Source:  Snow, John. British Medical Journal (November 7, 1857), pp. 934-935.

On the origin of the recent outbreak of cholera at West Ham

Letter from John Snow, M.D.

Sir,--I have no complaint to make of the criticism of my views on the above subject, which is contained in a leading article of the Journal of Oct. 3lst; but I shall be glad to be allowed to make a few remarks by way of defending my opinions, and to allude to a case in connection with the outbreak that I was not acquainted with when speaking at the Medical Society of London.

In the first instance, I should like to say that I have not clipped or shaped this outbreak of cholera to fit the bed I had made for it; on the contrary, it came and shaped itself exactly to the conclusions which I had drawn from the observance of previous epidemics. This outbreak at Abbey Row, West Ham, took place in a community supplied by a particular pump-well; the water of this well was distinctly polluted by a sewer, which receives the overflow from the cesspools of this community; the tide flows up this sewer from the Lea, and up the Lea from the Thames. Moreover, there had been one case known and registered of death from cholera on board a ship in the Thames from a port where the cholera was very prevalent, a few days before this outbreak at West Ham. In treating of the early cases of cholera in 1848, occurring by the side of the Thames, and near St. Bride's pump, a few days after the death of a seaman from Hamburgh, I gave an explanation, some years ago, precisely like that which I now offer of the outbreak at West Ham. (See London Medical Gazette, vol. xlvii, p. 1051.)

The case connected with this outbreak, of which I was not previously aware, is one investigated by Dr. Ansell. At the time of the cases at West Ham, just beyond the borders of the metropolis, there happened in the whole of London just one case, which, by suddenly attacking a person in good health, and proving rapidly fatal, showed itself to be of the true Asiatic type. This case was that of a boy, aged 14, living at Bromley, about two miles from Abbey Row; he passed this place with his father, on October 7th, on their return from a long walk. He lagged behind, which attracted his father's attention, who looked back, and saw the boy drinking at the pump above alluded to. The boy was still quite well on the evening of the following lay, but at five o'clock in the morning of the 9th, he was seized “with diarrhœa, vomiting, great prostration, darkness of surface, thirst, loss of voice,” and he died in twenty hours. This case resembles two cases which occurred at West End, near Hampstead, in persons who drank water which was conveyed in a bottle from the pump in Broad Street, Golden Square, in 1854. In such cases there can be no doubt that the very matter which produced the attack was swallowed in the water; and they may well lead to an admission like that made in the Journal of to-day, “that cholera evacuations may be conveyed from one person to another by means of water, and thus spread the disease, under certain circumstances.” But this is to let in the small end of the wedge; and when once it is admitted, without pushing it to the Feejee Islands, it is difficult to prevent its going as far as circumstances require and permit. In the inquiry into the effect of water supply in cholera in the south districts of London, which I alluded to in a recent paper, I found that in the early part of the epidemic of l854, nearly all the cases of cholera occurred amongst persons having the impure water of the Southwark and Vauxhall Company. But if like causes act in the same manner when they produce like effects, on comparing the action of the polluted pump-wells with that of the Company's water, we must conclude that, in the latter case, the cholera evacuations passed first down the sewers, then up the Thames to Battersea, and afterwards through the water-pipes to the distance often of several miles. This, however, is a route quite as long and as circuitous as from a ship at Horsleydown to the pump-well at Abbey Rowe; but for my own part, if it is acknowledged that the morbid matter of cholera can be mixed with the water of a pump-well, and remain for even a few hours without being destroyed, I see no difficulty in its passing a few miles with the tide, which moves in the river almost as fast as a person walks.

There may have been other cases of cholera in the shipping in the Thames, from the Elbe and the Baltic, besides the one registered at Horsleydown, but if there were not, it is unnecessary to suppose that the quantity of cholera poison was so limited that it all required to go up the Lea and the tidal ditch to Abbey Row; or, on the other hand, that it was so plentiful as to be distributed in every pailful of water in the Thames; something between these extremes is what the circumstances of the recent outbreak and former epidemics suggest. I am ready to admit that the greater part of any impurity emptied into the Thames might go straight up and down with the tide, and reach in a few days the salt water, which nobody can drink; but it is a fact that a part of the water of the Thames does flow up the Lea, and a part of this also up the tidal ditch to Abbey Row, carrying with it more or less of every kind, of impurity which enters the Thames.

In an inquiry which the Rev. H. Whitehead made, in continuation of that which I commenced, respecting the water of the pump near Golden Square, he was led to conclude that, at one period, hardly anyone drank of the water without being attacked with cholera. The evacuations of one patient in that instance appeared to occasion above 600 fatal attacks within the space of a very few days. When the cholera evacuations enter a large river like the Thames, the result, as might be expected, is different. In the autumn of 1848 the first case imported was followed, in a few days, by several cases at different parts of the river's banks, amongst the population using water obtained directly from the river; and these cases were followed by others more numerous, chiefly amongst the population supplied with water obtained from the Thames at Battersea and Chelsea; and the fresh cases again supplied the morbid poison for a large number, and so the epidemic went on increasing. The like events followed in 1853, but in the present year, when few persons use water which is in any way connected with the tidal part of the river, the first imported case of cholera has been followed by other cases at one point only, and the disease has not spread further.

Since the last epidemic of cholera, the water supply of a great part of London has been entirely altered. At present no water company draws its supply from any part of the Thames which is within reach of pollution by the shipping, or the sewers of the town. The water supply of London is now different from its condition at any former period, and that has happened now which has not occurred before in the history of cholera in this metropolis. On every former occasion, when cholera prevailed in Hamburgh and other ports in the north [934/935] of Europe, it extended to London; and the first cases were followed by others, and these again by more, till the disease was epidemic. This last summer and autumn cholera has again prevailed in the ports in the Baltic and the Elbe; it has again extended to London, and one well-marked imported case has been flowed by a group of cases on the borders of London, so well marked as to leave no doubt of their nature; but here the disease has left off for a period of already eighteen days, and, whatever may follow, this is a halt which occurred on no former occasion.

So far from it's being my opinion that the morbid matter of cholera is indestructible, I have from the first considered that it is very perishable, and that when mixed with water it cannot preserve its powers more than a few days; this being one cause why an epidemic often dies out so quickly. Dr. Wm. Budd advocated the same view in his able articles in the Association Medical Journal in 1854 and 1855. I believe that cholera poison, destructive as it is in certain circumstances to the human species, has many enemies, is easily destroyed, and, what is of more importance, is still more easily avoided.

I regret that I cannot enter fully into my views regarding the pathology and history of cholera in the short space to which it is necessary to confine this article; and I beg the reader to remember that, although I find it necessary to write most on that part of the subject which concerns the communication of cholera through the medium of water, its propagation by swallowing the morbid poison without this medium, plays a very important part in its progress, more especially in the crowded habitations of the poor.

I am, etc.

John Snow, MD.

Sackville Street, October 31st, 1857.

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