
And that shows you that even though they would have been highly susceptible,
it shows you the cholera is not that catching.
And that since it wasn't in their water-- and of course,
being in the workhouse, they wouldn't go out much.
So the poor things, they might have yearned to go
and they'd heard about the John Snow-- not John Snow, the broad street pump.
But they'd not be allowed out.
ALYSSA: Good for them, good for them.
I have one last question.
ROSALIND: OK.
ALYSSA: In terms of prediction, do you think that we can get to a point
now where we would reliably be able to predict
who would be susceptible to cholera?
Would we be able to test people to predict on an individual basis
whether people would be--
ROSALIND: Yeah, I think.
ALYSSA: Like, can you find immunity to cholera in somebody's blood test?
ROSALIND: Yes.
ALYSSA: You can.
ROSALIND: And I think it's highly likely that in the future,
we'd have to get the social problem sorted out, insurance and so on.
But I think it's highly likely that we are able to predict particularly people
at particular risk of infections.
We know already that there are several loci that
make you more susceptible to certain bacteria like the ones
that cause meningitis and that those people would
be priority candidates for vaccination.
So I think it's highly likely in maybe 100 years.
I don't think it'll happen very quickly because the test would probably
be expensive if they're based on genomic tests.
So, yeah, it's possible.
ALYSSA: OK, good.
ROSALIND: We're going to get there.
ALYSSA: Good, we'll end on an up note.
OK, thank you.
본 과정은 Harvard University(하버드 대학교)의 수강과목 "PredictionX: John Snow and the Cholera Outbreak of 1854" 입니다.
John Snow and the Cholera Outbreak of 1854 offers a preview of a new HarvardX offering called "PredctionX," which looks at how humans have predicted their own futures throughout recorded time. Here, we explore how a deadly outbreak of cholera in London, and John Snow's investigation of its cause, gave rise to the modern field of epidemiology. It's a fascinating story. Even if you've heard it before, you may find new facts and details here that we've uncovered through expert interviews and map analysis. We hope you enjoy it.
The full set of PredctionX offerings, to be released on edX in installments during 2016 and 2017, will begin with the story of how preists in Ancient Mesopotamia used sheep entrails to fortell the future, and will end by explaining how modern-day scientists use computers to predict the future of our world's climate, economy, health, and place in the Universe. For more information, check out the sneak peek of the rest of PredictionX at the end of this course and stay tuned for updates at #PredictionX on twitter, and here on edX. Twenty-five faculty are working together to create this course, from across Harvard, and beyond.
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