"A treatise on pneumonic plague"

Wu Lien-teh, who lead efforts against the plague of 1910-11 in Manchuria and developed the first modern medical mask, published a history of the mask and results of his own design in 1926. You can download the book from us (118.6 megabytes).

We have included the author's footnotes but not references.

History of the Mask

Before discussing the measures as practised to-day, we may dwell shortly upon the various means adopted for personal prophylaxis as practised in the past. History takes us back to the time of the Black Death, when medical experts were apparently aware that, in the pneumonic type of plague, the infection was directly transmitted through the air (158). This seems highly advanced by the side of the practices adopted in later centuries, such as in Milan (1630), Rome (1656), etc., when the mask and other prophylactic implements were used without any clear idea of the respiratory mode of infection beyond a vague hypothesis of some "miasma" being present (159).

The oldest record describing measures of prophylaxis against pneumonic plague can be traced to the year 1348 (160): A doctor at Montpellier, in a treatise on the epidemic, exhorts the people to beware of the breath of patients and advises them to hold a sponge moistened with vinegar before the nose when near the sufferers. Strange to say, he applies this last measure in warm weather; in cold weather he advises the inhalation of certain spices. Ibnul Khatib (161), an Arab, advocated similar precautions at the same time. Of interest also were the words of Bishop Kanutus, Professor of Medicine at Montpellier in 1382 (162): "Doctors and attendants must keep away from the patients and turn their faces towards the window". This learned divine added that he personally held a sponge moistened with vinegar before his mouth and nose, and confessed that it was this precaution which, contrary to the apprehensions of his friends, kept him well throughout those trying times.

In the sixteenth century, the characteristic anti-plague costume came into vogue, consisting of a mask with a beak, in which were placed spices, and of garments of leather or oilcloth. The mask of later years was also equipped with eyeglasses of crystal. Sometimes the physicians walked on stilts when visiting their patients or rode on horseback. Thus Sticker, who collected many references on the use of this costume (163), says that Dr. Lardoni, the quarantine inspector at Alexandria, always rode on horseback when leaving his house; both he and his horse were covered with oilcloth from head to foot. In spite of these and other precautions, Lardoni contracted plague and died in 1835 (164). Sticker records also that, according to the French quarantine regulations which were still valid at that time, the medical men were not permitted to come nearer than twelve meters to the patients (165); they even looked at sufferers through a hand telescope.

Of fascinating reading are the measures evolved by the lamas and the population in Mongolia, which are in some respects quite similar to those adopted in medieval Europe.

As just mentioned, the famous plague costume of former centuries was still prevalent in the nineteenth century. When we consider that these precautions were advocated on account of the vague theory of "contagion", we cannot help admiring the more lucid conceptions held at the time of the Black Death and must admit that, after five centuries, little or no progress had been made in this respect.

As far as we can ascertain, no use was made of masks during the Vetlianka outbreak, the doctors taking such precautions as oiling their hands and spraying carbolic solution (166). Probably, when dealing with pneumonic cases, no precautions were then taken, since their plague character was realised by a few advanced thinkers only. We can gather that the high mortality among the staff was principally due to this ignorance of their infectious nature (167). Soon after the outbreak, an elaborate mask was recommended by Dogel (168), and a complete anti.plague costume of gutta-percha was designed by Pashutin (169). Dogel points out that Naegeli (170) had recommended the use of a respirator for certain other infectious diseases, as diphtheria and cholera. We reproduce two illustrations showing the equipments recommended by these Russian physicians. Pashutin's costume particularly is worthy of the imagination of a Jules Verne.

The first available modern reference to measures of personal prophylaxis against lung plague is contained in the German Plague Report (171), where the Commissioners advocate the use of a moist sponge to be tied before the nose and mouth and to be disinfected after use. Actually the principle is the same as that recommended more than five centuries ago by Kanutus. A curious freak of fate lies in the fact that Sticker, one of the members of the German Commission, afterwards ridiculed the use of masks (172). Much as we must admire Sticker's campaign against the fads of the "contagionists", he certainly erred when he did not differentiate between the measures against bubonic plague on the one hand and pneumonic plague on the other.

Almost simultaneously with the German Commission, the use of masks was recommended by the Japanese authorities in the following order (173):

"In any case suspected to be plague, with cough and dyspnea, the face of the patient should, during examination or transfer, be covered by a cloth or, better, by sublimate cotton, and the physician and all attendants should, as soon as the nature of the case is suspected, cover their mouths and noses with a flat sponge, not less than four inches in diameter, which has been wrung out of 1:1,000 sublimate solution; and this must be retained over the mouth and nose until the work is finished. This applies equally to all engaged in cleaning and disinfecting the house after the patient's removal."

It can be seen that this excellent instruction mentions almost all the advantages of the protective mask, and wisely includes within its grasp all suspicious respiratory as well as pneumonic cases.

The use of masks was also prescribed in other plague regulations issued early in the present pandemic, e.g., the Belgian instructions (174), which note that "nurses must avoid leaning over his (the patient's) face and being unnecessarily close to him. They should hold before the mouth and nose a plug of cotton wool whenever they approach the patient; or, better still, envelop the head in a fine muslin or tulle". Bruce Low adds that "a light veil of this kind, a sort of mask, is also recommended for patients, to protect those around them from the danger of infected sputum and saliva". This last-named precaution was utilised by Gotschlich in Alexandria (175).

In the early years of the present pandemic, the mask was used in some outbreaks. Eckert (176), who observed an outbreak at Newchwang in 1903, said: "In order to reduce the danger for the personnel, which is specially great when nursing pneumonic-plague patients, masks were prepared according to a model seen by the author in Japan. In the region of the eyes these masks have a gauze veil, to be replaced later on by a sheet of mica. The mask is connected with the gown and helps to protect the conjunctiva and the mucous membranes of nose, mouth and tonsils."

The Mask as at present used.

From the above historical sketch it may be gathered that the use of protective masks against plague dates back for many centuries. At the Mukden Conference, a simplified variety, which had been success. fully used by the Chinese staff at Harbin in 1911, was definitely recommended. Different models were worn during the first Manchurian epidemic, many having a stiff or metallic frame. Only one kind of mask, at once simple and inexpensive, yet apparently efficient, introduced by Wu Lien-Teh, was universally adopted (177). This consists of two layers of gauze enclosing a flat oblong piece of absorbent cotton 6 inches by 4 inches. It can be easily made by cutting the usual surgical gauze (9 inches wide), as supplied from the shops, into strips, each measuring 3 feet in length. Each strip is then doubled lengthwise so as to contain in the middle a flat piece of cotton wool measuring 4 inches by 6 inches. At either end of the gauze two cuts, each measuring 15 inches, are made, thus turning the pad into a three-tail gauze bandage, with the central piece of wool for covering the respiratory entrance. The upper tail of one side should be passed round the side of the head above the ear and tied to the other corresponding tail. The lowermost tail should in a similar manner be passed under the ear and tied to the one on the other side, while the middle tail should be passed over the crown of the head, so as to fix the pad and prevent it from slipping down the neck. The cost of these home-made masks was only 2 cents each. The price compared very favourably with that of the metal-framed masks.

Some improvements have been suggested at various times.

(1) Soaking the mask in liquid disinfectants. Creosote and carbolic acid have a tendency to burn the nose and other parts of the face, while corrosive-sublimate solution causes skin trouble as well as gingivitis, loss of teeth, etc. For these reasons, any general application of disinfectants upon the mask is to be condemned. Besides, the role of the mask is a purely mechanical one, so that disinfectants are absolutely unnecessary for protection (178). (ii) Stanley (179) and Strong (180) recommend the insertion of small cotton plugs within the upper margin of the mask to fill the empty spaces on either side of the nose. Otherwise, in individuals with prominent noses, a lacuna is left which may prove dangerous, especially when stooping down in infected surroundings. Possibly our colleague Dr. Yuan was infected by omitting this precaution in 1921. It is perhaps significant that several instances are on record where infection seems to have occurred while stooping down to administer serum, etc. (iii) However well the mask is made, it is evident that its weakest points are the margins. When it does not fit well, dangerous gaps may occur. Certainly, this danger can be obviated to a large degree by careful adjustment. (iv) Strong (180) advises tying over the mask "another piece of gauze in which openings for the eyes are made and the ends cut into four tails and tied behind the head and neck". After Dr. Yuan's death (1921), we wore over our masks a hood made of cloth with a square piece of silk (4 by 6 inches) sewn in front of the respiratory entrances. The hood had two apertures for the eyes and was tucked inside the overall at the neck of the wearer (181). (v) Our latest mask. – Since the 1921 outbreak, I have further simplified the protective mask adopted at Mukden. As now made, the two layers of gauze enclose a 72-inch-thick piece of cotton pad, 4 inches by 6 inches (20 cm. by 30 cm.), and measure 2 feet 6 inches (75 cm. to 80 cm.) long. At either end are only two tails, one set being tied above the ear and the other beneath it. It has been found on thousands of occasions that this simple contrivance is quite sufficient except for those in immediate contact with coughing patients, where the hood (iv), with or without a mica front-piece, is desirable for additional safety. The mask should be changed after every visit to a plague ward. Police and other auxiliary personnel should use a fresh one at least once a day.

Broquet (182) recommended, at the Mukden Conference, another mask used occasionally by himself in 1911. This consisted of a canvas hood covering the whole head, could be tucked inside the overall at the neck and had in front a large mica window. Broquet stated that this mask could be easily sterilised by boiling.

Some experimental evidence regarding the value of masks in general may now be given. According to Shibayama (183), Masson "had made some experiments by holding gauze before the mouth of an infected patient, and putting agar-plates on the other side. These plates were found to be quite sterile, and it would therefore be sufficient to protect the doctor if patients always wore masks over their nose and mouth". This experience was contradicted by some preliminary experiments made with B. prodigiosus by Strong and his collaborators (184).

Barber and Teague experimented both with the cotton-gauze and the Broquet masks (185); the latter variety was somewhat modified by being made of heavy Canton flannel instead of the lighter material shown by Broquet; sheet celluloid was also used in place of mica. After a large series of experiments with B. prodigiosus, the following conclusions were reached by them:

"(i) The 'Mukden mask' in general use during the epidemic of pneumonic plague in Manchuria during the winter of 1910 to 1911 does not prevent the passage into the mouth and nostrils of B. prodigiosus when contained in small droplets sprayed around the mask. This mask consists of a pad of absorbent cotton held over the mouth and nose by a many-tailed gauze bandage. "(ii) A hood of heavy Canton flannel cloth, covering the entire head and tied in snugly at the neck, withstands much severer tests than does the Mukden mask. It does not, however, offer an absolute barrier to the passage of prodigiosus bacilli into the mouth and nostrils of the subject. This mask, with a window in front, is not more inconvenient nor more uncomfortable than the Mukden mask. "(iii) It is shown that the inefficiency of the Mukden mask is not due solely to the fact that the mask fails to conform to the con. figuration of the face but that the bacteria may pass directly through the mask, for a piece of moist cotton placed in the centre of the mask was found after the test to contain prodigiosus bacilli. "(iv) It is believed that, although masks hold back many bacteria that would otherwise pass into the mouth and nostrils, nevertheless their use during the recent epidemic of pneumonic plague in Manchuria lent a false sense of security, which may have led to the taking of unnecessary risks. We believe that these experiments fully justify the conclusion that masks such as were used in that epidemic do not offer an absolute protection against pneumonic plague."

Strong (180), while emphasising the importance of these experiments, was careful to point out that, nevertheless, the cotton-gauze mask appears to be "at least usually safe for practical purposes", because evidently the sputum droplets emitted by coughing patients are much larger and heavier than those obtained by artificial spraying. This point must, as we think, always be considered when evaluating the results of spraying experiments.

The protective value of masks was also amply studied during the 1918 influenza epidemic. As Heiser (186) summarises:

"Extensive experiments made in the United States during the epidemic of 1918 showed that, in order to prevent the passage of ordinary respiratory bacteria, at least 325 strands to the square inch of ordinary surgical gauze should be placed before the nose and mouth. This may be accomplished by using eight layers of 20 X 24 gauze (20 + 24 X 8= 352) or four layers of 40 X 44 gauze (cheese cloth) (40 + 44 X 4 = 336). The cheese cloth or the more closely woven material is said to give better results than the more numerous layers of loosely woven material."

Mason Leete (187), who worked with spraying of Staphylococcus pyogenes aureus, recommended butter muslin instead of surgical gauze; at least four layers should be used. This author thinks that a really protective mask "would have to consist of six to eight layers of muslin or similar material, and would need to be attached in an air-tight manner by means of an elastic band gripping all round the head and fitted with air-tight eye-pieces very much after the manner of the gas mask in use in the army". He realises, however, that such a mask would never be popular, and suggests therefore the use of a simpler mask which is as large as possible, comes up to just under the eyes above and down on to the neck below, and is held in position fairly tightly by elastic or tapes above the ears and round the neck, thus decreasing as far as possible round-the-corner' infection". Such a mask, according to Mason Leete, reduces materially the risk of infection. This writer sounds a warning: "Damping the mask has the effect of considerably increasing the permeability, and this fact should be borne in mind when masks have to be worn for any length of time."

During the 1920-21 Manchurian epidemic, we performed a number of experiments with our modified gauze-cotton masks. We tried to cultivate from the different layers of masks which had been actually worn in the plague wards for periods ranging from half an hour to four hours. In only one instance did we cultivate B. pestis and this was from the outer gauze layer of a mask which had been worn continuously for three hours. We did not find it possible to make animal tests, by which probably more accurate results might be obtained. The experiments were discontinued because, after Dr. Yuan's death, the additional hood with a silk front was used.

Chun, of our laboratory, experimented with gauze-cotton masks mounted in metal frames and sprayed emulsions of B. acidi lactici upon them. The results obtained were identical with those of Teague and Barber (188).

It can be seen that the experimental evidence is not entirely in favour of the absolute protection afforded by masks. We can but repeat, however, that it is impossible to base actual conditions always upon the results of experiments.

Our practical experience, gathered from the three large pneumonic plague epidemics of North China, where certainly conditions were rather favourable for a spread of infection, is undoubtedly in favour of the mask. We have seen that C. W. Young went even so far as to disregard the protective value of inoculation in favour of the mask in Shansi, in 1918. In our opinion, both measures may be combined with advantage.

In the 1910-11 epidemic, when the mortality among the sanitary staff was very heavy, the mask was not always used, especially in its early stages (189). Moreover, to be safe, a mask must not only be worn but properly worn. It must always be used near infected or suspicious individuals; it must be of an approved pattern, and not consist merely of a few layers of gauze; it must be well adjusted and in the case of the gauze-cotton mask cotton plugs must be inserted on both sides of the nose. Further, the use of the gauze-cotton mask ought to be combined with that of goggles for protection against conjunctival infection (190).

For those in immediate contact with a coughing patient, the additional use of a hood, preferably with a mica front-piece to allow a wide field of vision, is recommended. But it is not always easy to wear this close and cumbersome apparel during winter outbreaks (191). Members of our staff who wear glasses find it most inconvenient because of moisture collecting upon them. Even those without glasses are unable to endure it for any prolonged period because of the difficulty of breathing. In spite of the apparently favourable results from experiments performed in a tropical climate, we should not advise the general use of the hood alone, even were it easy to wear. In our opinion, the simple, cheap cotton-gauze mask is the best protective means at our disposal during pneumonic.plague epidemics. Thousands can be made at short notice without much expense in an emergency, and they are favoured both by the sanitary personnel and others concerned in an anti-plague campaign.

We may now proceed to the question when the mask is to be used.

For the medical staff, dressers and attendants in close contact with patients, it is absolutely essential, hence we recommend it for everyone on duty in the plague wards, in house-to-house inspection, and in segregation camps or wagons. The daily routine examination of a large number of contacts, especially in a confined atmosphere in winter, is accompanied by considerable risks to the personnel since a certain percentage of the segregated will show infection at one time or another.

Our Dr. Yu Shu Shen, while working at Sangyuan in 1921, was called at tea-time to see a child contact of eight years, and, thinking it was nothing dangerous, left off the mask which he had up to then regularly worn. He realised when too late that the child was coughing up plague bacilli, took infection that day and died six days later.

In the case of the burial and disinfecting staff, we also recommend the mask to be regularly used, although, from a theoretical standpoint, there is little or no immediate danger. For there is always a certain risk from relatives of the sick or dead who may be present at the time. Moreover, it is of much educational value in that they are constantly reminded of the necessity of taking precautions. The physicians should always set an example and not omit any necessary details. Through their reasonable behaviour, the influence exercised upon the masses will be immense.

In regions where neither the staff nor the population is familiar with pneumonic plague, the wearing of a mask may appear ridiculous or uncalled for. The experience of Tatungfu, during the early days of the Shansi outbreak in 1918, when both the magistrate and public resented the queer costume of the anti-plague staff during the New Year festivities, is one worth remembering. The same thing happened in Harbin during the first Manchurian epidemic (1910-11), when the people were not yet used to modern sanitary precautions, but those days are gone now, and the inhabitants of Manchuria welcome the co-operation of the anti-plague staff whenever an epidemic threatens.

Masks should also be worn when performing autopsies or post-mortem punctures because of the danger of droplet infection from splashing, etc. On such occasions it is best to wear goggles in addition, though our experience has been that the operator feels much impeded by them.

In the laboratory, when the rush conditions of work during a plague epidemic may be called abnormal, we are strongly in favour of both mask and goggles. Even under ordinary conditions, when an inhalation experiment or one entailing much handling of the B. pestis has to be performed, we believe the mask should not be neglected. The long line of laboratory infections recorded in an earlier chapter would perhaps have been avoided, at least partly, if this simple precaution had been taken.

In all experiments during the last fifteen years, we have insisted upon the wearing of masks by laboratory attendants whenever engaged upon duties in which infection from splashing or dust might be possible, such as cleaning cages and stables, removing and cremating infected animals, etc. Here again the educational" value of the mask is seen.

The value of masks in the case of patients is doubtful. Even were it possible to apply it generally, the practice would be cruel to the plague victim. For, besides the constant coughing and spitting, pneumonic patients suffer consciously or unconsciously from air hunger, and it is the duty of the physician to allay their sufferings and not add to them.

Furthermore, when the patients are accommodated in properly installed isolation hospitals, there is no real need for their permanently wearing a mask or being stifled by a gauze wrapper, since the only persons in contact will be the protected sanitary staff (192). Masks may be given with advantage for short periods of time, as when the patients are being transported. For serum administration, venesection, etc., the same may be done or-better still-use may be made of proper screens of calico or more solid materials. In the treatment room of our new isolation block we propose to have a glass screen with a hole through which the patient's arm may pass for the necessary operation. In this way, the patient will be entirely separated from the physician, who will have plenty of room and light for his observations without the accompanying risks of a single chamber.

The use of masks for contacts, who are usually accommodated not in individual cubicles but in small groups in common-rooms, wagons, etc., is certainly advantageous, and gauze-cotton masks should be placed at their disposal with proper instruction. A person with a mask may almost feel insured against a suspicious coughing neighbour. It will be very difficult, however, to enforce the wearing of masks and still more to have them properly worn. De Vogel (193) justly remarks that very little can be expected in this respect from untrained laymen. This was amply borne out by our observations in Manchuria, where for a time it was quite the fashion among the population at large to wear masks. We remember seeing a man in the street with a stiff (wire-framed) mask over the nose only, while he was serenely smoking a cigarette. Sometimes the masks were wrapped round the neck "as a protection against cold"! On the whole, we believe only one class of people is benefited by the general use of masks during epidemics, namely, those who sell all sorts of permanent "respirators" of an inadequate pattern at exorbitant prices.

A number of other precautions have been recommended for diminishing the danger of infection from patients. We have seen that in former times the doctors either did not come near the patients at all or turned their heads away, etc. Roux, in 1889, advised the examination of a plague patient for not longer than five minutes; this plan was followed in Asia Minor (194). Clemesha (195) advocates that "the nurse should be instructed to stand aside or behind the patient during a fit of coughing". Nikanoroff (196) suggests keeping dumb while visiting the patient and breathing only through the nose! These precautions may occasionally be helpful, but they are of limited importance because they cannot always be taken. Wherever possible, the patients should be accommodated in the open air or in half-open wards. We will deal with this matter in the next chapter.

Original text (scan)

Original text