=Infection and Disinfection=
Disinfection is the destruction of the infective power of infectious
material; or, in other words, disinfection is the destruction of the
agents of infection.
An infectious material is one contaminated with germs of infection.
The germs of infection are organic microoerganisms, vegetable and
animal--protozoa and bacteria.
The germs of infection once being lodged within the body cause certain
reactions producing specific pathological changes and a variety of
groups of symptoms which we know by the specific names of infectious
diseases, e. g., typhoid, typhus, etc.
Among the infectious diseases known to be due to specific germs are
the following: typhoid, typhus, relapsing fevers, cholera, diphtheria,
croup, tuberculosis, pneumonia, malaria, yellow fever, erysipelas,
_septicaemia_, anthrax, _tetanus_, gonorrhea, etc.; and among the
infectious diseases the germs of which have not as yet been discovered
are the following: scarlet fever, measles, smallpox, syphilis,
varicella, etc.
The part of the body and the organs in which the germs first find
their entrance, or which they specifically attack, vary with each
disease; thus, the mucous membranes, skin, internal organs,
secretions, and excretions are, severally, either portals of infection
or the places where the infection shows itself the most.
The agents carrying the germs of infection from one person to the
other may be the infected persons themselves, or anything which has
come in contact with their bodies and its secretions and excretions;
thus, the air, room, furniture, vessels, clothing, food and drink,
also insects and vermin, may all be carriers of infection.
=Sterilization= is the absolute destruction of _all_ organic life,
whether infectious or not; it is therefore _more_ than disinfection,
which destroys the germs of infection alone.
A =Disinfectant= is an agent which destroys germs of infection.
A =Germicide= is the same; an agent destroying germs.
An =Insecticide= is an agent capable of destroying insects; it is not
necessarily a disinfectant, nor is a disinfectant necessarily an
insecticide.
An =Antiseptic= is a substance which inhibits and stops the growth of
the bacteria of putrefaction and decomposition. A disinfectant is
therefore an antiseptic, but an antiseptic may not be a disinfectant.
A =Deodorant= is a substance which neutralizes or destroys the
unpleasant odors arising from matter undergoing putrefaction. A
deodorant is not necessarily a disinfectant, nor is every disinfectant
a deodorant.
The ideal disinfectant is one which, while capable of destroying the
germs of disease, does not injure the bodies and material upon which
the germs may be found; it must also be penetrating, harmless in
handling, inexpensive, and reliable. The ideal disinfectant has not as
yet been discovered.
For successful scientific disinfection it is necessary to know: (1)
the nature of the specific germs of the disease; (2) the methods and
agents of its spread and infection; (3) the places where the germs are
most likely to be found; (4) the action of each disinfectant upon the
germs; and (5) the best methods of applying the disinfectant to the
materials infected with germs of disease.
Disinfection is not a routine, uniform, unscientific process; a
disinfector must be conversant with the basic principles of
disinfection, must make a thorough study of the scientific part of the
subject, and moreover must be thoroughly imbued with the importance of
his work, upon which the checking of the further spread of disease
depends.
_Physical Disinfectants_
The physical disinfectants are sunlight, desiccation, and heat.
=Sunlight= is a good disinfectant provided the infected material or
germs are directly exposed to the rays of the sun. Bacteria are killed
within a short time, but spores need a long time, and some of them
resist the action of the sun for an indefinite period. The
disadvantages of sunlight as a disinfectant are its superficial
action, its variability and uncertainty, and its slow action upon most
germs of infection. Sunlight is a good adjunct to other methods of
disinfection; it is most valuable in tuberculosis, and should be used
wherever possible in conjunction with other physical or chemical
methods of disinfection.[20]
=Desiccation= is a good means of disinfection, but can be applied only
to very few objects; all bacteria need moisture for their existence
and multiplication, hence absolute dryness acts as a good germicide.
Meat and fish, certain cereals, and also fruit, when dried, become at
the same time disinfected.
_Heat_ is the best, most valuable, all-pervading, most available, and
cheapest disinfectant. The various ways in which heat may be used for
disinfection are burning, dry heat, boiling, and steam.
=Burning= is of course the best disinfectant, but it not only destroys
the germs in the infected materials, but the materials themselves; its
application is therefore limited to articles of little or no value,
and to rags, rubbish, and refuse.
=Dry Heat.=--All life is destroyed when exposed to a dry heat of 150 deg.
C. for one hour, although most of the bacteria of infection are killed
at a lower temperature and in shorter time. Dry heat is a good
disinfectant for objects that can stand the heat without injury, but
most objects, and especially textile fabrics, are injured by it.
=Boiling.=--Perhaps the best and most valuable disinfectant in
existence is boiling, because it is always at command, is applicable
to most materials and objects, is an absolutely safe sterilizer and
disinfectant, and needs very little if any preparation and apparatus
for its use. One half hour of boiling will destroy all life; and most
bacteria can be killed at even a lower temperature. Subjection to a
temperature of only 70 deg. C. for half an hour suffices to kill the germs
of cholera, tuberculosis, diphtheria, plague, etc. Boiling is
especially applicable to textile fabrics and small objects, and can
readily be done in the house where the infection exists, thus
obviating the necessity of conveying the infected objects elsewhere,
and perhaps for some distance, to be disinfected.
=Steam.=--Of all the physical disinfectants steam is the most valuable
because it is very penetrating, reliable, and rapid; it kills all
bacteria at once and all spores in a few minutes, and besides is
applicable to a great number and many kinds of materials and objects.
Steam is especially valuable for the disinfection of clothing,
bedding, carpets, textile fabrics, mattresses, etc. Steam can be used
in a small way, as well as in very large plants. The well-known
Arnold sterilizers, used for the sterilization of milk, etc., afford
an example of the use of steam in a small apparatus; while municipal
authorities usually construct very large steam disinfecting plants. A
steam disinfector is made of steel or of wrought iron, is usually
cylindrical in shape, and is covered with felt, asbestos, etc. The
disinfector has doors on one or both ends, and is fitted inside with
rails upon which a specially constructed car can be slid in through
one door and out through the other. The car is divided into several
compartments, in which the infected articles are placed; when thus
loaded it is run into the disinfector. The steam disinfectors may be
fitted with thermometers, vacuum formers, steam jackets, etc.
_Gaseous Chemical Disinfectants_
Physical disinfectants, however valuable and efficient, cannot be
employed in many places and for many materials infected with disease
germs, and therefore chemicals have been sought to be used wherever
physical disinfectants could not for one or more reasons be employed.
Chemicals are used as disinfectants either in gaseous form or in
solutions; the gaseous kinds are of especial value on account of their
penetrating qualities, and are employed for the disinfection of rooms,
holds of ships, etc. There are practically but two chemicals which are
used in gaseous disinfection, and these are sulphur dioxide and
formaldehyde.
=Sulphur Dioxide.=--Sulphur dioxide (SO2) is a good surface
disinfectant, and is very destructive to all animal life; it is one of
the best insecticides we have, but its germicidal qualities are rather
weak; it does not kill spores, and it penetrates only superficially.
The main disadvantages of sulphur dioxide as a disinfectant are: (1)
that it weakens textile fabrics; (2) blackens and bleaches all
vegetable coloring matter; (3) tarnishes metal; and (4) is very
injurious and dangerous to those handling it.
There are several methods of employing sulphur in the disinfection of
rooms and objects, e. g., the pot, candle, liquid, and furnace
methods.
In the pot methods crude sulphur, preferably ground, is used; it is
placed in an iron pot and ignited by the aid of alcohol, and in the
burning evolves the sulphur dioxide gas. About five pounds of sulphur
are to be used for every 1,000 cubic feet of space. As moisture plays
a very important part in developing the disinfecting properties of
sulphur dioxide, the anhydrous gas being inactive as a disinfectant,
it is advisable to place the pot in a large pan filled with water, so
that the evaporated water may render the gas active. For the purpose
of destroying all insects in a room an exposure of about two hours to
the gas are necessary, while for the destruction of bacteria an
exposure of at least fifteen to sixteen hours is required.
In the application of disinfection with sulphur dioxide, as with any
other gas, it must not be forgotten that gases very readily escape
through the many apertures, cracks, and openings in the room and
through the slits near doors and windows; and in order to confine the
gas in the room it is absolutely necessary to hermetically close all
such apertures, cracks, etc., before generating the gaseous
disinfectant. The closing of the openings, etc., is done by the
pasting over these strips of gummed paper, an important procedure
which must not be overlooked, and which must be carried out in a
conscientious manner.
When sulphur is used in candle form the expense is considerably
increased without any additional efficiency. When a solution of
sulphurous acid is employed, exposure of the liquid to the air
suffices to disengage the sulphur dioxide necessary for disinfection.
The quantity of the solution needed is double that of the crude drug,
i. e., ten pounds for every 1,000 cubic feet of room space.
=Formaldehyde.=--At present the tendency is to employ formaldehyde gas
instead of the sulphur so popular some time ago. The advantages of
formaldehyde over sulphur are: (1) its nonpoisonous nature; (2) it is
a very good germicide; (3) it has no injurious effect upon fabrics and
objects; (4) it does not change colors; and (5) it can be used for the
disinfection of rooms with the richest hangings, bric-a-brac, etc.,
without danger to these. Formaldehyde is evolved either from paraform
or from the liquid formalin; formerly it was also obtained by the
action of wood-alcohol vapor upon red-hot platinum.
Formaldehyde gas has not very great penetrating power; it is not an
insecticide, but kills bacteria in a very short time, and spores in an
hour or two.
Paraform (polymerized formaldehyde; trioxymethylene) is sold in
pastilles or in powder form, and when heated reverts again to
formaldehyde; it must not burn, for no gas is evolved when the heating
reaches the stage of burning. The lamps used for disinfection with
paraform are very simple in construction, but as the evolution of the
gas is very uncertain, this method is used only for small places, and
it demands two ounces of paraform for every 1,000 cubic feet of space,
with an exposure of twelve hours. Formaldehyde is also used in the
form of the liquid formalin either by spraying and sprinkling the
objects to be disinfected with the liquid, and then placing them in a
tightly covered box, so that they are disinfected by the evolution of
the gas, or by wetting sheets with a formalin solution and letting
them hang in the room to be disinfected.
The method most frequently employed is to generate the formaldehyde in
generators, retorts, and in the so-called autoclaves, and then to
force it through apertures into the room.
Of the other gaseous disinfectants used, hydrocyanic acid and chlorine
may be mentioned, although they are very rarely used because of their
irritating and poisonous character.
=Hydrocyanic Acid= is frequently used as an insecticide in ships,
mills, and greenhouses, but its germicidal power is weak.
=Chlorine= is a good germicide, but is very irritating, poisonous, and
dangerous to handle; it is evolved by the decomposition of chlorinated
lime with sulphuric acid. Chlorine gas is very injurious to objects,
materials, and colors, and its use is therefore very limited.
_Chemicals Used as Disinfectants_
Solution of chemicals, in order to be effective, must be used
generously, in concentrated form, for a prolonged time, and, if
possible, warm or hot. The strength of the solution must depend upon
the work to be performed and the materials used. The method of
applying the solution differs. It may consist in immersing and soaking
the infected object in the solution; or the solution may be applied as
a wash to surfaces, or used in the form of sprays, atomizers, etc. The
most important solutions of chemicals and the ones most frequently
employed are those of carbolic acid and bichloride of mercury.
=Carbolic Acid.=--In the strength of 1:15,000 carbolic acid prevents
decomposition; a strength of 1:1,000 is needed for the destruction of
bacteria, and a three per cent to five per cent solution for the
destruction of spores. Carbolic acid is used, as a rule, in two per
cent to five per cent solutions, and is a very good disinfectant for
washing floors, walls, ceilings, woodwork, small objects, etc. The
cresols, creolin, lysol, and other solutions of the cresols are more
germicidal than carbolic acid, and are sometimes used for the same
purposes.
=Bichloride of Mercury= (corrosive sublimate) is a potent poison and a
powerful germicide; in solutions of 1:15,000 it stops decomposition;
in solutions of 1:2,000 it kills bacteria in two hours; and in a
strength of 1:500 it acts very quickly as a germicide for all
bacteria, and even for spores. Corrosive sublimate dissolves in
sixteen parts of cold and three parts of boiling water, but for
disinfecting purposes it should be colored so that it may not be
inadvertently used for other purposes, as the normal solutions are
colorless and may accidentally be used internally. The action of the
bichloride is increased by heat.
=Formalin= is a forty per cent solution of formaldehyde gas, and its
uses and methods of employment have already been considered.
=Potassium Permanganate= is a good germicide, and weak solutions of it
are sufficient to kill some bacteria, but the objections against its
use are that solutions of potassium permanganate become inert and
decompose on coming in contact with any organic matter. Furthermore,
the chemical would be too expensive for disinfecting purposes.
=Ferrous Sulphate= (copperas) was formerly very extensively used for
disinfecting purposes, but is not so used at present, owing to the
fact that it has been learned that the germicidal power of this
material is very slight, and that its value depends mostly upon its
deodorizing power, for which reason it is used on excreta in privy
vaults, etc.
=Lime.=--When carbonate of lime is calcined the product is common
lime, which, upon being mixed with water, produces slaked lime; when
to the latter considerable water is added, the product is milk of
lime, and also whitewash. Whitewash is often used to disinfect walls
and ceilings of cellars as well as of rooms; milk of lime is used to
disinfect excreta in privy vaults, school sinks, etc. Whenever lime is
used for disinfecting excreta it should be used generously, and be
thoroughly mixed with the material to be disinfected.
_Disinfection of Rooms_
Practical disinfection is not a routine, uniform, and thoughtless
process, but demands the detailed, conscientious application of
scientific data gained by research and laboratory experiments.
Disinfection to be thorough and successful cannot be applied to all
objects, material, and diseases in like manner, but must be adjusted
to the needs of every case, and must be performed conscientiously.
Placing a sulphur candle in a room, spilling a quart of carbolic acid
or a couple of pounds of chlorinated lime upon the floors or objects,
may be regarded as disinfection by laymen, but in municipal
disinfection the disinfector must be thoroughly versed in the science
of disinfection and be prepared to apply its dictates to practice.
=Rooms.=--In the disinfection of rooms the disinfectant used varies
with the part of the room as well as with the character of the room.
When a gaseous disinfectant is to be used sulphur dioxide or
formaldehyde is employed, with the tendency lately to replace the
former by the latter. Wherever there are delicate furnishings,
tapestries, etc., sulphur cannot be used on account of its destructive
character; when sulphur is employed it is, as a rule, in the poorer
class of tenement houses where there is very little of value to be
injured by the gas, and where the sulphur is of additional value as an
insecticide. Whenever gaseous disinfectants are used the principal
work of the disinfector is in the closing up of the cracks, apertures,
holes, and all openings from the room to the outer air, as otherwise
the gaseous disinfectant will escape. The closing up of the open
spaces is accomplished usually by means of gummed-paper strips, which
are obtainable in rolls and need only to be moistened and applied to
the cracks, etc. Openings into chimneys, ventilators, transoms, and
the like must not be overlooked by the disinfector. After the openings
have already been closed up the disinfectant is applied and the
disinfector quickly leaves the room, being careful to close the door
behind him and to paste gummed paper over the door cracks. The room
must be left closed for at least twelve, or better, for twenty-four
hours, when it should be opened and well aired.
=Walls and Ceilings= of rooms should be disinfected by scrubbing with
a solution of corrosive sublimate or carbolic acid; and in cases of
tuberculosis and wherever there is fear of infection adhering to the
walls and ceilings, all paper, kalsomine, or paint should be scraped
off and new paper, kalsomine, or paint applied.
=Metal Furniture= should first be scrubbed and washed with hot
soapsuds, and then a solution of formalin, carbolic acid, or
bichloride applied to the surfaces and cracks.
=Wooden Bedsteads= should be washed with a disinfecting solution and
subjected to a gaseous disinfectant in order that all cracks and
openings be penetrated and all insects be destroyed.
=Bedding, Mattresses, Pillows, Quilts, etc.=, should be packed in
clean sheets moistened with a five per cent solution of formalin, and
then carted away to be thoroughly disinfected by steam in a special
apparatus.
=Sheets, Small Linen and Cotton Objects, Tablecloths, etc.=, should be
soaked in a carbolic-acid solution and then boiled.
=Rubbish, Rags, and Objects of Little Value= found in an infected room
are best burned.
=Glassware and Chinaware= should either be boiled or subjected to dry
heat.
=Carpets= should first be subjected to a gaseous disinfectant, and
then be wrapped in sheets wetted with formalin solution and sent to be
steamed. Spots and stains in carpets should be thoroughly washed
before being steamed, as the latter fixes the stains.
=Woolen Goods and Wool= are injured by being steamed, and hence may be
best disinfected by formalin solutions or by formaldehyde gas.
=Books= are very difficult to disinfect, especially such books as were
handled by the patient, on account of the difficulty of getting the
disinfectant to act on every page of the book. The only way to
disinfect books is to hang them up so that the leaves are all open,
and then to subject them to the action of formaldehyde gas for twelve
hours. Another method sometimes employed is to sprinkle a five per
cent solution of formalin on every other page of the book; but this is
rather a slow process.[21]
=Stables= need careful and thorough disinfection. All manure, hay,
feed, etc., should be collected, soaked in oil, and burned. The walls,
ceilings, and floors should then be washed with a strong disinfecting
solution applied with a hose; all cracks are to be carefully cleaned
and washed. The solution to be used is preferably lysol, creolin, or
carbolic acid. After this the whole premises should be fumigated with
sulphur or formaldehyde, and then the stable left open for a week to
be aired and dried, after which all surfaces should be freshly and
thickly kalsomined.
=Food= cannot be very well disinfected unless it can be subjected to
boiling. When this is impossible it should be burned.
=Cadavers= of infected persons ought to be cremated, but as this is
not always practicable, the next best way is to properly wash the
surface of the body with a formalin or other disinfecting solution,
and then to have the body embalmed, thus disinfecting it internally
and externally.
Disinfectors, coming often as they do in contact with infected
materials and persons, should know how to disinfect their own _persons
and clothing_. So far as clothing is concerned the rule should be that
those handling infected materials have a special uniform[22] which is
cleaned and disinfected after the day's work is done. The hands should
receive careful attention, as otherwise the disinfector may carry
infection to his home. The best method of disinfecting the hands is to
thoroughly wash and scrub them for five minutes with green soap,
brush, and water, then immerse first for one minute in alcohol, and
then in a hot 1:1,000 bichloride solution. The nails should be
carefully scrubbed and cleaned.
FOOTNOTES:
[20] Blankets, carpets, and rugs should be frequently hung out on the
line in the bright sunlight.--EDITOR.
[21] Unless books are valuable it is best to burn them. Paper will
hold germs for several weeks. Recent experiments show that certain
pathogenic bacteria, including the bacilli of diphtheria, will live
for twenty-eight days on paper money.--EDITOR.
[22] Duck, linen, or any washable material will do.--EDITOR.