Fig. 77.—Spring infected by polluted ditch.
Another example of the way in which underground waters, such as springs, may become contaminated is described by Whipple as occurring at Mount Savage, Maryland, in 1904. Through this village ran a small stream known as Jennings Run, which was grossly contaminated with fecal matter. In July, 1904, a woman who had nursed a typhoid patient in another town came home to Mount Savage, ill with the disease. She lived in a cottage on the hillside above the stream, and the drainage of the cottage was conveyed through an iron pipe onto the ground just above the stream. Figure 77 (after Whipple) shows the relative positions of the cottage and stream. Heavy rains occurred during the first week in July which probably washed the infectious matter from the ground into the ditch and then through the ground into a spring just below down the slope. A week afterwards twenty workmen who had been drinking water from the spring came down with the fever and new cases occurred daily for a week or two.
An interesting epidemic occurred in Massachusetts, caused by a farmer's boots carrying infectious matter from recently manured fields onto the well cover, whence it was washed into the well by repeated pumping.
The moral of these incidents is very plain, namely, that where any possibility of the infection of drinking water occurs, that water ought either to be avoided or else to be thoroughly sterilized before using. This applies particularly to the old-fashioned well,—the kind with loose board covers and chain pumps.
Construction of wells in reference to typhoid.
Two points already mentioned are essential if well water is to be kept pure. One is to line the well with a water-tight masonry lining, and the other point is to have the cover of the well made with a thoroughly water-tight coating. This does not always give full protection, since in some cases polluting matter may pass through even ten feet of soil. This would be particularly true if the well was in a fissured or seamed rock, and very recently the writer found a well dug in a laminated granite, where a near-by sewer, leaking at the joints, contaminated the water of the well, although the well was cased with an iron casing twenty-five feet deep. The sewage escaped into a crack in the rock and followed the crack down vertically and horizontally into the well. Limestone is even more dangerous if any pollution exists in the vicinity. In cases where a well goes down to a horizontal layer of limestone and where a privy vault is dug to the same rock, it is found that pollution will follow the surface of the rock horizontally a long distance, and this condition of things always makes a well water suspicious. In sand or fine gravel, on the other hand, the danger of contamination is almost negligible; on Long Island, for example, the cesspools and well are both dug ten or fifteen feet deep and only fifty feet apart without any trace of contamination being detected.
Milk infection by typhoid.
Milk is responsible for perhaps 5 per cent of the cases of infection. Although the infection is always foreign to the milk itself,—that is, enters the milk only after the milk is drawn from the cow,—milk frequently becomes infected because infected water has been added to it or because the cans have been washed in infected water, or because some persons in contact with a typhoid patient have had their hands infected and then handled the milk or the milk utensils. There are a number of epidemics which have been clearly traced to milk polluted in one of these ways. In Somerville, Massachusetts, for example, in 1892, 32 cases occurred, 30 of which were on the route of a single milkman. It was found that the milkman had two sons, one of whom had typhoid fever just before the outbreak. This son washed the milk cans and mixed the milk in a milk house in the city, and the inference was that in some way this man infected the milk, probably in one of the mixing cans.
In Stamford, Connecticut, in 1895, an epidemic occurred which caused 386 cases and 22 deaths. Ninety-five per cent of all the cases occurred among those who took milk from one dealer, and it was probable that in this case the infection came from using a badly polluted water to wash the cans. In Montclair, in 1902, a small epidemic involving 28 cases occurred, where the health officers decided, after having found out that the cases were all among those customers taking milk in pint bottles, that the infection came from a house on the route, where typhoid fever had occurred. It appeared that this family infected the bottles left at their house, and since the milkman failed to sterilize the bottles before re-filling them, the infection was passed on to others also taking milk in pint bottles.