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The epidemiology of diphtheria
PUBLIC
HEALTH T H E J O U R N A L OF
THE SOCIETY OF MEDICAL OFFICERS OF HEALTH No. 1.
Vol. LV.
OCTOBER,
1941
Editorial
Subscription 81s. 6d. per annum, post free, in advar.ce Single copies 2s. 6d. post free. " Public Health " is the Official Organ of the Society of
The Epidemiology o| Diphtheria
Medical O~eers of Health and a suitable medium for the advertisement of o~icial appointments vacant in the health service. Space is also available for a certain number of approved commercial advertisements. Application should be made to the Executive Secretary of the Society, at Tavistock House South, Tavistock Square, W.C.1. Telephone: Euston 3923. Telegrams: Epidauros, Westcent.
When new scientific discoveries are made workers are obliged to adopt designations which identify them. Not uncommonly later work reveals that the additions to nomenclature so introduced have been founded on erroneous assumptions. For instance, the name H. influenzae conveys the impression that this microorganism is the cause of influenza, and psittacosis was so called in, the belief that the disease was essentially a disease of the parrot family, which is now known to be not exactly the case. When Anderson, McLeod, and their colleagues discovered that there were distinct types of C. diphtheriae associated with different clinical forms of the disease they proved to be well justified in describing two of them as "" mitis '" and "'gram's," since, on the whole, they caused respectively milder and more severe toxic manifestations. A smaller group of micro-organisms, however, resisted inclusion in either of the two main types, as identified by their laboratory methods of classification, and they adopted the descriptive term "intermedius" to distinguish it, It is not clear whether they regarded this third type as being intermediate in its capacity to cause severe symptoms and death, but the term certainly conveys that impression. It soon became clear, however, that C. diphtheriae conforming to this intermediate type was common in other places than Leeds, and that it might cause symptoms and mortality at least as serious as the grav/s type. Recent studies by Prof. Hedley Wright of Liverpool* indicate that the intermedius type, while less frequent in its occurrence than either mitis or gray/s, is significantly and substantially more fatal in that city. His records cover 8,040 cases of diphtheria, bacteriologically verified, occurring over four years. Thirty per cent. were ~nitis infections, 51 per cent. grawis, and 19 per cent. intermedius. The three types pursued independent epidemiological courses, mitis and intermedius declining from the end of 1937 to the autumn of 1940, while gravis remained more or less stationary (with the usual seasonal fluctuations) until then. In the last quarter of 1940 grav/s rose sharply and the other two types also became aetually more prevalent than before, but less so relatively to gr~a/s. Thus, by a fairly gradual process, the percentages changed as f o l ! o w s : -
Contents Editorial PAGE
T h e E p i d e m i o l o g y of D i p h t h e r i a . . . . . . . . .
1
C o n t r o l of W a t e r S u p p l y in the U . S . A . . . . . . .
2
E x p e r i m e n t in T r a i n i n g
3
. . . . . . . . . . . .
P u b l i c E d u c a t i o n in H e a l t h
.........
3
More Health Propaganda . . . . . . . . . . . .
4
Speeial Artieles T r i c h i n i a s i s in Wales.
By N a n c y G. How e l l ,
M.R.C.S., L.R.C.P., D . P . t t .
.
.
.
.
.
.
.
.
.
5
Scabies--A Golden Opportunity. By C. W. Dix on, M.D., D.V.n . . . . . . . . . . . . .
10
W e l f a r e in P u b l i c Shelters. By M. A. C r e s w i c k Atkinson . . . . . . . . . . . . . . .
14
Obituary Dr. W i l l i a m R o b e r t s o n
. . . . . . . . . . . .
18
Dr. T. J. L. F o r b e s . . . . . . . . . . . . . . .
18
Dr. A. W. F o r r e s t e r
. . . . . . . . . . . .
18
. . . . . . . . . . . . . . .
18
Book Reviews Stammering
The Nursing Couple
. . . . . . . . . . . .
19
. . . . . . . . . . . . . . .
19
N e w s and Summaries C a n c e r Act, 1939
The Society of Medical Officers of Health Council Meeting
. . . . . . . . . . . . . . .
Mitis Inte,rmedius Gravis 1937 1940
20
... ...
41 17
25 13
* 1. Path. Bact., May, 1941, 52, 283.
34 70
Total 100 100
PUBLIC HEALTH Throughout the whole period, and with little variation from year to year, the percentage fatality rates were, mitis 2'2, intermedius 10'7, and gravis 6"3. For all types the fatality rate (which may have been artificially low by the inclusion of some carriers as cases) was 5"9. It has increased slightly in 1940 to 6"45, the largest difference between individual years being less than statistically significant. The declines in incidence of the mitis and the highly fatal intermedius infections have tended to balance one another, and a much larger proportion of all the deaths was caused by tho gravis type in 1940 than in 1937. When the incidence of cases is studied in age-groups there is found to be not much difference in age.distribution between the types except that a significantly • higher proportion of mitis occurs at the youngest ages, 0-4 years. The only age-group which shows a fall over the 4 years is 5-9, suggesting that school immunisation may be taking effect. As regards fatality, mitis is almost negligible over 5 years but at 0-4 it is serious enough (4"6.pef-6~n~.. At all ages interrnedius is most fatal,~anging from 15'1 per cent. at 0-4 years to ~4"5 over fifteen. The fatality of':'gr~_is drops from t0"1 per cent. to 1"7 per cent. at these ages. In Liverpool the t~ndency seen in other places for the fatality of diphtheria at 5-9 years to approach that among younger children is not evident. For intermedius and grc~is it is about twothirds of the rate at 0-4 years, and for mltis about a fourth. The causes of death associated with the several types are interesting. Of 53 deaths due to mitis, 28 were due to laryngeal obstruction or pneumonia, whereas only 14 of 422 due to the other types were so caused. The rest were toxic. This is in keeping with •experience elsewhere, and indicates that secular examination of types showing their epidemiological rise and fall js of practical importance as a guide to health departments in anticipating the ~clinical problems with which they are likely to be faced from time to time.
Control of Water Supply in the U.S.A. T h e American Public Health Association Committee on Water Supply * has recently undertaken a particularly opportune survey of the practices operative in the U.S.A. The findings, which are based on returns from areas varying in size and geographical location, show extreme divergence in the control exercised, whether in relation to the water delivered into distributing systems, readmitted to distributing systems after exposure to secondary contamination in open reservoirs, or delivered to the consumers. The Committee postulates that within reasonable limits water delivered into 'distributing systems should be free from coliform organisms. This criterion not only assures safety, but also gives added significance to the results of analyses Of tap samples. The Committee urges the necessity for additional local water-plant laboratories, because inquiry showed that samplifig programmes were often insufficient to give reasonable assurance of the quality of water delivered into the systems, the inadequacy being more marked where disinfecting processes were
*Amer. J. publ. filth., 1941, 81, Supplement pp. 75, 83,
OCTOBER employed. Secondary contamination in open reservoirs is a common hazard and one which in many undertakings is not being faced. The Committee feels that in view of present world conditions the possibility of sabotage and of contamination of water in open reservoirs with cultures of pathogenic organisms or poisons needs to be kept well in mind. Contamination of water after its admission into the system may be brought about by pollution in open reservoirs or by back syphonage, cross-connections, or repairs to the systems, and it is stressed that much remains to be done before tap water throughout the country is of assured safe sanitary quality. To this end an accurate and adequate record of the quality of the water as actually delivered to the consumer, measured at numerous and welldistributed taps over the distributing area, is of much importance. Local contamination which otherwise might remain undetected would in this way be discovered early and remedied. There is a growing tendency to treat supplies so as to maintain a slight chlorine excess throughout the distributing system, this being usually of the order of 0.1 p.p.m. In some cases, when ammonia is combined, a much higher figure is tolerated without the taste being objectionable. While the low chlorine concentrations, even though present throughout the distributing systems, do not afford much margin of safety against localised contamination, high chlorine concentrations seem to provide a real protection. No place using chloramine treatment and carrying residuals of 0-2 p.p.m, or more throughout the system reported any cases of localised contamination. The Committee on Waterways Pollution also dealt with the allied subject of standards of water purity. Standards of purity for streams, lakes, and coastal water, and for sewage and treatment of waste effluents from industrial plants cannot be established so as to be of general application. These must be laid down only in the light of known basic data and the extent of pollution. Apart from the U.S. Public Health Service standard of quality for drinking water used by common carriers in interstate traffic (which provides that the B. coli index shall not exceed an average of one per 100 c.c. and that not more than 5 per cent. of the samples collected shall have an index of 6 or more per 100 c.c.), there are no generally accepted and widely used standards. All bacterial standards of water purity are based on the B. coli index per c.c. or per 100 c.c., the coliform organisms being peculiarly suitable for this purpose because they are normal inhabitants of the intestinal tract of warm-blooded animals, are non-pathogenic, are excreted in large numbers, and are usually more resistant to unfavourable environments than most disease organisms. In determining the sanitary quality of water, therefore, they are probably the most reliable index of pollution. In regard to industrial water supplies, it is possible, apart from the presence of chemical constituents such as those which form scales in boilers, to produce in most industries a satisfactory supply from a raw water source, from which a safe and potable drinking water can be obtained. A limiting B. coli index of 50 per 100 c;c. is becoming generally accepted as a standard of quality for outdoor bathing waters, and also as a limiting value
HEALTH T H E J O U R N A L OF
THE SOCIETY OF MEDICAL OFFICERS OF HEALTH No. 1.
Vol. LV.
OCTOBER,
1941
Editorial
Subscription 81s. 6d. per annum, post free, in advar.ce Single copies 2s. 6d. post free. " Public Health " is the Official Organ of the Society of
The Epidemiology o| Diphtheria
Medical O~eers of Health and a suitable medium for the advertisement of o~icial appointments vacant in the health service. Space is also available for a certain number of approved commercial advertisements. Application should be made to the Executive Secretary of the Society, at Tavistock House South, Tavistock Square, W.C.1. Telephone: Euston 3923. Telegrams: Epidauros, Westcent.
When new scientific discoveries are made workers are obliged to adopt designations which identify them. Not uncommonly later work reveals that the additions to nomenclature so introduced have been founded on erroneous assumptions. For instance, the name H. influenzae conveys the impression that this microorganism is the cause of influenza, and psittacosis was so called in, the belief that the disease was essentially a disease of the parrot family, which is now known to be not exactly the case. When Anderson, McLeod, and their colleagues discovered that there were distinct types of C. diphtheriae associated with different clinical forms of the disease they proved to be well justified in describing two of them as "" mitis '" and "'gram's," since, on the whole, they caused respectively milder and more severe toxic manifestations. A smaller group of micro-organisms, however, resisted inclusion in either of the two main types, as identified by their laboratory methods of classification, and they adopted the descriptive term "intermedius" to distinguish it, It is not clear whether they regarded this third type as being intermediate in its capacity to cause severe symptoms and death, but the term certainly conveys that impression. It soon became clear, however, that C. diphtheriae conforming to this intermediate type was common in other places than Leeds, and that it might cause symptoms and mortality at least as serious as the grav/s type. Recent studies by Prof. Hedley Wright of Liverpool* indicate that the intermedius type, while less frequent in its occurrence than either mitis or gray/s, is significantly and substantially more fatal in that city. His records cover 8,040 cases of diphtheria, bacteriologically verified, occurring over four years. Thirty per cent. were ~nitis infections, 51 per cent. grawis, and 19 per cent. intermedius. The three types pursued independent epidemiological courses, mitis and intermedius declining from the end of 1937 to the autumn of 1940, while gravis remained more or less stationary (with the usual seasonal fluctuations) until then. In the last quarter of 1940 grav/s rose sharply and the other two types also became aetually more prevalent than before, but less so relatively to gr~a/s. Thus, by a fairly gradual process, the percentages changed as f o l ! o w s : -
Contents Editorial PAGE
T h e E p i d e m i o l o g y of D i p h t h e r i a . . . . . . . . .
1
C o n t r o l of W a t e r S u p p l y in the U . S . A . . . . . . .
2
E x p e r i m e n t in T r a i n i n g
3
. . . . . . . . . . . .
P u b l i c E d u c a t i o n in H e a l t h
.........
3
More Health Propaganda . . . . . . . . . . . .
4
Speeial Artieles T r i c h i n i a s i s in Wales.
By N a n c y G. How e l l ,
M.R.C.S., L.R.C.P., D . P . t t .
.
.
.
.
.
.
.
.
.
5
Scabies--A Golden Opportunity. By C. W. Dix on, M.D., D.V.n . . . . . . . . . . . . .
10
W e l f a r e in P u b l i c Shelters. By M. A. C r e s w i c k Atkinson . . . . . . . . . . . . . . .
14
Obituary Dr. W i l l i a m R o b e r t s o n
. . . . . . . . . . . .
18
Dr. T. J. L. F o r b e s . . . . . . . . . . . . . . .
18
Dr. A. W. F o r r e s t e r
. . . . . . . . . . . .
18
. . . . . . . . . . . . . . .
18
Book Reviews Stammering
The Nursing Couple
. . . . . . . . . . . .
19
. . . . . . . . . . . . . . .
19
N e w s and Summaries C a n c e r Act, 1939
The Society of Medical Officers of Health Council Meeting
. . . . . . . . . . . . . . .
Mitis Inte,rmedius Gravis 1937 1940
20
... ...
41 17
25 13
* 1. Path. Bact., May, 1941, 52, 283.
34 70
Total 100 100
PUBLIC HEALTH Throughout the whole period, and with little variation from year to year, the percentage fatality rates were, mitis 2'2, intermedius 10'7, and gravis 6"3. For all types the fatality rate (which may have been artificially low by the inclusion of some carriers as cases) was 5"9. It has increased slightly in 1940 to 6"45, the largest difference between individual years being less than statistically significant. The declines in incidence of the mitis and the highly fatal intermedius infections have tended to balance one another, and a much larger proportion of all the deaths was caused by tho gravis type in 1940 than in 1937. When the incidence of cases is studied in age-groups there is found to be not much difference in age.distribution between the types except that a significantly • higher proportion of mitis occurs at the youngest ages, 0-4 years. The only age-group which shows a fall over the 4 years is 5-9, suggesting that school immunisation may be taking effect. As regards fatality, mitis is almost negligible over 5 years but at 0-4 it is serious enough (4"6.pef-6~n~.. At all ages interrnedius is most fatal,~anging from 15'1 per cent. at 0-4 years to ~4"5 over fifteen. The fatality of':'gr~_is drops from t0"1 per cent. to 1"7 per cent. at these ages. In Liverpool the t~ndency seen in other places for the fatality of diphtheria at 5-9 years to approach that among younger children is not evident. For intermedius and grc~is it is about twothirds of the rate at 0-4 years, and for mltis about a fourth. The causes of death associated with the several types are interesting. Of 53 deaths due to mitis, 28 were due to laryngeal obstruction or pneumonia, whereas only 14 of 422 due to the other types were so caused. The rest were toxic. This is in keeping with •experience elsewhere, and indicates that secular examination of types showing their epidemiological rise and fall js of practical importance as a guide to health departments in anticipating the ~clinical problems with which they are likely to be faced from time to time.
Control of Water Supply in the U.S.A. T h e American Public Health Association Committee on Water Supply * has recently undertaken a particularly opportune survey of the practices operative in the U.S.A. The findings, which are based on returns from areas varying in size and geographical location, show extreme divergence in the control exercised, whether in relation to the water delivered into distributing systems, readmitted to distributing systems after exposure to secondary contamination in open reservoirs, or delivered to the consumers. The Committee postulates that within reasonable limits water delivered into 'distributing systems should be free from coliform organisms. This criterion not only assures safety, but also gives added significance to the results of analyses Of tap samples. The Committee urges the necessity for additional local water-plant laboratories, because inquiry showed that samplifig programmes were often insufficient to give reasonable assurance of the quality of water delivered into the systems, the inadequacy being more marked where disinfecting processes were
*Amer. J. publ. filth., 1941, 81, Supplement pp. 75, 83,
OCTOBER employed. Secondary contamination in open reservoirs is a common hazard and one which in many undertakings is not being faced. The Committee feels that in view of present world conditions the possibility of sabotage and of contamination of water in open reservoirs with cultures of pathogenic organisms or poisons needs to be kept well in mind. Contamination of water after its admission into the system may be brought about by pollution in open reservoirs or by back syphonage, cross-connections, or repairs to the systems, and it is stressed that much remains to be done before tap water throughout the country is of assured safe sanitary quality. To this end an accurate and adequate record of the quality of the water as actually delivered to the consumer, measured at numerous and welldistributed taps over the distributing area, is of much importance. Local contamination which otherwise might remain undetected would in this way be discovered early and remedied. There is a growing tendency to treat supplies so as to maintain a slight chlorine excess throughout the distributing system, this being usually of the order of 0.1 p.p.m. In some cases, when ammonia is combined, a much higher figure is tolerated without the taste being objectionable. While the low chlorine concentrations, even though present throughout the distributing systems, do not afford much margin of safety against localised contamination, high chlorine concentrations seem to provide a real protection. No place using chloramine treatment and carrying residuals of 0-2 p.p.m, or more throughout the system reported any cases of localised contamination. The Committee on Waterways Pollution also dealt with the allied subject of standards of water purity. Standards of purity for streams, lakes, and coastal water, and for sewage and treatment of waste effluents from industrial plants cannot be established so as to be of general application. These must be laid down only in the light of known basic data and the extent of pollution. Apart from the U.S. Public Health Service standard of quality for drinking water used by common carriers in interstate traffic (which provides that the B. coli index shall not exceed an average of one per 100 c.c. and that not more than 5 per cent. of the samples collected shall have an index of 6 or more per 100 c.c.), there are no generally accepted and widely used standards. All bacterial standards of water purity are based on the B. coli index per c.c. or per 100 c.c., the coliform organisms being peculiarly suitable for this purpose because they are normal inhabitants of the intestinal tract of warm-blooded animals, are non-pathogenic, are excreted in large numbers, and are usually more resistant to unfavourable environments than most disease organisms. In determining the sanitary quality of water, therefore, they are probably the most reliable index of pollution. In regard to industrial water supplies, it is possible, apart from the presence of chemical constituents such as those which form scales in boilers, to produce in most industries a satisfactory supply from a raw water source, from which a safe and potable drinking water can be obtained. A limiting B. coli index of 50 per 100 c;c. is becoming generally accepted as a standard of quality for outdoor bathing waters, and also as a limiting value