Direct Quoted: FM 21-10

Communicable Diseases: 
Cases and suspects should be separated from other troops and every precaution taken to prevent transmitting the disease. Carriers may not require isolation but should have their activities restricted to the extent the medical officer believes necessary... Control of transmitting agents includes the following general measures which should be enforced at all times:
(1) Prevention of overcrowding.
(2) Correct ventilation of barracks and tents.
(3) Purification of water.
(4) Careful selection and preparation of food.
(5) Good sanitation of messes.
(6) Effective disposal of waste.
(7) Control of disease-bearing insects.
(8) Personal cleanliness.

Respiratory diseases are the greatest causes of sickness in the Army. They exact the greatest toll during winter and spring and are most common among newly inducted troops. These diseases are spread by secretions from the mouth and nose and usually are transmitted through close association with infected persons.

The principal intestinal diseases are common diarrhea, bacterial food poisoning, bacillary dysentery, amebic dysentery, paratyphoid fever, typhoid. fever, helminth infections (worms), and cholera. They are sometimes called 'filth' diseases since they are caused by food or water contaminated by human excretions. Food may be contaminated by infected food handlers who are careless or dirty in their personal habits or by the housefly which carries germs directly from the latrine to the mess hall or kitchen. Again, organisms may be carried directly to the mouth by soiled fingers. The usual means of transmission of these diseases are often expressed as 'feces, fingers, flies, and food'.... The most effective means of cutting down intestinal diseases is the control of the agencies which transmit them--human waste, flies, food, and water.... However, since there is not practical means of building up immunity against the other intestinal diseases, close attention must be paid to the following measures:
(1) Mess sanitation, including careful selection and supervision of food handlers.
(2) Waste disposal.
(3) Fly control.
(4) Personal cleanliness, paying particular attention to the washing of hands immediately after visiting the latrine.
(5) Careful selection, inspection, and protection of food supplies.
(6) Purification and protection of water supply.
(7) Avoidance of unauthorized water and food sources.
(8) Rigid sanitary discipline.

Venereal Diseases:
Venereal disease (VD) control is the responsibility of the unit commander, who must initiate and maintain the VD control program. The Medical Department supplies him with information and advice as to suitable control measures. The individual soldier, in turn, is responsible for carrying out measures designed to protect his own health and in turn that of his unit. The venereal disease rate of a unit therefore is a fair index of its discipline, training, and administration.

The number of cases of venereal disease in any unit depends on two factors:
(1) The number of sex contacts with infected women.
(2) The number of these exposures that are unprotected by adequate prophylaxis.

The VD rate can be cut down effectively by carrying out the following measures:

a. Reduce sex exposures. The only completely satisfactory way to prevent venereal disease is to avoid promiscuous sexual intercourse altogether. Avoidance of sex relations is not harmful to the soldier's health or well-being. The fact cannot be overlooked, however, that in any unit there will be some men who will have promiscuous sex relations. The degree of promiscuity that is carried on will depend to a large extent on the backgrounds of the men in the unit, and on the particular Army environment in which they find themselves. It is, of course, impossible to do anything to change the backgrounds of the men, but it is possible to do something about the environment. The following measures will help to reduce the number of sex exposures:
(1) Provision of substitute activities on the post, such as athletics and wholesome recreation of other kinds. These will catch the attention and interest of the men, and help to occupy off-duty time.
(2) Limitation of the activities of professional prostitutes and pick-ups. Commanding officers can do much in this respect by working with the civilian authorities.
(3) Declaring houses of prostitution and establishments which serve as places of pick-up or exposure "off limits."

b. Increasing the use of prophylaxis.
(1) Mechanical prophylaxis. The condom or rubber offers considerable protection against infection if used properly.
(2) Chemical prophylaxis. This helps to destroy germs after they have been transferred from one person to another.

c. Reduction in sources of infection. Ordinarily the sources of infection are not under military control. Therefore, the problem of reducing their number is primarily a function for civilian health and law enforcement authorities.

Field Water Supplies:
Impure water may serve as a means for the transmission of various diseases, including dysentery, diarrhea, cholera, schistosomiasis, and typhoid fever. Water from streams, shallow wells, ponds, swamps, and lakes is especially likely to carry such disease organisms. All water supplies should therefore be treated with sufficient chlorine to kill all disease organisms, and troops should be trained not to drink unchlorinated water. 

Climate, types of work, and. general camp conditions regulate the amount of water men need. In permanent stations, the average requirement per man is 70 gallons a day, though in semipermanent camps, it varies from 20 to 40 gallons. The quantity used in the field is generally much less, but this depends on availability and restrictions. Men in the field cannot be kept in good health with less than I gallon a man, each day, for drinking and cooking.

When water is distributed to temporary camps by truck, 5 gallons for each man will take care of daily cooking, drinking, and washing. Animals need 10 gallons a day. Troops on the march or on bivouac need 2 gallons a day. Under average conditions of combat, men can get along for as long as 3 days with 11/2 to 2 quarts a day. Animals in combat zones require 3 to 5 gallons.

A fully equipped soldier expends 90 calories or heat units for every mile of march, and requires 180 cc of water to dissipate as heat. For 2/2 miles or 1 hour, his system needs 450 cc of water, or a fraction under 1 pint. In 2 hours, a soldier can lose a quart of water through evaporation. There are too many variations of heat and energy to standardize water intake, but one simple rule should be useful: when water is plentiful men should drink when thirsty-and drink enough to satisfy their thrist.

Mess Sanitation: 
No part of the soldier's everyday life is more important than a good mess. Good food can contribute much to morale and efficiency but clean food is absolutely necessary for the Army's health. Contaminated or infected food is the main cause of intestinal diseases. 

Mess sanitation calls for constant vigilance over the food supply, in cleanliness, in cooking, and in refrigeration. Other important features discussed later in this chapter include supervision of food handlers, kitchen cleanliness, care of equipment, and control of insects and rodents....

When necessary, soldiers in the field must wash and retain their own mess kits. Just before each meal the mess kits are disinfected as described in a below. After the meal, remaining food is scraped off as completely as possible into a garbage can or pit, using the spoon. The washing, rinsing, and disinfection after use is done in a series of three containers (usually GI cans) by the method described in b below: 

Before each meal, the mess gear with the exception of the canteen will be disinfected by immersing for not less than 3 seconds in clear boiling water. All of this equipment including cutlery may be assembled by hanging it on the meat can. Wire hooks or other suitable holders may be improvised to avoid too close contact with the steam.

Washing, rinsing and disinfection after use:
(1) Wash thoroughly in first container, filled with hot soapy water (120 ° F. to 1400 F.) or other approved detergent solution. A long-handled brush is used for washing.
(2) Rinse by dipping several times in second container, filled with clear boiling water.
(3) Disinfect by immersing for not less than 3 seconds in the third container filled with clear boiling water.
(4) Air-dry after shaking off excess water.

Personal Hygiene:
Before a man is accepted into the Army, he is given a thorough physical checkup to see that he has no disease. After that, it is his duty to keep himself in the best possible physical condition and to protect himself from infections. Thecare which a person gives his body to keep in good health is called personal hygiene.

Every man has some degree of natural resistance to infection. This resistance can be increased by any measures which protect or improve his general health; for example--
a. Keeping the face, body, hands, and feet dean.
b. Protection from cold and chilling with the help of suitable clothing, blankets, and housing.
c. Enough of the right kind and variety of food.
d. Physical training, including athletics.
e. At least 7 to 8 hours sleep each day, preferably continuous.
f. Prevention of undue fatigue. (This is particularly important in training camps where there are epidemics of respiratory diseases.)
g. Healthful recreation. (Morale of an organization is closely related to the physical condition of its men.)