publichealth-2 B

Transcriber:	Yvonne Cherne
Brief Bio:
Date finished:	6-3-2007
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file: hph_lec2b.mp3

A History of Modern Public Health: Quarantine, part B

Welcome back. In this section we are going to have a look at
plague in a little bit more detail, because it is important to
look at this disease if we want to look at the history of the
developments of quarantine.

What you can see on this slide is an electromicroscopic image of
an ancient louse from an Egyptian mummy dated to around about
3000 B.C. And plague is caused by the bacillus yerisinia pestis,
and that is a gram-negative, nonmotile rod-like bacillus, and it
is about one to 15 microns in length. And the lifespan of that
bacillus actually varies considerably, and the lifespan depends
upon exposure to light and to temperature. So in frozen cadavers
and in the favorable climates, for example of Rhodes and Boros
(?), the bacillus might survive for up to a year. On the other
hand, it can only live a few days in the body of a putrefying
corpse or in surface soil. So you have different lengths of life
of the bacillus, and that depends, as I say, on light and
temperature.

The bacillus is highly pathogenic to man and to many animals as
well, and natural immunity to the bacillus is in fact very rare.
And it has been treated medically therapeutically since the 1940s
by antibiotics, and the most common drugs of treatment have been
streptomycin and tetracycline. As I said, it is highly pathogenic
to man and animals, and it is very common in particular in
rodents and field animals, and this has -- clearly has
implications, as we will see, for the transmission of plague,
historically. Reservoirs of plague infection were localized in
areas that are now still heavily associated with the disease
itself, namely central and northeastern China, Mongolia, the
Caspian Sea, the Himalayan foothills, and the great lakes of
central Africa. And when rats live in close proximity to humans,
there is the possibility of human infection.

And what we see here in a chronology of the Black Death from 1347
to 1352 are the routes which the disease took from those, some of
those reservoirs of the disease. So you can see that the disease
progressed along the trading caravan routes from the Far East and
made their way into the Black Sea area, and you have the first
instances of the disease in some of the Mediterranean ports that
received the luxury goods and spices and food stuffs from the Far
East, in particular Sardinia, Masinia, and Crete, and some of the
Black Sea coastal areas around Constantinople. And from those
places, we can see that the disease had a trajectory westwards
throughout the rest of southern Europe. There is evidence of the
plague in southern Spain for example, the west coast of Europe,
and Lisbon and also affecting the port cities of southern
England, London, and Bristol at a relatively early date in 1348.
And then as time progresses, we can see that there is evidence of
disease incidence in places as far north as Antwerp and later
Danzig and Krakow. So what the disease is doing is originating in
these reservoirs of plague of the Far East and making their way
across the trade routes into central and western Europe.

And that is connected to the fact that the plague vector -- or
the medium of transmission of the plague bacillus -- to humans is
the flea, is the rodent flea predominantly which imparts the
disease to humans with its bite. And the frequency of
transmission of the bacillus seems to be governed by a range of
factors. We have already spoken about the length of time and the
lifespan of the bacillus itself which is obviously one of the
main factors which governs transmission, but obviously it is
going to be related to the activity patterns of rodents, the
activity patterns of the fleas themselves, and also the activity
patterns and in particular the trading, economic, and domestic
living patterns of human beings.

And there are 4 basic forms of the plague in humans: there is
bubonic plague, septicemic plague, pneumonic plague, and pestis
minor. What we are mainly concerned with in this class on
quarantine is Bubonic and pneumonic plague outbreaks, and they
are the ones that have been the focus of most quarantine efforts.

But to talk a little bit more about plague itself, a variety of
clinical symptoms emerge after an incubation period of around
about 2 to 6 days. And you can see some of the symptoms are
listed here on the slide. We have high fever, we have malaise,
headaches, shaking and chills, and pain in the affected lymph
nodes. And that is where the term "bubonic plague" comes from:
the traditional name for "lymph nodes" is the "buboes," and these
effectively are the lymph nodes which become swollen in a very
painful process, especially in the arm pits, the neck, and the
groin. And in addition to that swelling, the face becomes flushed
or pallid and very bloated indeed. Ultimately, the buboes, the
nymphoes may break down and ulcerate and separate, and the death
often follows from these symptoms due to heart failure.

Today bubonic plague carries a mortality rate of less than 5
percent if promptly diagnosed and treated, and mortalities of
between 50 and 70 percent are not uncommon if the disease goes
untreated. The form of pandemic plague that emerged in 1347, and
which is going to be the focus of one of our examples later,
which lasted and lasted -- the pandemic lasted effectively until
the mid 19th century, in that form of plague mortality ranged
from between 30 and 80 percent. And it was not uncommon in
various outbreaks of the plague for around about 30 to 40 percent
of a village population or a town population to be completely
wiped out. So the plague, untreated, had a devastating effect on
human communities and towns, cities and villages.

Having considered plague in some detail, the next section will
consider some historical examples of quarantine.