ACUTE INFECTIVE DISEASES.
Acute Infectious Diseases are characterised by certain definite
characters.
1.—_They are usually infectious or contagious._ It is preferable to use
these two terms as interchangeable. The modes in which infection is
received vary greatly with different fevers.
(1) Some can only be propagated by _inoculation_—the introduction
through an abraded surface of a minute quantity of the poison; as in
glanders and hydrophobia. Others, again, _may_ be introduced in this
way, but are usually acquired in another manner, as scarlet fever,
small-pox.
(2) Some are carried through the _atmosphere_. The contagium of
small-pox can be carried as far as any, while that of typhus fever only
traverses a few feet. The atmosphere acts as a conveyer of infection,
and the infectious matter must necessarily, in most instances, be in
the condition of dust to enable it to be wafted by currents of air or
disturbed by the movements of persons in an infected room.
(3) _Clothes_, books, and furniture are not uncommonly carriers of
infection. An old letter, or a lock of hair, has even after many years’
concealment in an enclosed space produced infection on being brought to
light. Woollen articles convey infection more easily than calico, and
dark clothes better than light coloured. A fever nurse’s clothes should
never be woollen, but some washable material.
(4) _Drinking water and food_ often form a vehicle for infection. Milk
and water are the two usual sources of infection; but uncooked food,
especially oysters and mussels, fed in sewage-polluted estuaries,
may produce the same effect. Cholera, enteric fever, dysentery, and
summer diarrhœa are the chief diseases from this source; but scarlet
fever and diphtheria occasionally have a similar origin. Milk may be
infected from having been handed by an infectious patient; or it may
possibly convey infection of the disease from which the cow at the time
is suffering, _e.g._, tuberculosis (see also page 312). Water may be
contaminated with sewage or the excreta of a single infectious patient.
2. _They retain their specific character and origin._ Small-pox never
produces scarlet fever, nor _vice versâ_; and it is found universally
that all the specific fevers “breed true,” each one retaining its
identity. More than this, a previous case of the same fever can nearly
always be detected on careful examination. Overcrowding and other
insanitary conditions diminish the resistance to infection, and may
increase its virulence.
3. _The behaviour of contagia_, when received into the system, is
characteristic of these diseases. There is first of all a period of
latency or _incubation_, during which no symptoms are manifested (see
page 287.) The incubation period is followed by the characteristic
symptoms of the particular fever, which disappear in a variable period,
leaving the patient, as a rule, more or less _insusceptible to a second
attack_ (see page 288).
Throughout the progress of the disease, except in the period of
incubation, the patient is able to communicate his disease to persons
about him who have not been rendered safe by a previous attack. The way
in which he thus communicates his disease varies in different cases. In
scarlet fever, the throat and skin are the chief sources of contagion;
in influenza, whooping-cough, and measles, the secretions from the
respiratory passages; in hydrophobia, the saliva; in enteric fever and
cholera, the vomit and stools.
=Prevention of the Spread of the Chief Acute Infectious Diseases.=—We
may divide these into three classes. (1) Those which are infectious by
contact with the patient or by the atmosphere around him. (2) Those in
which the intestinal and renal evacuations are almost alone infectious;
as enteric fever and cholera. (3) Those in which inoculation through
an abraded surface is generally if not always necessary to produce
infection.
SMALL-POX OR VARIOLA.
The contagium of small-pox is very tenacious of life. All parts of the
body, and all secretions and excretions contain it. As in typhus it
adheres to every article in the room, but unlike typhus is possessed
of great vitality, and if not exposed to the air may be active after
many years. There is considerable evidence indicating that the
contagion of small-pox may occasionally be _conveyed aerially_ for a
considerable distance, for even a quarter or half a mile from hospitals
in which small-pox patients are isolated. Whether this is the aerial
convection of infection, or in part at least due to carelessness of
persons connected with the hospital in their movements to and fro,
may remain an open question; but such hospitals in the midst of towns
are in practice a mistake; and in London small-pox has been found to
be more manageable since its small-pox patients were all conveyed to
extra-urban hospitals. The means for the prevention of small-pox are
(1) Isolation of infectious patients. (2) Disinfection of all infected
articles. For particulars under these two heads, see pages 319 and 324.
They must be carried out most rigidly in this disease. (3) Vaccination
and re-vaccination.
=Inoculation of small-pox= virus was largely practised as a means of
ensuring a comparatively mild attack, until it was made illegal in
1840. Sometimes, however, the attack thus produced was fatal, and every
case of inoculated small-pox became a new focus of infection, and a
source of high mortality, especially among young children.
=Vaccination.= About the year 1795 Dr. Edward Jenner was informed by
a milk-maid that she could not take small-pox, as she had already
contracted the natural cow-pox during milking. Many had previously
heard this same statement made; but Jenner was the first to put the
matter to the test. He took the lymph or virus from a woman who had
accidentally acquired cow-pox (vaccinia) from a cow, and inoculated
a boy with it. Some months later he inoculated the same boy with
small-pox, and a second time five years afterwards, without producing
small-pox on either occasion. Many other experiments were made, all
confirming these results; and in 1798 Jenner published his results.
The practice of vaccination gradually became more general, and was
followed by a progressive decrease in the mortality from small-pox.
Cow-pox or vaccinia is small-pox modified and mitigated by its
passage through the system of the cow, and not a spontaneous disease
of the cow. By its passage through the cow it has become attenuated
and altered. Instead of a general eruption all over the body, there
are vesicles only at the point of inoculation; and vaccinia, unlike
small-pox, is not communicable from person to person except by
inoculation. Furthermore it is in the vast majority of instances an
extremely mild ailment, not involving more than a few days discomfort.
Objection is taken to vaccination for small-pox on the ground that
serious diseases such as syphilis, erysipelas, and tuberculosis may be
inoculated at the same time. With lymph obtained from healthy children
this is impossible. Most of the cases of infection described have been
in reality hereditary disease, the local irritation of vaccination
serving to call into activity the morbid tendencies of the child. The
risk of such infection is infinitesimal; it may be reduced to zero by
moderate care and attention to detail. With modern antiseptic methods,
it is very rare for a vaccination sore to “go wrong.” Erysipelas may be
inoculated from dirt getting into a vaccination sore, as it may be into
any other sore; but with cleanliness this need not occur; and in fact
very seldom does occur. The risks are so small as to be negligible;
and if the protection afforded is one tithe of what is claimed for
it, no parent is justified in withholding this protection from his
infant. The _law as to vaccination_ requires that every infant shall be
vaccinated within six months of its birth, domiciliary visits for this
purpose being made by the public vaccinator. The obligation can only
be avoided by a statement on oath before a magistrate by the parent of
conscientious objection to vaccination.
=Does Vaccination protect against Small-Pox?= The registration of
deaths for the whole country only began in 1837, and before this
period death-rates from small-pox in terms of the population cannot
be accurately stated. Since that time there has been less or more
vaccination, so that it is difficult to obtain a true comparison
between periods with and without vaccination. Some indication of
the facts in London prior to 1801, when the first English census was
taken, may be obtained from the fact that in 1796 (two years before
the date of Jenner’s “Inquiry,”) small-pox reached its highest point,
causing 18½ deaths out of every 100 total deaths from all causes.
In the præ-vaccination period small-pox was 9 times as fatal as
measles, and 7½ times as fatal as whooping-cough (McVail), while
since vaccination has been practised it has sunk to an insignificant
position, when compared with these diseases. Dr. Guy found that in
London there were in 48 years of the seventeenth century ten epidemics,
in the whole of the eighteenth century 19 epidemics, and in the
nineteenth century no epidemic during which the deaths from small-pox
caused one-tenth or more than one-tenth of the total deaths from all
causes in any year. The worst year under obligatory vaccination in
London was 1871, in which barely 4½ per cent. of the total deaths
was due to small-pox, a proportion which was exceeded in the eighteenth
century ninety-three times.
In Sweden, the highest death-rate _before vaccination_ (1774-1800)
was 7·23 per 1,000 inhabitants, the lowest 0·31; under _permissive
vaccination_ (1801-1815) the highest 2·57 per 1,000 inhabitants, the
lowest 0·12; under _compulsory vaccination_ (1816-85) the highest 0·94
per 1,000 inhabitants, the lowest 0·0005. It has been stated that these
results, which might be extended by quotations from the statistics
of other countries, have been obtained not by vaccination, but by
improved sanitation, including in this term not only improved housing
and better water and food supply but also increased means of isolating
the infectious sick. Improved housing may by diminishing overcrowding
aid in diminishing the spread of this disease. Whether in view of the
immense increase in the proportion of the population which lives in
towns, it can be said that this has occurred is doubtful. Hospital
isolation undoubtedly prevents the spread of infection when promptly
effected. But a large share of the improvement in small-pox mortality
occurred before either hospital or home-isolation of small-pox patients
was generally enforced. There is no reason for supposing that impure
water or food, or nuisances about houses have any connection with the
origin or spread of small-pox, any more than they have with the origin
or spread of measles or whooping-cough; which still remain as prevalent
as in the past. Further light can be thrown on the subject by an
examination of the age-incidence of small-pox, and of its attack-rate
and severity in vaccinated and unvaccinated respectively.
The =age incidence of deaths from small-pox= has, since 1847, when
returns classified according to age became available, undergone a
remarkable alteration. Prior to 1870 the small-pox deaths in infants
nearly always formed 20 per cent. or more of the total mortality from
this disease, between 1870 and 1890 they did not greatly exceed 10 per
cent. of the total, while since 1890 they have again begun to form an
increasing proportion of the total small-pox mortality. At ages 1-5 the
change is even more remarkable. Before 1870 deaths at these ages nearly
always exceeded 30 per cent. of the total; since 1870 they have varied
between 5 and 14 per cent. of the total; and since 1890 they have,
like the proportion of deaths under one, again increased. At the higher
ages the proportion of deaths has correspondingly increased, so that
the curves of age incidence have become curiously inverted.
The lowered birth-rate can only account for a small portion of this
transference of the chief mortality due to small-pox from childhood to
adult life.
Furthermore it must not be supposed that the only change which has
occurred is that the deaths which formerly occurred in childhood now
occur in adult life. The death-rate at all ages has greatly declined.
The only explanation which in my judgment satisfactorily explains
this remarkable change in age-incidence of small-pox mortality is
the fact that vaccination protects children from small-pox and that
the protection diminishes, though it never entirely disappears, with
advancing years. This conclusion is confirmed by the evidence obtained
as to the proportion of vaccinated and unvaccinated attacked, and as to
the severity of the attacks occurring when a community is invaded by
small-pox.
=Attack-rate among Vaccinated.=—If the protective effect of
vaccination, like that of a preceding attack of small-pox, wears off,
it will not be expected that no attacks of small-pox will occur among
the vaccinated. For evidence of immunity from attacks we must examine
the records as to =revaccinated= persons exposed to infection. During
the six years 1890-95, out of a staff in the London small-pox hospitals
varying from 64 to 320, the percentage attacked by small-pox was _nil_,
except in 1892 when it was 1·4, and in 1893 when it was 1·9.
Taking the experience of towns in which during recent years epidemics
of small-pox have occurred, the following attack-rates have occurred.
By attack-rate is meant the percentage number of attacks occurring
among persons living in infected houses. By fatality is meant the
number dying out of 100 attacked.
┌────────────┬───────────────────────────┬──────────────────────────┐
│ │ ATTACK RATE UNDER │ ATTACK RATE OVER │
│ │ 10 YEARS OF AGE. │ 10 YEARS OF AGE. │
│ ├───────────┬───────────────┼───────────┬──────────────┤
│ │VACCINATED.│ UNVACCINATED. │VACCINATED.│ UNVACCINATED.│
├────────────┼───────────┼───────────────┼───────────┼──────────────┤
│_Dewsbury_ │ 10·2 │ 50·8 │ 27·7 │ 53·4 │
│_Leicester_ │ 2·5 │ 35·3 │ 22·2 │ 47·6 │
│_Gloucester_│ 8·8 │ 46·3 │ 32·2 │ 50·0 │
└────────────┴───────────┴───────────────┴───────────┴──────────────┘
=Severity (Fatality) among Vaccinated.=—The experience of the same
three towns comes out as follows:—
┌────────────┬───────────────────────────┬──────────────────────────┐
│ │ ATTACK RATE UNDER │ ATTACK RATE OVER │
│ │ 10 YEARS OF AGE. │ 10 YEARS OF AGE. │
│ ├───────────┬───────────────┼───────────┬──────────────┤
│ │VACCINATED.│ UNVACCINATED. │VACCINATED.│ UNVACCINATED.│
├────────────┼───────────┼───────────────┼───────────┼──────────────┤
│_Dewsbury_ │ 2·2 │ 32·1 │ 2.6 │ 18·7 │
│_Leicester_ │ 0.0 │ 14·0 │ 1.0 │ 7·8 │
│_Gloucester_│ 3·8 │ 41·0 │ 10·0 │ 39·7 │
└────────────┴───────────┴───────────────┴───────────┴──────────────┘
In view of such results as the above it is not surprising that the
Royal Commission, in their majority report, summed up the advantages of
vaccination as follows:
“(1) That it diminishes the liability to be attacked by the disease.
“(2) That it modifies the character of the disease, and renders it
(_a_) less fatal, and (_b_) of a milder or less severe type.
“(3) That the protection it affords against attacks of the disease
is greatest during the years immediately succeeding the operation of
vaccination. It is impossible to fix with precision the length of this
period of highest protection. Though not in all cases the same, if a
period is to be fixed, it might, we think, fairly be said to cover in
general a period of nine or ten years.
“(4) That after the lapse of the period of highest protective
potency, the efficacy of vaccination to protect against attack
rapidly diminishes, but that it is still considerable in the next
quinquennium, and possibly never altogether ceases.
“(5) That its power to modify the character of the disease is also
greatest in the period in which its power to protect from attack is
greatest, but that its power thus to modify the disease does not
diminish as rapidly as its protective influence against attacks, and
its efficacy during the later periods of life to modify the disease is
still very considerable.
“(6) That re-vaccination restores the protection which lapse of time
has diminished, but the evidence shows that this protection again
diminishes, and that, to ensure the highest degree of protection which
vaccination can give, the operation should be at intervals repeated.
“(7) That the beneficial effects of vaccination are most experienced
by those in whose case it has been most thorough. We think it may
fairly be concluded that where the vaccine matter is inserted in three
or four places, it is more effectual than when introduced into one or
two places only—and that if the vaccination marks are of an area of
half a square inch, they indicate a better state of protection than if
their area be at all considerably below this.”
SCARLET FEVER.
Scarlet Fever and Scarlatina are the same disease. It is extremely
infectious, the contagium retaining its virulence for protracted
periods. It occurs in epidemics at irregular intervals. During recent
years the type of scarlet fever has become greatly attenuated, and
this constitutes one of the difficulties of prevention, as the mild
form of the disease is apt to be overlooked. The _fatality_ per 100
persons attacked varies greatly with age. It is highest in children
under four, rapidly declining with increasing age. Hence the importance
of protecting children from attack in early life. Two results follow
from the wise precautions taken to prevent attack early in life. (_a_)
With each successive year of life the liability to attack, when exposed
to infection, diminishes; (_b_) the danger of the attack if it occurs
and its liability to be fatal becomes rapidly less with greater age.
The most common _mode of infection_ is by contact with a previous
patient. Outbreaks due to milk infected by a scarlatinal patient
also occur. Infected cream has also been known to convey infection.
In a milk outbreak the patients would be found chiefly among the
customers of a special dairyman, the cases occur almost simultaneously,
except secondary cases which may be infected from the first. The
_simultaneous_ occurrence of two or more attacks in one house,
especially if the same thing happens in a number of houses should throw
suspicion on the milk supply. It has been suggested that scarlet fever
may originate apart from human infection, from a special disease of the
cow, but the evidence on this point is inconclusive.
The _duration of infection_ is usually reckoned until the desquamation
of the skin is complete, _i.e._ about six or seven weeks from the
onset of the attack. Occasionally it is more protracted even though
desquamation is complete, infection appearing to persist in discharges
from the nose and ear and in sore places inside the nostril and
possibly in other parts. The period of greatest infectivity is in the
earlier part of the disease, when the throat is inflamed. The common
notion that the disease is most infectious during the later period,
that of desquamation, is erroneous. The micro-organism causing scarlet
fever has not certainly been identified. The measures of prevention are
those common to infectious diseases (page 317).
MEASLES.
Measles is an extremely infectious disease, before as well as after the
rash appears on the fourth day of the disease. The infectivity of the
catarrhal stage constitutes one of the main difficulties in preventing
its spread, as measles may be unrecognisable at this stage. The common
notion that measles and whooping-cough are comparatively harmless
infantile complaints will be dissipated by a study of the comparative
death-rate for the five years 1891-5 per million persons living in
England and Wales:—
ENGLAND AND WALES.—DEATH RATES PER MILLION OF POPULATION.
_Small-pox_ 20
_Measles_ 408
_Scarlet fever_ 183
_Typhus fever_ 4
_Enteric fever_ 174
_Whooping-cough_ 398
_Diphtheria_ 253
_Diarrhœa_ 630
It is a mistake also to suppose that measles and whooping-cough are
only serious when neglected. Such neglect greatly increases the
likelihood of death from bronchitis or pneumonia; but the diseases
themselves, especially measles, are frequently fatal during the acute
early stage. More children are attacked with measles under the age
of five than at any other age, and the greatest number between two
and four years of age. The greatest fatality is in the second year
of life, when it may be 24 per cent. of those attacked, as compared
with between two and three per cent. in the fourth year of life, and
a trifling amount at higher ages. These facts explain the folly of
allowing children to have an infectious complaint when another child in
the house is attacked, “to have it over at one trouble.” Such action
is pregnant with evil results. (1st) Severe cases occur, in which a
fatal result ensues; and even where death does not occur, the child
may be left weakly and very prone to become tuberculous. (2nd) Every
additional case forms a new centre of infection. It is like the old
practice of inoculation for small-pox; the individual is protected, but
becomes a source of danger to all around him. If there is only one
case of measles in a family the risk to neighbouring households is much
smaller than where several children are infected. (3rd) Every year that
a child’s attack can be delayed, increases his chance of recovery if he
is subsequently attacked, and diminishes the likelihood of his being
attacked.
The _duration of infection_ should be reckoned as at least three weeks.
The contagium of measles does not appear to hang about rooms with the
persistence of that of scarlet fever, and less stringent disinfection
is required.
WHOOPING COUGH.
Very few people have reached adult life without having suffered
from this disease, as well as measles. This is chiefly due to
the carelessness in mixing infected with healthy children. One
frequently hears the peculiar and characteristic cough of a child
with whooping-cough, in public assemblies, in railway trains, or in
the out-patient rooms of hospitals. The contagium of whooping-cough
is conveyed chiefly by the expectoration, which becoming dry, may be
scattered like that of phthisis, as dust. Clothing conveys infection
easily; visits to infected children should, therefore, be prohibited to
all who have to mix with susceptible children.
The _duration of infection_ should be reckoned as at least six weeks
from the first recognisable symptoms. It may be longer than this.
DIPHTHERIA.
This disease has become increasingly prevalent in the last ten years
after a period of only slight prevalence for about twenty-five years.
I have shown that epidemics of diphtheria occur during a succession of
years of protracted drought. Diphtheria is more common in girls than
boys, possibly owing to their more affectionate habits; and occurs
chiefly under ten years of age, the fifth year of life being that of
greatest prevalence. Unlike the acute infections hitherto considered,
the bacillus causing diphtheria has been identified and cultivated
in the laboratory (called the Klebs-Loeffler bacillus or diphtheria
bacillus). Direct infection from patient to patient is probably more
common than indirect infection by clothes, etc., though the latter
occurs. The infection may hang persistently about a house and its
belongings, in the absence of complete purification. When diphtheria
is prevalent slighter sore throats occur, sometimes before true
diphtheria is detected. This led to the theory that under conditions
of overcrowding, especially in schools, there occurred in the
micro-organisms causing these sore-throats “the progressive development
of the property of infectiveness.” Possibly these were slight
non-typical attacks of diphtheria. Such attacks occur also during
epidemics of diphtheria, and unless specimens (“throat swabs”) from
these sore-throats are examined bacteriologically, are likely to spread
diphtheria by attendance at school, etc. Aggregation in schools seems
to intensify the contagium of diphtheria. The practices of kissing, of
transferring sweetmeats from mouth to mouth, of cleaning slates with
saliva, are common means of spreading it. Effluvia from foul drains
and sewers have been commonly held to cause diphtheria. If they aid
in producing it, it is rather by lowering the vitality and causing
ordinary sore throat. Sore throats and catarrhs make the subjects of
them much more prone to diphtheria (see also page 117). Damp houses
have been stated to favour the development of diphtheria. Probably
they do so in the same way as effluvia from drains. It is likely that
the diphtheria bacillus has a saprophytic stage of existence in the
soil, as indicated by its excessive prevalence in dry warm years.
Besides direct infection from patient to patient and indirect infection
by _fomites_ (_i.e._ in clothing, etc.), milk occasionally causes
epidemics of diphtheria. The infection has been usually caused by the
handling of the milk by an infectious person. In certain outbreaks no
human contamination of the milk could be discovered; and it has been
surmised that an analogous disease in the cow may cause diphtheria in
man. This is still a moot point. Fowls, cats, and other animals are the
occasional victims of diphtheria, and may convey it to man.
The _duration of infection_ in diphtheria is usually less than six
weeks; but it may be much more protracted. In some instances long after
all naked-eye evidences of diphtheria has disappeared, bacteriological
examination may still show the presence of the diphtheria bacillus for
two or three months; in rare cases even longer. The protection afforded
by one attack of diphtheria against a second is slight and only
temporary. The _means of prevention_ are isolation and disinfection as
for other infectious diseases. Two additional means are available (_a_)
_bacteriological diagnosis_; (_b_) prophylactic injection of antitoxic
serum. Many sore throats without membrane on the throat are due to the
diphtheria bacillus. Even if membrane be present there may be doubt
as to whether the case is true diphtheria. Hence the importance of
bacteriological examination.
The patient’s throat is swabbed with cotton-wool which has been
rolled around a metal probe and sterilised. The wool is then smeared
over sterilised and solified blood serum in a test tube. It is then
incubated over night at a temperature of 37° C. Next morning the
minute growth that has occurred on the surface of the blood serum
is spread on a microscopic cover-glass, appropriately stained, and
examined microscopically. If diphtheria bacilli are present, they can
be recognised by their form and arrangement. The same means enable us
to ascertain when a patient has recovered, whether he is fit to be
released from isolation.
_Antitoxic serum_ has been found to be a valuable prophylactic and
curative agent.
The serum is obtained as follows: Sterilised broth is inoculated with
virulent diphtheria bacilli, and grown at 37° C. for a week or more.
The broth is then filtered through a Pasteur filter. The filtrate
contains _toxine_ free from bacilli. Some of this toxine is injected
under the skin of a horse. A few days later the dose is repeated,
gradually increasing amounts being injected until injection of further
quantities of the toxine is found experimentally not to increase
the antitoxic value of the horse’s blood serum. Next the horse is
bled. Its serum is found to have acquired the power of protecting a
guinea-pig against doses of the toxine of diphtheria which would
otherwise be fatal. Ten times the quantity of the horse’s serum which
will protect a guinea-pig (of 250 grammes weight) against ten times
the minimum fatal dose of the toxine is called an antitoxic unit.
The treatment of diphtheria in man by the antitoxic serum thus obtained
has proved to be remarkably successful. Furthermore, if a susceptible
person who has been exposed to the infection of diphtheria, is injected
with a small dose of antitoxic serum, he becomes temporarily immune,
and does not fall a victim to diphtheria. This is a most important
point especially for young children, who may already be incubating a
disease which but for this prophylactic injection might occur and prove
fatal.
TYPHUS FEVER.
This disease was formerly known as spotted or jail-fever, and for many
ages has been the scourge of prisons and armies, and all collections
of people living in overcrowded and insanitary districts. The history
of typhus is the history of human misery. It is essentially associated
with filth, overcrowding, and destitution; but when once established
by these conditions, it can be carried by infection to others who
live amidst healthy surroundings. It generally occurs in winter, when
overcrowding is greatest. With free ventilation, the disease cannot be
carried more than a few feet. It can be transmitted by clothing. The
micro-organism causing it has not been discovered. With the clearance
of the rookeries of our great towns, it is rapidly decreasing, and
appears likely to become extinct. The _means of prevention_, in
addition to the abatement of nuisances, including overcrowding, are
isolation and disinfection (pages 319 and 325).
RELAPSING FEVER.
This disease was formerly common in this country, but except in
some parts of Ireland has entirely died out. It is caused by a
micro-organism (_Spirillum Obermeieri_) which can be detected in the
blood. Inoculation of this will produce the disease in man or in
monkeys.
Epidemics of relapsing fever commonly follow in the track of typhus
fever; overcrowding and filth being especially associated with typhus,
and starvation with relapsing fever, hence its name of “famine fever.”
ENTERIC OR TYPHOID FEVER.
Enteric fever causes its highest death-rate in early adult life,
though it is not peculiar to any age. Eberth in 1880 discovered the
_Bacillus typhosus_ in the spleen and other organs of enteric fever
patients. This is commonly known as Eberth’s bacillus, and is the cause
of enteric fever. A few years later it was isolated and can now be
grown on agar or gelatine in laboratories. It closely resembles other
bacilli which are normal inhabitants of the human intestine; but can
be distinguished by certain tests. It is a small rod, rounded at its
ends, and from 2 to 4 µ long and three times as long as broad. In the
living state it is freely motile, and possesses a number of minute
cilia or flagella. Apart from other means of distinction between it
and other bacilli, _Grüber’s serum reaction_ enables its identity to
be ascertained. The bacillus suspected to be the _Bac.-typhosus_ is
cultivated in broth in the bacteriological laboratory. A small quantity
of blood is taken from the finger of a patient known to be suffering
from enteric fever. The serum is separated from the blood corpuscles
of this blood by a centrifugalising machine. A drop of the blood serum
is diluted with 100 drops of broth culture of the suspected bacillus.
If the latter is not the _Bac.-typhosus_, the individual bacilli when
a drop of the mixture is examined under the microscope, will continue
to move about freely; if it is the _Bac.-typhosus_, the bacilli will
adhere together in “clumps” and become immobile. Conversely a valuable
means of ascertaining whether a suspected case is really suffering from
enteric fever is secured, as this blood added to 30 times the amount of
a pure culture of the _Bac.-typhosus_ in broth will cause the latter to
“clump” within half-an-hour (_Widal reaction_). Higher dilutions are
usually unnecessary.
The chief means of spread of enteric fever is by the urine and fæces;
and nurses who have to empty bed-pans unless very careful to wash
their hands afterwards, using the nail-brush, are very liable to
become infected, probably when eating food afterwards. The urine in a
considerable proportion of cases, contains the typhoid bacilli, and
it is therefore most important that care should be exercised in the
cleansing of all chamber utensils, and that the urine as well as the
fæces should be rigidly disinfected (see page 331). The infectivity
of enteric fever has been underrated in the past. When patients with
this disease are nursed at home by relatives who do not appreciate the
full importance of the necessary precautions, it is rather the rule
than the exception for them to fall victims to its infection. Probably,
sometimes the infection has been scattered as dust, owing to small
particles of fæces or of urine having become dried on bed linen. The
most absolute cleanliness is essential in nursing this disease. In hot
climates there is reason to believe that infective dust may be blown
about from privies.
_Insanitary local circumstances_ are an important means of spreading
enteric fever. It is more prevalent where there are privies than
where there are pail-closets; and more prevalent where there are
pail-closets, than where water-closets are the rule. Defective drains
or soil-pipes are frequently found in houses in which enteric fever
originates, and there can be little doubt that the former are at least
partially responsible for the latter. The exact link is doubtful.
Probably infective dust is blown or aspirated into the room and is
inhaled.
The most common cause of enteric fever is _infected food or water_.
Of foods _milk_ not infrequently has been the means of spread of
enteric fever. Large epidemics have been traced to this source.
Usually this has arisen by washing the milk cans with or wilfully
adding contaminated water to the milk. _Water_, whether added to milk
or taken independently, must have contained the specific contagium
(the _Bac.-typhosus_) of enteric fever, to enable it to cause enteric
fever. Hence water from a contaminated stream is more likely to have
produced this effect than well-water, unless a patient has had enteric
fever in the house to which the well is attached, and his dejecta
have contaminated the water. Surface waters or spring waters may be
contaminated with sewage (as at Maidstone) or deep well waters through
fissures (as at Worthing) and thus widespread epidemics be produced.
After floods, rivers and wells are most likely to contain the specific
contagium of enteric fever, as at such times surface impurities from
middens, etc., are apt to be washed into the water. (See also pages 91
and 224).
The _means of prevention_ of enteric fever are the discovery and
removal of the cause of an outbreak, and the isolation of each patient
and disinfection of all discharges. An early means of diagnosis is
secured by Widal’s reaction. This is especially useful in cases not
presenting characteristic clinical symptoms. The recognition of a
disease or at least the suspicion of its presence is an indispensable
first step for the taking of precautionary measures.
CHOLERA.
Cholera, which was formerly so prevalent, now seldom occurs in this
country, and at each successive visit to England its inroads have
become less serious. At its last visit in 1893 it scarcely obtained
a footing in the country. Thus in the epidemic of 1854 in England it
caused 1080, in that of 1866 it caused 672, and in that of 1893 only
45 deaths per million of population. In this country at least it is
chiefly spread by infected water and foods, especially by infected
water; and the preceding figures form an excellent testimony to our
improvement in this respect. For particulars of the Hamburg outbreak,
see page 93. In its mode of prevalence and propagation it is very
similar to enteric fever, being infectious by means of the evacuations.
The means of prevention are the same as for enteric fever. Cholera was
shown by Koch to be caused by what is known as the _comma bacillus_ or
_spirillum_ of Asiatic cholera, so called because of its curved shape.
It is from 1·5µ to 2·6µ long and ·5µ broad. For the supposed connection
of enteric fever and cholera with movements of the ground-water, see
page 225.
SUMMER OR EPIDEMIC DIARRHŒA
is a most fatal disease among infants in the third quarter of
each year. It is chiefly a disease of urban life, and occurs to a
preponderant extent among the children of the artisan and still more
of the unskilled labouring classes. It is much less abundant in towns
which have adopted the water-carriage system of sewage than in those
retaining the conservancy methods of removal of excrement (page
198). Towns with the most perfect domestic and street scavenging
arrangements have the least epidemic diarrhœa. An impervious soil
favours a low diarrhœal mortality; while persons living on porous
soils usually have much diarrhœa. I have shewn elsewhere that given
two towns equally placed so far as social and sanitary conditions are
concerned, their relative diarrhœal mortality is proportional to the
height of the temperature and the deficiency of rainfall of each town,
particularly the temperature and rainfall of the third quarter of each
year. In other words there is a general inverse relationship between
rainfall and diarrhœa and a direct relationship between temperature and
diarrhœa. Thus wet and cool summers are adverse to diarrhœa. Ballard
concluded that the summer rise of diarrhœal mortality does not commence
until the mean temperature recorded by the 4-foot earth thermometer
has attained somewhere about 56° F., no matter what may have been the
temperature previously attained by the atmosphere. This is a convenient
index, as the summer warmth does not immediately cause diarrhœa. All
the above facts point to the conclusion that the fundamental condition
favouring epidemic diarrhœa is an unclean soil, the particulate
poison from which infects the air, and is swallowed most commonly
with food, especially milk. Thus, diarrhœa, like enteric fever, is a
“filth-disease.” As the contagium appears to gain entrance by food, the
following card of precautions which is distributed each year in the
poorer districts of Brighton may be reproduced here:
HOW TO PREVENT DIARRHŒA.
During the summer a large number of infants die from diarrhœa.
Scarcely a single baby who was being suckled dies from this cause.
It is evident, therefore, that in the prevention of this very fatal
summer disease, precautions as to food are most important.
Attention to the following points would save many infants’ lives:—
1. _Do not wean your infant during the hot months_ of July, August
and September. To begin artificial feeding during hot weather is very
dangerous.
2. If feeding by hand is absolutely necessary, carefully follow these
directions:
(_a_) _All milk should be boiled_ before being given to the infant.
(_b_) The infants’ food must be _prepared fresh each time_. (For
particulars see below.) Milk and water, and still more “pap” or patent
foods, if left two or three hours, “go bad,” and are then very highly
dangerous to the infant.
(_c_) _All jugs_ or other utensils used _for storing milk must be
scalded out_ and kept absolutely clean. They should be covered to
prevent access of dust.
(_d_) _The feeding bottle must be thoroughly scalded after each meal_,
and the tube thoroughly cleansed. It is best to use alternately
two boat-shaped bottles without tubes. If the bottle smells sour,
something is not clean, and the infant will suffer.
3. _Decomposing refuse_, such as decaying vegetables, bones,
fish-heads, &c., _is a fertile source of Diarrhœa_. _It should be
burnt_, and not placed in the dust-bin.
4. _Scrupulous cleanliness_ of the house, especially of the rooms where
food is stored, is most important. Dust in every form is dangerous to
health, and for removing it wet cleansing is preferable to dry. Thus
washing and scrubbing are safer means of cleansing floors, &c., than
sweeping.
5. _Report to the Sanitary Office_, Town Hall, any smells or choked
closet or drain.
DIRECTIONS FOR PREPARATIONS OF INFANTS’ FOOD.
=For a Child aged= =Mix and then boil= =For each Meal=
(1 part _fresh_ milk )
Under 6 weeks {2 parts water } 4 tablespoonsful.
(1 teaspoonful cream )
=Mix and then boil=
(1 part fresh milk )
6 weeks old {1 part water } 8 tablespoonsful.
(2 teaspoonsful cream)
=Mix and then boil=
(2 parts fresh milk )
From 3 to six months old {1 part water } 8 tablespoonsful.
(2 or 3 teaspoonsful )
cream.
The infant should _be fed at regular intervals only_, at first every
two hours, the interval being gradually increased.
The infant should _be fed slowly_.
If the milk as prepared above disagrees, _freshly boiled barley water_
should be used instead of water.
The _addition of cream is necessary_ because cows’ milk is poorer in
cream than mothers’ milk, and because it is very often made poorer
still by mixing with separated milk before sale. _Deficiency of cream
causes rickets._ A little sugar may also be added to the milk, but this
must not be regarded as a substitute for the cream.
TETANUS.
Tetanus or lockjaw is not infectious, but is conveyed to man by the
inoculation of a wound by dirt or earth which contains the tetanus
bacillus. For this reason it is more apt to follow injuries to the
hands or feet. Extreme cleanliness of wounds is the only practicable
preventive means. Little is known of the history of the tetanus
bacillus outside the body; and as to what soils contain it most
abundantly. Wounds contaminated by horse manure appear to be especially
dangerous.
GLANDERS.
Glanders is common in horses. It attacks the mucous membrane of the
nose, causing ulceration. It is extremely infectious. =Farcy= is a more
chronic form of the same disease, in which the so-called “farcy-buds”
are produced. Its prevention can best be ensured by killing both
actually diseased and suspected animals, if the latter give a reaction
to mallein. _Mallein_ is a product allied to tuberculin, obtained from
cultivations of the bacillus of glanders. It sets up febrile reaction
in glandered, but not in healthy horses. Further preventive measures
are the temporary closing of public drinking fountains for horses, and
the thorough cleansing and disinfection of stables. Men, especially
grooms, are sometimes infected by the horse, and the disease is
commonly fatal.
HYDROPHOBIA.
Hydrophobia is the disease in man which is caused by the bite of a
dog or other animal suffering from =rabies=. It is seldom if ever
communicated otherwise than by inoculation. The _incubation period_ in
the dog varies from three to six weeks, and in man is usually about the
same; but occasionally it is much longer, occasionally even more than a
year.
At the Pasteur Institute, Paris, patients who have been bitten by rabid
dogs are treated by the inoculation of an attenuated virus of rabies
derived from rabbits, with promising results.
Dogs only acquire rabies from dogs or other animals already rabid.
So far as is known, it does not arise _de novo_. Hence the necessity
for an extensive area of muzzling when cases of rabies occur. The
enforcement of this plan has greatly reduced the amount of hydrophobia
in this country in recent years. There has been much misplaced sympathy
with dogs on this score. In the dog the symptoms of rabies occur in
three stages: a _premonitory_ stage, in which the dog’s habits change,
he becomes morose and quiet, and dribbles; a _second_ stage, in which
he has paroxysms of fury, his voice is high-toned and croupy, and he
cannot swallow water; and a third or paralytic stage, in which his jaws
drop, he drags his hind legs and soon dies.
ERYSIPELAS.
Erysipelas occurs on various parts of the skin. It is caused by the
inoculation through an abraded surface of a virulent form of the same
streptococcus that commonly causes suppuration. It occurs chiefly in
debilitated subjects. Some persons are specially prone to it, and may
have many attacks. Erysipelas, like scarlet fever, occurs most in years
in which there is deficient rainfall; and is probably conveyed by dust.
It may spread, though exceptionally, from case to case.
YELLOW FEVER.
Yellow fever never occurs in England, except when imported from the
West Indies or other countries in which it is endemic. It clings to
seaport towns in hot countries; and as a permanent disease is only
found when the mean winter temperature is at least 68°-72° F. A frost
always stops an epidemic of this disease. The germs of this disease
are communicated by mosquitoes, which act as an intermediate host. Dr.
J. W. Lazear, although isolated from yellow fever cases, died of it
seven days after submitting to the puncture of an infected mosquito,
thus proving the communicability of this disease, and entitling himself
to an honoured position among scientific martyrs.
PLAGUE.
Plague is an Eastern disease, which occasionally shows a tendency
to become widely epidemic. It is due to a rod-shaped bacterium,
averaging ·8 µ to 1·6 µ in length, which does not form spores. In
its characteristic form patients suffering from this disease have
inflammatary swellings (buboes) of various glands: hence the name
_Bubonic Plague_. In other cases it simulates ordinary pneumonia,
typhus or septicaemia; or the patient may be so slightly ill as to
be able to walk about. It appears probable that the bacillus enters
the body through cracks or other lesions of the skin, possibly also
by inhaling infective dust. The rat is an important factor in the
spread of plague. Very commonly plague has been widely prevalent and
fatal among them before it attacks human beings. Rats also bring it in
ships from infected ports. Hence one of the most important preventive
measures is to kill all rats on board ship, before the cargo is
unloaded. This has been done by sulphurous acid fumigation in the
holds. The use of carbonic oxide gas will probably be found practicable
for the same purpose. Manson has put the importance of this point
tersely as follows: “To prevent cholera the tea-kettle, malaria the
mosquito net, and plague the rat-trap.” Flies may carry the infection
(page 281). It has been suggested that the fleas of rats carry the
infection (page 281).
ANTHRAX.
Anthrax is a very fatal disease in cattle and sheep, occasionally
in pigs. Butchers may inoculate themselves with it when dressing a
diseased carcase; the tanners similarly when handling the hide; and
woolsorters may inhale it when sorting wool derived from a diseased
animal (page 107). To prevent the latter, suspected wool must be
disinfected by steam, and special arrangements made for carrying off
the dust produced during sorting.
PUERPERAL FEVER
occurs after childbirth. It is caused like erysipelas by the
inoculation of septic material. This may be conveyed by dirty
instruments (syringes, etc.), or by dirty hands. Hence the importance
of extreme cleanliness of hands, finger-nails, and all articles used
during and after childbirth.
RHEUMATIC FEVER
has been commonly attributed to a damp condition of the atmosphere and
soil. I have elsewhere shown that this is a mistake, probably arising
from the fact that these conditions produce what are called “rheumatic”
pains, though they have no true relationship with acute rheumatism
(rheumatic fever). I have shown that rheumatic fever occurs chiefly in
very dry years, the excess of prevalence in such years being sufficient
to justify the use of the term “epidemic.” There is strong reason to
believe that rheumatic fever is an infective disease, derived, not from
other patients suffering from the same disease, but from some outside
micro-organism which is ordinarily saprophytic. It follows the rule
that when the lesion produced by an infective disease is deepseated
(in the joints in this instance), no infection can be communicated to
other persons. Some families are much more prone to rheumatic fever
than others.
INFLUENZA
is, like diphtheria, a somewhat mysterious infectious disease. Like
the latter it almost disappeared for a series of years, and then again
became epidemic in 1889. The previous epidemics of influenza in the
19th century had occurred in 1803, 1833, 1837-8, and 1847-8. The causes
of this recurrence of influenza are unknown. It is spread from person
to person by direct infection, the infection being conveyed by the
mucous discharge from the nose, throat, and lungs. Pocket-handkerchiefs
probably are largely responsible for conveying the infection as dust.
The disease is particularly fatal to the old; and these should not
expose themselves to possible sources of infection, as in public places
of assembly, during an epidemic. Every patient attacked with the
disease should remain indoors for at least ten days. This is in his own
interest, as he thus minimises the risk of such dangerous complications
as pneumonia; and it is his duty in the interest of the rest of the
community. Many lives might have been saved, had not influenzal
patients “struggled about” during the early stages of the disease.
MALARIA.
=Malaria=, or =Ague=, is a generic name given to a disease caused by
the invasion of the body by the _plasmodium malariæ_, discovered by
Laveran in 1880. It occurs in two chief types, remittent fever and
intermittent fever. For many generations it has been regarded as due
to a marshy condition of the soil, associated with decaying vegetable
matter, and a moderately high temperature. It is now clear that these
conditions are necessary, only because they are necessary for the
life of the mosquito. The well-known danger of being out of doors at
night in a malarious country is explained by the nocturnal habits of
the mosquito. The higher salubrity of the upper stories of houses is
explained by the fact that the mosquito does not rise high from the
ground; and of high-lying localities by their greater dryness. The
value of the mosquito net, of smoke, and of fire as protections from
malaria are due to their keeping mosquitos at a distance. The mosquito
clings to the puddle or swamp where she was born, and where she will
deposit her eggs. Hence the special danger of the immediate vicinity
of such collections of water. Thus the prevention of malaria resolves
itself chiefly into means for preventing the development of certain
species of Anopheles (page 282). The conditions necessary for the
multiplication of these are (1), an atmospheric temperature from 75°
to 104° F.; (2) collections of fresh or slightly brackish water; and
(3) the presence in these of low forms of animal and vegetable life. We
have already described the cycle of life of the _plasmodium malariæ_
(page 282). Man is the chief, if not the only source, from which
the mosquito derives this parasite. In native communities the young
children, even when apparently not ill with malaria, nearly always
harbour these parasites in their blood corpuscles. Hence the importance
of Europeans having their dwellings as remote as possible from native
houses. Mosquitos do not travel far.
Instances of the prevalence of malaria in the absence of mosquitos are
not substantiated. The outbreaks of malaria where the soil has been
disturbed after long lying uncultivated, probably mean the formation of
puddles favourable to the breeding of the larvæ of mosquitos.
The necessary preventive measures are classified by Manson as:
1. Suppression of mosquitos.
2. Prevention of infection of mosquitos.
3. Prevention of infection by mosquitos.
The =suppression of mosquitos= involves the draining or filling in of
swamps and ponds, the cleansing and canalisation of sluggish streams,
and the afforestation of hills to prevent floods. Cultivation of rice
and other plants entailing the prolonged flooding of land should
be restricted to fields remote from dwellings. Subsoil drainage is
helpful. The “painting” of stagnant waters with petroleum, which should
be renewed every week or two, frees water for a considerable time from
the larvæ of mosquitos. Eucalyptus and other balsamic trees may help to
dry up pools, &c.
The =prevention of infection of mosquitos= is secured by insisting on
all malarial patients using mosquito nets. This prevents the access of
mosquitos. At the same time patients should vigorously and persistently
take quinine, which kills the malarial parasites in the blood, and thus
diminishes and finally removes the danger to other persons produced by
the intermediation of the mosquito.
The =prevention of mosquito bites= is secured by rendering the house
mosquito-proof by filling in all openings by fine wire gauze, and by
having mosquito curtains to all beds; also by fumigating the rooms
occasionally with the dried flowers of the chrysanthemum, by strict
cleanliness of rooms, and by flushing them with sunlight. The proof of
the mosquito theory as to the causation of malaria has been recently
supplied by two test experiments. (_a_) In the first, a number of
mosquitos which had been fed on the blood of malarious patients were
sent to London from Rome. These were allowed to bite Dr. Manson’s
son, who had never previously had malaria. A few days later he had a
characteristic attack of fever. Malarial parasites were found in his
blood. He recovered in a week’s time after free dosage with quinine,
and the parasites disappeared from his blood. He suffered from a slight
relapse about a year later. (_b_) On a fever-haunted spot in the Roman
Campagna a wooden hut was built, and Drs. Sambon and Low, and three
others took up their abode here during the malarious season, the only
precautions taken being the use of mosquito nets and wire screens in
doors and windows. They went about the country daily, but were always
home before sunset. They all remained at the end of the season free
from malaria.