The cause is a micro-organism identified by Koch in 1883 (see PARASITIC
DISEASES). For some years it was called the "comma bacillus," from its
supposed resemblance in shape to a comma, but it was subsequently found
to be a vibrio or spirillum, not a bacillus. The discovery was received
with much scepticism in some quarters, and the claim of Koch's vibrio to
be the true cause of cholera was long disputed, but is now universally
acknowledged. Few micro-organisms have been more elaborately
investigated, but very little is known of its natural history, and its
epidemiological behaviour is still surrounded by obscurity. At an
important discussion on the subject, held at the International Hygienic
Congress in 1894, Professor Gruber of Vienna declared that the deeper
investigators went the more difficult the problem became, while M. Elie
Metschnikoff of the Pasteur Institute made a similar admission. The
difficulty lies chiefly in the variable characters assumed by the
organism and the variable effects produced by it. The type reached by
cultivation through a few generations may differ so widely from the
original in appearance and behaviour as to be hardly recognizable,
while, on the other hand, of two organisms apparently indistinguishable
one may be innocuous and the other give rise to the most violent
cholera. This variability offers a possible explanation of the frequent
failure to trace the origin of epidemic outbreaks in isolated places. It
is commonly assumed that the micro-organism is of a specific character,
and always introduced from without, when cholera appears in countries or
places where it is not endemic. In some cases such introduction can be
proved, and in others it can be inferred with a high degree of
probability, but sometimes it is impossible to trace the origin to any
possible channel of communication. A remarkable case of this kind
occurred at the Nietleben lunatic asylum near Halle, in 1893, in the
shape of a sudden, explosive and isolated outbreak of true Asiatic
cholera. It was entirely confined to the institution, and the peculiar
circumstances enabled a very exact investigation to be made. The facts
led Professor Arndt, of Greifswald, to propound a novel and interesting
theory. No cholera existed in the surrounding district and no
introduction could be traced, but for several months in the previous
autumn diarrhoea had prevailed in the asylum. The sewage from the
establishment was disposed of on a farm, and the effluent passed into
the river Saale above the intake of the water-supply for the asylum.
Thus a circulation of morbid material through the persons of the inmates
was established. Dr Arndt's theory was that by virtue of this
circulation cholera was gradually developed from previously existing
intestinal disease of an allied but milder type. The outbreak occurred
in winter, and coincided with the freezing of the filter-beds at the
waterworks. The theory is worth notice, because a similar relation
between the drainage and the water-supply frequently exists in places
severely attacked by cholera, and it has repeatedly been observed that
the latter is preceded by the prevalence of a milder form of intestinal
disease. The inference is not that cholera can be developed _de novo_,
but that the type is unstable, and that a virulent form may be evolved
under favourable conditions from another so mild as to be unrecognized,
and consequently undetected in its origin or introduction. This is quite
in keeping with the observed variability of the micro-organism, and with
the trend of modern research with regard to the relations between other
pathogenic germs and the multifarious gradations of type assumed by
other zymotic diseases. The same thing has been suggested of diphtheria.
Epidemicity.
Cholera is endemic in the East over a wide area, ranging from Bombay to
southern China, but its chief home is British India. It principally
affects the alluvial soil near the mouths of the great rivers, and more
particularly the delta of the Ganges. Lower Bengal is pre-eminently the
standing focus and centre of diffusion. In some years it is quiescent,
though never absent; in others it becomes diffused, for reasons of which
nothing is known, and its diffusive activity varies greatly from equally
inscrutable causes. At irregular intervals this property becomes so
heightened that the disease passes its natural boundaries and is carried
east, north and west, it may be to Europe or beyond to the American
continent. We must assume that the micro-organism, like those of other
epidemic diseases, acquires greater vitality and toxic energy, or
greater power of reproduction at some times than at others, but the
conditions that govern this behaviour are quite unknown, though no
problem has a more important bearing on public health. Bacteriology, as
already intimated, has thrown no light upon it, nor has meteorology.
Some results of modern research, indeed, tend to assign increasing
importance to the relations between surface soil and certain
micro-organisms, and suggest that changes in the level of the subsoil
water, to which Professor Max von Pettenkoffer long ago drew attention,
may be a dominant factor in determining the latency or activity of
pathogenic germs. But this is largely a matter of conjecture, and, so
far as cholera is concerned, the conditions which turn an endemic into
an epidemic disease must be admitted to be still unknown.
On the other hand, the mode of dissemination is now well understood.
Diffusion takes place along the lines of human intercourse. The poison
is carried chiefly by infected persons moving from place to place; but
soiled clothes, rags and other articles that have come into contact with
persons suffering from the disease may be the means of conveyance to a
distance. There is no reason to suppose that it is air-borne, or that
atmospheric influences have anything to do with its spread, except in so
far as meteorological conditions may be favourable to the growth and
activity of the micro-organisms. Beyond all doubt, the great manufactory
of the poison is the human body, and the discharges from it are the
great source of contagion. They may infect the ground, the water, or the
immediate surroundings of the patient, and so pass from hand to hand,
the poison finding entrance into the bodies of the healthy by means of
food and drink which have become contaminated in various ways. Flies
which feed upon excreta and other foul matters may be carriers of
contagion. Of all the means of local dissemination, contaminated water
is by far the most important, because it affects the greatest number of
people, and this is particularly the case in places which have a public
water-supply. A single contaminated source may expose the entire
population to danger. All severe outbreaks of an explosive character are
due to this cause. It is also possible that the cholera poison
multiplies rapidly in water under favourable conditions, and that a
reservoir, for instance, may form a sort of forcing-bed. But it would be
a mistake to regard cholera as purely a water-borne disease, even
locally. It may infect the soil in localities which have a perfectly
pure water-supply, but have defective drainage or no drainage at all,
and then it will be found more difficult to get rid of, though less
formidable in its effects, than when the water alone is the source of
mischief. In all these respects it has a great affinity to enteric
fever. With regard to locality, no situation can be said to be free from
attack if the disease is introduced and the sanitary conditions are bad;
but, speaking generally, low-lying places on alluvial soil near rivers
are more liable than those standing high or on a rocky foundation. Of
meteorological conditions it can only be said with certainty that a high
temperature favours the development of cholera, though a low one does
not prevent it. In temperate climates the summer months, and
particularly August and September, are the season of its greatest
activity.
Western diffusion.
Cholera spreads westwards from India by two routes--(1) by sea to the
shores of the Red Sea, Egypt and the Mediterranean; and (2) by land to
northern India and Afghanistan, thence to Persia and central Asia, and
so to Russia. In the great invasions of Europe during the 19th century
it sometimes followed one route and sometimes the other. It was not till
1817 that the attention of European physicians was specially directed to
the disease by the outbreak of a violent epidemic of cholera at Jessore
in Bengal. This was followed by its rapid spread over a large portion of
British India, where it caused immense destruction of life both among
natives and Europeans. During the next three years cholera continued to
rage all over India, as well as in Ceylon and others of the Indian
islands. The disease now began to spread over a wider extent than
hitherto, invading China on the east and Persia on the west. In 1823 it
had extended into Asia Minor and Russia in Asia, and it continued to
advance steadily though slowly westwards, while at the same time fresh
epidemics were appearing at intervals in India. From this period up till
1830 no great extension of cholera took place, but in the latter year it
reappeared in Persia and along the shores of the Caspian Sea, and thence
entered Russia in Europe. Despite the strictest sanitary precautions,
the disease spread rapidly through that whole empire, causing great
mortality and exciting consternation everywhere. It ravaged the northern
and central parts of Europe, and spread onwards to England, appearing in
Sunderland in October 1831, and in London in January 1832, during which
year it continued to prevail in most cf the cities and large towns of
Great Britain and Ireland. The disease subsequently extended into
France, Spain and Italy, and crossing the Atlantic spread through North
and Central America. It had previously prevailed in Arabia, Turkey,
Egypt and the Nile district, and in 1835 it was general throughout North
Africa. Up till 1837 cholera continued to break out in various parts of
the continent of Europe, after which this epidemic disappeared, having
thus within twenty years visited a large portion of the world.
About the year 1841 another great epidemic of cholera appeared in India
and China, and soon began to extend in the direction traversed by the
former, but involving a still wider area. It entered Europe again in
1847, and spread through Russia and Germany on to England, and thence to
France, whence it passed to America, and subsequently appeared in the
West Indies. This epidemic appears to have been even more deadly than
the former, especially as regards Great Britain and France. A third
great outbreak of cholera took place in the East in 1850, entering
Europe in 1853. During the two succeeding years it prevailed extensively
throughout the continent, and fell with severity on the armies engaged
in the Crimean War. Although widely prevalent in Great Britain and
Ireland it was less destructive than former epidemics. It was specially
severe throughout both North and South America. A fourth epidemic
visited Europe again in 1865-1866, but was on the whole less extensive
and destructive than its predecessors.
By some writers the epidemic of 1853 is regarded as a recrudescence of
that of 1847. The earlier ones followed the land route by way of
Afghanistan and Persia, and took several years to reach Europe. That of
1865 travelled more rapidly, being carried from Bombay by sea to Mecca,
from there to Suez and Alexandria, and then on to various Mediterranean
ports. Within the year it had not only spread extensively in Europe,
but had reached the West Indies. In 1866 it invaded England and the
United States, but during the following year it died down in the West.
The subsequent history of cholera in Europe may be stated
chronologically.
_1860-1874._--This invasion was traced to the great gathering of
pilgrims at Hardwar on the Upper Ganges in the month of April 1867. From
there the returning pilgrims carried it to the Punjab, Kashmir and
Afghanistan, whence it spread to Persia and the Caspian, but it did not
reach Russia until 1869. During the next four years a number of
outbreaks occurred in central Europe, and notably one at Munich in the
winter of 1873. The irregular character of these epidemics suggests that
they were rather survivals from the pandemic wave of 1867 than fresh
importations, but there is no doubt that cholera was carried overland
into Russia in the manner described.
_1883-1887._--This visitation, again, came by the Mediterranean. In 1883
a severe outbreak occurred in Egypt, causing a mortality of above
25,000. Its origin remained unknown. During this epidemic Koch
discovered the comma bacillus. The following year cholera appeared at
Toulon. It was said to have been brought in a troopship from Saigon in
Cochin-China, but it may have been connected with the Egyptian epidemic.
A severe outbreak followed and reached Italy, nearly 8000 persons dying
in Naples alone. In 1885 the south of France, Italy, Sicily and Spain
all suffered, especially the last, where nearly 120,000 deaths occurred.
Portugal escaped, and the authorities there attributed their good
fortune to the institution of a military cordon, in which they have had
implicit confidence ever since. In 1886 the same countries suffered
again, and also Austria-Hungary. From Italy the disease was carried to
South America, and even travelled as far as Chile, where it had
previously been unknown. In 1887 it still lingered in the Mediterranean,
causing great mortality in Messina especially. According to Dr A.J.
Wall, this epidemic cost 250,000 lives in Europe and at least 50,000 in
America. A particular interest attaches to it in the fact that a
localized revival of the disease was caused in Spain in 1890 by the
disturbance of the graves of some of the victims who had died of cholera
four years previously.
_1892-1895._--This great invasion reverted again to the old overland
route, but the march of the disease was of unprecedented rapidity.
Within less than five months it travelled from the North-West Provinces
of India to St Petersburg, and probably to Hamburg, and thence in a few
days to England and the United States. This speed, in such striking
contrast to the slow advance of former occasions, was attributed, and no
doubt rightly, to improved steam transit, and particularly the
Transcaspian railway. The progress of the disease was traced from place
to place, and almost from day to day, with great precision, showing how
it moves along the chief highways and is obviously carried by man. The
main facts are as follows:--Cholera was extensively and severely
prevalent in India in 1891, causing 601,603 deaths, the highest
mortality since 1877. In March 1892 it broke out at the Hardwar fair, a
day or two before the pilgrims dispersed; on the 19th of April it was at
Kabul, on the 1st of May at Herat, and on the 26th of May at Meshed.
From Meshed it moved in three directions--due west to Teheran in Persia,
north-east by the Transcaspian railway to Samarkand in Central Asia, and
north-west by the same line in the opposite direction to Uzun-ada on the
Caspian Sea. It reached Uzun-ada on the 6th of June; crossed to Baku,
June 18th; Astrakhan, June 24th; then up the Volga to Nizhniy-Novgorod,
arriving at Moscow and St Petersburg early in August. The part played by
steam transit is clear from the fact that the disease took no longer to
travel all the way from Meshed to St Petersburg by rail and steamboat
than to traverse the short distance from Meshed to Teheran by road. On
the 16th of August cases began to occur in Hamburg; on the 19th of
August a fireman was taken ill at Grangemouth in Scotland, where he had
arrived the day before from Hamburg; and on the 31st of August a vessel
reached New York from the same port with cholera on board. On the 8th of
September the disease appeared in Galicia, having moved somewhat slowly
westwards across Russia into Poland, and on the 26th of September it was
in Budapest. Holland and Servia were also attacked, while isolated cases
were carried to Norway, Denmark and Italy. Meanwhile two entirely
separate epidemics were in progress elsewhere. The first was confined to
Arabia and the Somali coast of Africa, and was connected with the
remains of an outbreak in Syria and Arabia in 1890-1891. The second
arose mysteriously in France about the time when the overland invasion
started from India. The first known case occurred in the prison at
Nanterre, near Paris, on the 31st of March. Paris was affected in April,
and Havre in July. The origin of this outbreak, which was of a much less
violent character than that which came simultaneously by way of Russia,
was never ascertained. Its activity was confined to France, particularly
in the neighbourhood of Paris, together with Belgium and Holland, which
was placed between two fires, but escaped with but little mortality. The
number of persons killed by cholera in 1892, outside of India, was
reckoned at 378,449, and the vast majority of those died within six
months. The countries which suffered most severely were as
follows:--European Russia, 151,626; Caucasus, 69,423; Central Asian
Russia, 31,804; Siberia, 15,037--total for Russian empire, 267,890;
Persia, 63,982; Somaliland, 10,000; Afghanistan, 7,000; Germany, 9563;
France, 4550; Hungary, 1255; Belgium, 961. Curiously enough, the south
of Europe, which had been the scene of the previous epidemic visitation,
escaped. The disease was of the most virulent character. In European
Russia the mortality was 45.8% of the cases, the highest rate ever known
in that country; in Germany it was 51.3%; and in Austria-Hungary, 57.5%.
Of all the localities attacked, the case of Hamburg was the most
remarkable. The presence of cholera was first suspected on the 16th of
August, when two cases occurred, but it was not officially declared
until the 23rd of August. By that time the daily number of victims had
already risen to some hundreds, while the experts and authorities were
making up their minds whether they had cholera to deal with or not.
Their decision eventually came too late and was superfluous, for by the
27th of August the people were being stricken down at the rate of 1000 a
day. This rate was maintained for four days, after which the vehemence
of the pestilence began to abate. It gradually declined, and ceased on
the 14th of November. During those three months 16,956 persons were
attacked and 8605 died, the majority within the space of a few weeks.
The town, ordinarily one of the gayest places of business and pleasure
on the continent, became a city of the dead. Thousands of persons fled,
carrying the disease into all parts of Germany; the rest shut themselves
indoors; the shops were closed, the trams ceased to run, the hotels and
restaurants were deserted, and few vehicles or pedestrians were seen in
the streets. At the cemetery, which lies about 10 m. from the town, some
hundreds of men were engaged day and night digging long trenches to hold
double rows of coffins, while the funerals formed an almost continuous
procession along the roads; even so the victims could not be buried fast
enough, and their bodies lay for days in sheds hastily run up as
mortuaries. Hamburg had been attacked by cholera on fourteen previous
occasions, beginning with 1831, but the mortality had never approached
that of 1892; in the worst year, which was 1832, there were only 3687
cases and 1765 deaths. The disease was believed to have been introduced
by Jewish emigrants passing through on their way from Russia, but the
importation could not be traced. The Jews were segregated and kept under
careful supervision from the middle of July onwards, and no recognized
case occurred among them. The total number of places in Germany in which
cholera appeared in 1892 was 269, but it took no serious hold anywhere
save in Hamburg. The distribution was chiefly by the waterways, which
seem to affect a larger number of places than the railways as carriers
of cholera. In Paris 907 persons died, and in Havre 498. Between the
18th of August and the 21st of October 38 cases were imported into
England and Scotland through eleven different ports, but the disease
nowhere obtained a footing. Seven vessels brought 72 cases to the United
States, and 16 others occurred on shore, but there was no further
dissemination.
During the winter of 1892-1893 cholera died down, but never wholly
ceased in Russia, Germany, Austria-Hungary and France. With the return
of warm weather it showed renewed activity, and prevailed extensively
throughout Europe. The recorded mortality for the principal countries
was as follows:--Russia (chiefly western provinces), 41,047;
Austria-Hungary, 4669; France, 4000; Italy, 3036; Turkey, 1500; Germany,
298; Holland, 376; Belgium, 372; England, 139. Hardly any country
escaped altogether; but Europe suffered less than Arabia, Mesopotamia
and Persia. Cholera broke out at Mecca in June, and owing to the
presence of an exceptionally large number of pilgrims caused an
appalling mortality. The chief shereef estimated the mortality at
50,000. The pilgrims carried the disease to Asia Minor and
Constantinople. In Persia also a recrudescence took place and proved
enormously destructive. Dr. Barry estimated the mortality at 70,000. At
Hamburg, where new waterworks had been installed with sand filtration,
only a few sporadic cases occurred until the autumn, when a sudden but
limited rush took place, which was traced to a defect in the masonry
permitting unfiltered Elbe water to pass into the mains. In England
cholera obtained a footing on the Humber at Grimsby, and to a lesser
extent at Hull, and isolated attacks occurred in some 50 different
localities. Excluding a few ship-borne cases the registered number of
attacks was 287, with 135 deaths, of which 9 took place in London. It is
interesting to compare the mortality from cholera in England and Wales,
and in London, for each year in which it has prevailed since
registration began:--
+-------+------------------------+-------------------------+
| | England and Wales. | London. |
| +--------+---------------+--------+----------------+
| Year. | | Deaths per | | Deaths per |
| | Deaths.| 10,000 living.| Deaths.| 10,000 living.|
+-------+--------+---------------+--------+----------------+
| | | | | |
| 1848- | 1,908 | 1.1 | 652 | 2.9 |
| 1849 | 53,293 | 30.3 | 14,137 | 61.8 |
| | | | | |
| 1853- | 4,419 | 2.4 | 883 | 3.5 |
| 1854 | 20,097 | 10.9 | 10,738 | 42.8 |
| | | | | |
| 1865- | 1,297 | 0.6 | 196 | 0.6 |
| 1866 | 14,378 | 6.8 | 5,596 | 18.4 |
| | | | | |
| 1893- | 135 | 0.05 | 9 | 0.002 |
| 1894 | nil | nil | nil | nil |
+-------+--------+---------------+--------+----------------+
In 1894 no deaths from cholera were recorded in England, but on the
continent it still prevailed over a wide area. In Russia over 30,000
persons died of it, in Germany about 500, but the most violent outbreak
was in Galicia, where upwards of 8000 deaths were registered. In 1895 it
still lingered, chiefly in Russia and Galicia, but with greatly
diminished activity. In that year Egypt, Morocco and Japan were
attacked, the last severely. The disease then remained in abeyance until
the severe epidemic in India in 1900.