absorption into the circulation, by producing fever, paralysis of particular parts, and sometimes death. <Callout type="important" title="Important">Diphtheria is primarily a throat disease, spread via sputum and objects like books or handkerchiefs.</Callout> 9. How Diphtheria is spread. — Inasmuch as diphtheria is a disease of the throat especially, it is easy to see that it must be chiefly conveyed from one person to another by sputum and by objects which come in contact with the mouth or lips. Kissing and fondling among children, or parents and children ; fingers, which, especially in children, are too often in the mouth; books, handkerchiefs, pencils, playthings, and food bitten and passed from hand to hand, —all these may be vehicles of contagion and infection in this microbic disease. It may be spread by dried sputum <Callout type="warning" title="Warning">Dried sputum can remain infectious for days.</Callout> On the left, as they appear under the microscope in discharges from the throat of a diphtheritic patient. On the right, after cultivation in the bacteriological laboratory in dust, by milk infected by milkers suffering with the disease, by infected food, and possibly by pets, such as cats and dogs and even birds, suffering from the disease. 10. The Prevention of Diphtheria. — Diphtheria being primarily a disease of the throat, and therefore distributed both by personal contact and by spittle, it would seem to suffice for its prevention to isolate patients having the dis- ease as long as they are capable of communicating it to others, and thus cut off the escape and distribution of the germs. Unfortunately, however, in this, as in many other infectious diseases, persons often have the disease for some time before they or their friends discover the fact; and some mild cases of this malady (as also of typhoid fever and other infectious diseases) probably occur and run their course without ever having revealed their true character. Hence arises the difficulty of accounting for the origin of some apparently inexplicable cases, and also the difficulty of stamping out a disease of this kind. Diphtheria is not an eruptive disease, and ought, therefore, to be more readily controlled than smallpox, scarlet fever, or measles, which are doubtless most often disseminated by means of scales shed off from the skin during the “peeling” which follows the eruption. It should be clearly understood that all kissing by persons having sore throats, or the mouthing of pencils or other objects by children, is a dangerous practice; and that fingers, which so readily find their way into mouths, may as easily as not carry infection to books, playthings, food, letters, or other objects which are “handled.” Letters sealed or handled by diphtheritic patients, or by persons attending them, have probably at times conveyed the germs of disease to persons at a distance in whom the appearance of the illness seemed quite unaccountable. Here also, as in tuberculosis, care in the disposal of sputum is of great importance. - Within a decade the discovery of an antitoxic serum, antitozin (see p. 499), has given us a novel and invaluable means of defense against the microbes of diphtheria by increasing the resistance of the human body so that it shall be no longer susceptible to the disease. But as this discovery means much more to hygiene than the control of this one disease, we shall devote to its careful consideration an entire paragraph beyond. 11. The Spitting Nuisance, as the habit of public spitting is often called, is not only a disgusting nuisance but a real menace to the public health, because, as will now readily be seen, it may be the means ‘of spreading abroad diseases, such as tuberculosis and diphtheria, with which many persons — incipient cases, or “walking” cases—may be moving about. Fortunately, the habit is chiefly confined to one sex, and this fact shows how easily it might be controlled if custom demanded. 12. Malarial Fever, or ‘‘Malaria,”’ is a world-famous disease, especially common in warm climates but also frequently occurring in the more temperate zones. It is probably by far the most important of all tropical diseases, for while it does not kill as do yellow fever and Asiatic cholera, it is much more common and disables a far greater number of victims. Malaria has long been associated in the popular mind with low grounds and swamps. Experience has shown, however, that it cannot be caused by swamps alone, for many swamps and marshes are entirely free from malaria. Sometimes it has seemed to go with the digging up of earth; yet the earth has very often been opened and thrown about without causing any malaria whatever. The true source of this disease remained an absolute mystery until, in 1880, Laveran, a French investigator resident in Algiers, discovered in the blood of malarial patients a microbe of a very peculiar kind, —not a bac- terium, nor even a plant, like the microbes of tuberculosis, typhoid fever, and diphtheria, but an animal known as a hematozoén, or sporozoén, belonging among the simplest animals, or protozoa (see p. 469). Figure 126 gives illustrations of some of the various forms of the microbe, and its life history is outlined in the description of the figure. But even after the microbe of malaria had been detected no one knew, for ten years longer, whence it came, or whether it lived outside of man at all, or, if not, how it was conveyed from victim to victim. When, at last, in 1899, as if for a final benediction upon mankind by a century wonderfully rich in human and especially in medical progress, the whole subject was cleared up, the solution of the riddle was found to be as simple as it was unexpected, for the <Callout type="important" title="Important">Malaria is spread by mosquitoes, specifically female Anopheles.</Callout> Fic. 126. The malaria microbe (Plasmodium malarie) and a malarial mosquito. After Leuckart-Chun’s wall diagram 1, the microbe; 2-5, its growth in a red blood corpuscle; 6, its multiplication and escape from the corpuscle (it is now ready to infect fresh blood cor- puscles) ; 7, 8, crescentic forms of the microbe. For further development the microbe must be transferred from man to mosquito (by a biting, i.e. bloodsucking, mosquito). In the stomach cavity of Anopheles: 9, female stage of the microbe; 9a, 9b, male stage; 10, union of 9 with one of the vibratile arms of 90; 11, the microbe resulting from 10. ? In the body proper of Anopheles: 12, The microbe (11) has penetrated the stomach wall of the mosquito and embedded itself on the outer (body) side of the stomach. Here it undergoes a process of growth, cell division, and multiplication (13), eventually forming ‘‘ tumors”? on the outside (body side) of the mosquito’s stomach, as shown in 15. From these tumors the microbes escape into the body cavity of the mosquito and find their way into the salivary glands (shown in section in 16). From these they are readily trans- ferred (with the saliva) into a human body bitten by Anopheles. 14, female malarial mosquito (head of male below). the blood of a man having <Callout type="important" title="Important">Malaria is spread primarily through bites from infected female Anopheles mosquitoes.</Callout> MICROBIC DISEASES. PREVENTION 491 vehicle proved to be a common insect, a special mosquito, long known as a pest, but never hitherto suspected or dreaded as a bearer of disease. At once it became clear why malaria is a disease of some warm climates and some seasons, and why it “hangs about” some swamps and not about others. 13. How Malaria is spread. — The malarial microbe is _ a microparasite (p. 467), spending a part of its life in man and a part in certain mos- quitoes, which are thus its “hosts.” A mosquito of the right kind bites and sucks malaria, and having thus become infected bites other persons, injecting into them germs of malaria, along with that poison which causes the familiar swelling often fol- lowing a mosquito bite. It is important to note that only one genus of mosquito <Callout type="important" title="Important">Only female Anopheles mosquitoes can spread malaria.</Callout> Fic. 127. Anopheles punctipennis (Anopheles), and that not the (female). After a photograph commonest in most places, from life by W. Lyman Under- wood seems capable of conveying the disease. Moreover, it is only the female Anopheles —and even that only after it has become infected by biting a person having the disease — which can transmit malaria. Hence many mosquitoes, even if Anopheles, are harmless, as are all mosquitoes in regions in which no Anopheles or no “malarial microbes exist. For the causation of malaria three things are re- quired, namely, (a) malarial microbes, (6) female Anopheles, and (c) susceptible victims. Fortunately the first two do not always coexist, and in case either is missing malaria Common in the northern United States 492 THE HUMAN MECHANISM is absent. Many places abounding in mosquitoes have no malaria, either because there are no Anopheles, or be- cause the Anopheles pres- ent have never become in- fected. 14. The Prevention of Malaria. — Beyond a gen- eral reénforcement of the body by wholesome living, the only means yet known of avoiding this disease is the avoidance of mosqui- Fic. 128. The malaria mosquito(Anoph- which they abound, and in eles) above, and the common mos- Which malaria also occurs. quito (Culex) below. After photo- ; ; graphs from life by W. Lyman Un- If a region contains no derwood malaria, the mosquitoes in - Showing a characteristic difference in the it cannot produce the dis- pe oes ease. If the region is ma- larious but has no malarial mosquitoes, no fresh cases, so far as known, can occur. But if malarial fever and malarial mosquitoes coexist, then the only hope is to remove one or the other, and if possible both. For relief from malaria already fastened upon a patient, application should be made to a physician. For the extermination of mosquitoes from a neighborhood, all swamps and marshes must be drained, and pools of stagnant water either treated with crude petro- leum or stocked with fishes that will feed upon and destroy the mosquito larve.t 15. Yellow Fever is an infection greatly dreaded in the tropics. It is now attributed to a microbe somewhat similar 1 For further information on this subject see Dr. L. O. Howard, Mos- quitoes, How they live, How they carry Disease, etc., New York (McClure), 1901; W. L. Underwood, Mosquitoes and their Extermination, Boston (W. B. Clarke), 1903; Celli, Malaria according to the New Researches, New York (Longmans), 1900. toes in those regions in » Same formerly the disease was frequently MICROBIC DISEASES. PREVENTION 493 to that of malaria, and which is believed to be conveyed, like the malarial microbe, by a mosquito, though of another kind, Stegomyia by name. If this view is correct, yellow fever is to be prevented only by avoiding these mosquitoes. Havana, which was formerly cursed by yellow fever, has been virtually freed from it by preventive action based wholly on the mosquito theory of its causa- tion ; and the suppression of yellow fever in Cuban ports, from which exported to the United States, means much to the southern states of the Union. In 1905 a disastrous outbreak Pee eT aioe fave: of yellow fever occurred in New mosquito (Stegomyia). Orleans and vicinity. Its germs After a drawing by L. O. were probably brought in from Howard some infected district nearer the tropics by mosquitoes (Stegomyia) on ships and on fruit (bunches of bananas). The epidemic was fought wholly upon the mosquito theory, and with results entirely satisfactory to the sanitarians in charge. 16. Some Other Infectious or Contagious Diseases, and how they are supposed to be spread. — In the case of some of the commonest infectious or contagious diseases we are still in the dark both as to their precise causation and the ways in which they are scattered abroad. Concern- ing measles, chicken pox, and whooping cough, for exam- ple, we are still awaiting such discoveries as have already been made for tuberculosis and the other diseases described above. We have also referred above (p. 380) to the fact that some colds or influenzas appear to be infectious. Attempts have been made to detect the microbes of the “grippe” 494 THE HUMAN MECHANISM and other influenzas, and figures are often given of germs found associated with disorders of this class. Figure 130 is an example of this kind, although it is not safe to say positively that the microbes chiefly concerned have really been as yet identified. But while we patiently wait for more light, we have good reason, because of their general character, to believe that these also are microbic diseases, caused likewise by microparasites transmitted either directly or indirectly from victim to victim. Experience has shown that the same kind of effort which tends to prevent diseases undoubtedly microbic tends to prevent these also; so that at present, and for all practical purposes, we may consider that we know enough about their causation and spreading to enable us to deal with them intelligently, fearlessly, and hopefully. 17. Scarlet Fever, Measles, and Chicken Pox belong to the group of eruptive diseases, a term derived from the fact that persons having any of them are usually, sooner or later, “broken out,” or more or less covered with an erup- tion, or rash. When this eruption heals, scales of the skin are shed off, and the wide dissemination of these scales during the process of “peeling” is believed to be one rea- son why eruptive diseases are more contagious than some microbic diseases (like tuberculosis and diphtheria) which are not eruptive. Persons suffering from an eruptive dis- ease should not be allowed to go about among other people until they have ceased peeling. As for the prevention of measles, chicken pox, scar- let fever, and whooping cough, the only means at hand at present seem to be isolation and non-intercourse. To maintain or increase the resistance of the body no better means are known than good feeding, temperate living, and, in general, a wise and wholesome conduct of life ; yet even so, immunity is often purchased only at the cost of one or more attacks, and prevention by isolation is frequently difficult under the conditions of modern life, especially in tenements and crowded districts. 18. Summer Complaint in Children is a severe and often dangerous summer diarrhea, believed to be caused by microbes and apparently due in part to wrong feeding. In cities it appears to be closely connected with the use of stale milk, and is often prevented or overcome by using very fresh milk, or even by pasteurizing ordinary milk (p- 475). This is readily done by immersing bottles of milk in water and then heating the water to a temperature of about 160° F. for five minutes. If no thermom- eter is available, it will suffice to bring the milk nearly (but not quite) to the boiling point and hold it at that temperature for a few minutes. 19. Smallpox, a disease once so common that “scarce one in a thousand” escaped it, is now happily rare in most highly civilized countries. It is an eruptive fever, small pustules or pocks giving it its name, and while not as fatal as some of the diseases shortly to be consid- ered, it is peculiarly loathsome and very apt to leave after it lifelong disfigurement, or pitting. It is hard to realize to-day the dread and fear with which our ancestors rightly regarded smallpox, and for this reason some people make much more of the slight discomfort and insignificant dan- ger of vaccination than of the loathsome smallpox itself; but if communities ever cease to take the simple but in- dispensable steps required to prevent smallpox, outbreaks of the disease will undoubtedly remind them in alarming fashion of what they had previously escaped. It is not yet absolutely proved, although it is now gener- ally believed, that smallpox is caused by microbic activity ; but it is certain that it is extremely contagious, probably through the scales cast off from the skin of those suffer- ing from it, with which scales the specific microbes are blown or handed about. Experience has shown that great gain results from “ iso- lating” or “ quarantining” smallpox patients in a deten- tion hospital (to which the name of “pesthouse” was formerly given). Smallpox patients are thus removed and isolated, while those suffering from typhoid fever or con- sumption are not, partly because of the much greater con- tagiousness of smallpox, and partly because of its graver and more loathsome character. In smallpox, as in other diseases, wholesome living diminishes the danger of infection; but it is a matter of history that in the days when the disease was prevalent and the question was put to the severest test, general good health proved an unreliable defense. Fortunately, however, the human race, which was once so frightfully scourged by this disease, has discovered a more certain means of protection, which consists not in the warding off or destruction of microbes but in an enhancement of the powers of resistance of the organism, so remarkable as even to constitute for extended periods virtual exemption, or immunity, from smallpox. The methods by which this extraordinary result is reached are known as inoculation and vaccination. 20. Immunity. — The best of all defenses against any disease would be complete insusceptibility, or immunity, to it; for no matter how ingenious, elaborate, or com- plete the devices may be for preventing disease germs from finding access to the body, accidents may always happen which
Key Takeaways
- Diphtheria is primarily spread through sputum and objects like books or handkerchiefs.
- Malaria is spread by mosquitoes, specifically female Anopheles.
- Isolating patients with infectious diseases can help prevent their spread.
- Good hygiene practices are crucial in preventing the spread of microbic diseases.
Practical Tips
- Regularly clean and disinfect commonly touched surfaces to reduce the risk of spreading diphtheria or other microbic diseases.
- Use mosquito nets and repellents when traveling to areas with a high risk of malaria.
- Properly dispose of sputum by wrapping it in tissue and disposing of it in a sealed container.
Warnings & Risks
- Public spitting can spread diseases like tuberculosis and diphtheria, so avoid this habit.
- Only female Anopheles mosquitoes can transmit malaria; thus, eliminating these mosquitoes is crucial for prevention.
- Isolating patients with infectious diseases may be difficult in crowded living conditions.
Modern Application
While the specific methods of preventing microbic diseases like diphtheria and malaria have evolved significantly since 1907, the principles of isolation, hygiene, and public health remain crucial. Modern techniques such as vaccines and antibiotics offer more effective prevention and treatment options but underscore the importance of understanding these foundational concepts for any survival situation.
Frequently Asked Questions
Q: How does diphtheria spread?
Diphtheria spreads through sputum, saliva, or other respiratory secretions. It can also be transmitted by objects like books, handkerchiefs, and toys that come into contact with an infected person's mouth or nose.
Q: What are the symptoms of malaria?
Malaria causes fever, chills, sweating, headache, muscle aches, nausea, and vomiting. Severe cases can lead to complications like organ failure, seizures, and death.
Q: How can one prevent the spread of diphtheria in their community?
Isolate infected individuals, clean and disinfect surfaces regularly, avoid public spitting, and encourage good hygiene practices among children. Vaccination is also crucial for long-term prevention.