During the epidemic the deaths in the several cities were:
| Population | Deaths | Deaths per 10,000 Inhabitants | |
| Hamburg | 640,000 | 8,605 | 134.4 |
| Altona | 143,000 | 328 | 23.0 |
| Wandsbeck | 20,000 | 43 | 22.0 |
That infectious matter was communicated to the Elbe water from Hamburg is not in any way a hypothesis. Cholera germs had been as a fact found in the Elbe water. They were found a little below the place where the Hamburg main sewer flows into the Elbe. They were also found in one of the two Altona basins into which the water flowed before filtration."
No more striking example could be found, demonstrating on a large scale the efficiency of filtration as a preventive of water-borne diseases than that of the cholera epidemic of Hamburg in 1892, yet, at the present writing, there are people holding public offices throughout the United States who do not believe in the value of filtration as a public prophylactic, or who are so indifferent as not to advocate its adoption. Nor is this disbelief confined to public officials; many there are outside of public office who have made no study of sanitation and cannot believe that merely passing water downward through sand will purify it, and for the benefit of those who wish to be better informed, the story of the Hamburg epidemic of cholera, together with the part played by filters in saving Altona from a worse visitation, cannot be too often told.
It is but natural that, suspicion having once fallen on water as a source or vehicle of disease, means would be adopted not only to properly sterilize water before delivering it to the public, but, furthermore, to select the source of supply where there was least danger of contamination from filth. By this time public water supplies had progressed to such a stage that but few towns, cities or villages of any importance were without a municipal plant. Further, most cities of any importance had a more or less complete system of sewers, and the filth from these sewers was discharging freely, and in the crude state, into the streams and rivers of the realm. Such a condition of affairs could not last long without causing a nuisance, as well as becoming a menace to the health of the commonwealth, and it was not long before the problem was discussed of purifying the sewage before discharging it into streams and rivers. In Great Britain, the pollution of streams was felt more keenly than in America. The population along the rivers in Great Britain is quite dense, and the rivers, which are comparatively small, are used as sources of supply for the different municipalities along the banks, so that some means had to be devised to prevent the people up stream from polluting and perhaps infecting it for those lower down. So early as 1840, this matter forced itself on the attention of Parliament, and in 1843, a royal commission, the Health of Towns Commission, was appointed to inquire into the present state of large towns and populous districts. This was followed in 1857 by the Sewage of Towns Commission, a royal commission appointed to inquire into the best means of distributing the sewage of towns, and in 1865 by the Rivers Pollution Commission, a royal commission appointed to inquire into the best means of preventing the pollution of rivers.
Progress was not at a standstill during this time, however, but, on the contrary, chemical precipitation of sewage and purification by the application to land were striving with each other for supremacy. Up to that time, the important part that bacteria play in the reduction of organic matter was not understood, and instead of affording every advantage for the decomposition and fermentation of organic matter under the least objectionable conditions, the principal efforts of those interested in the problem were to prevent or put off as long as possible the septic action of sewage. It was not until so late as the year 1880 that attention was turned toward the possibility of the micro-organisms in sewage. In that year Dr. Mueller took out a patent endeavoring to utilize the micro-organism in sewage for the purpose of purification. According to Dr. Mueller's views, "The contents of sewage are chiefly of organic origin, and in consequence of this an active process of decomposition takes place in sewage through which the organic matters are dissolved into mineral matters, or, in short, are mineralized, and thus become fit to serve as food for plants. To the superficial observer, however, it is chiefly a process of digestion, in which the various, mostly microscopically small, animal and vegetable organisms utilize the organically fixed power for their life purpose.
"The decomposition of sewage in its various stages is characterized by the appearance of enormous numbers of spirilla, then of vibrios (swarming spores) and, finally, of moulds. At this stage commences the reformation of organic substance with the appearance of chlorophyl-holding protococcus."
About the same time, December, 1881, the account of Mouras's automatic scavenger was published in France. Mouras had been working and experimenting along the same lines as Dr. Mueller, and the result was an apparatus consisting of a closed vessel or vault, with a water seal which rapidly changed excrementatious matter into a homogeneous fluid, only slightly turbid, and holding the solid matters in suspension in the form of scarcely visible filaments. The principle claimed for his automatic scavenger by Mouras was that animal dejecta within themselves contained all the principles of fermentation necessary to liquefy them.
The teachings of Dr. Mueller and Mouras went unheeded for a long time, on account of the chemical processes then in vogue. It was maintained by those who were supposed to know, that lime and other antiseptic substances were particularly valuable in sewage purification, because they destroyed living organisms, such as bacteria, which give rise to putrefaction and fermentation. They contended that if all the organisms could be destroyed, that sewage would be rendered unobjectionable. So conditions stood when in January, 1887, Mr. Dibden read a paper before the Institute of Civil Engineers, in which he pointed out that the very essence of sewage purification was not the destruction of bacterial life, but the resolution of organic matter into other combinations by the agency of the micro-organisms. He pointed out, further, that a septic and not an antiseptic action was what was wanted, consequently any process which arrested the activity of the bacteria was the reverse of what was desired. Dibden's paper had the effect of turning investigation in the right direction, but a world of experimenting on a practical scale would be necessary before the practice of sewage purification could be established on a safe, sound and scientific footing. It remained for the Massachusetts State Board of Health to conduct those investigations, and so thoroughly was it accomplished that the records of their experiments furnish the basis for sewage purification practice in the United States. The experiments have been carried on since 1887, and the thoroughness and value of these investigations can be judged by the fact that during one period of twenty-two months four thousand chemical examinations were made in addition to the microscopic examinations.