HUMIDITY AND INFLUENZA VIRUS

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736 THE ACT IN ACTION——IIUMIDITY AND INFLUENZA VIRUS guardians if they are minors) ; in column 2 a code letter or letters indicates the service given ; column 6 shows the money claimed from the State ; while column 5 gives the total amount the doctor intends shall be paid for his services by State and patient combined. To regularise the recovery of fees from the patient the report asks that " every general medical practitioner should have the right to charge and recover a fee additional to that payable from the Fund wherever circumstances, in his opinion, warranted it." Since the patient is no longer to be asked to sign the claim form, it is recognised that some alternative method of checking the claims made by practitioners is necessary. It is accordingly suggested that the Department devise a system of verification of service as an alterna- tive to the patients’ certification, as, for example, postal inquiry from a proportion of the patients of each practitioner. In addition, it is recommended that all practitioners be required to maintain adequate medical records of their patients in support of all claims made, and that these records and daily diary sheets be subject to inspection by medical practitioners duly appointed for that purpose." But it looks as though the committee doubts whether these methods of sample and scrutiny will be really effective ; for later we are told that it " discussed the practicability of prescribing limits to the numbers of patients to be seen daily or, alterna- tively, of prescribing a limit to the amount payable from the Fund to an individual practitioner. It considered that, in view of the wide variation in local conditions, types of patients, and the capacity of practitioners no fixed or arbitrary limits could be prescribed. Nevertheless, there are substantial grounds for believing that an average of, say, thirty attendances [items of service) daily is the maximum number practicable for an efficient and conscientious practi- tioner, and the Committee considers that Local Investigating Committees [consisting of local doctors with a medical officer of the health department] should be vigilant to investigate cases which habitually exceed the figure mentioned." As it appears from the other side of the world, this system which our colleagues in New Zealand are arranging for themselves is by no means attractive. If the Minister of Health here were to propose such a combination of snooping and sanctions he would be felt to have exceeded all reasonable bounds. Moreover, the object of the new plan is to support a method of payment which New Zealanders themselves admit does not encourage good medicine. In his presidential address this year Mr. J. A. JENKINS, president of the N.Z. branch of the B.M.A., said : , "It is the quality of the medical service that should count, not the quantity. The present system pays premiums for quantity and penalises care, thought, and time spent. This is basically wrong.’’ But even he could see no alternative to the fee-for-service - the salaried service, the capitation system, in fact anything that departs from what is ingrained in us is bound to fail’’—and he based his hopes on placing administration in the hands of a permanent, pre- dominantly medical, corporate body, and on the levying of additional fees for every conceivable item the patient needs. He believed that " if the govern- ment ... placed a small financial barrier between patient and doctor, patient, and chemist, and patient and hospital, many of the present abuses would cease at once." Would they ? We wonder. But then we have never had quite the same dislike (in principle) of capitation fees, nor the same faith in the fee-for- service. In the next year or two this country will have to find whether a capitation system embracing the whole population is compatible with high standards of practice. Meanwhile, if the New Zealand govern- ment accept their committee’s recommendations, New Zealand will be ascertaining whether the admit- tedly unsatisfactory trends of her practitioner service can be reversed by altering the method of claiming fees. Annotations THE ACT IN ACTION UNDER this title we propose to publish a short series of occasional articles on the working of the National Health Service during its first few months. They will describe some of the difficulties encountered and some of the defects observed. Signs of strain can be instructive even when they appear in the less vital parts of an organism, and we shall begin by examining one or two of the most conspicuous. The opening article deals with the supply of spectacles. HUMIDITY AND INFLUENZA VIRUS IT is now recognised that the most satisfactory means of preserving most viruses is to dry them in vacuo from the frozen state. By this method the virus is rapidly desiccated past the presumed critical degree of moisture at which its susceptibility to external influences is greatest. Similarly, it has been shown that smallpox virus, in infected crusts or in vesicle fluid dried on glass slides at room temperature (22°C), and foot-and-mouth virus in cattle saliva, will survive and remain infective for periods of several weeks to a year or more (smallpox crusts) under natural conditions. According to Sir Leonard Rogers,2 these findings support his oft-repeated argument that the spread and prevalence of smallpox is least at periods of high relative humidity of the atmosphere. In exploring the epidemiology of influenza, a number of attempts have been made to estimate the survival of the virus under more or less natural conditions. For example, Edward 3 showed that when a 5% suspension of infected mouse lung in normal human saliva was allowed to dry on glass slides at room temperature, only 1% of the virus could be recovered when drying was complete. He also found that when pieces of sheet were impregnated with a given quantity of mouse-lung virus, and the virus was allowed to dry under different conditions, much less virus was recovered when drying was slow because the humidity of the atmosphere was high. Loosli et a1.,4 in Chicago, demonstrated that influenza virus dispersed into the air is killed much more swiftly in humid than in dry air, and it has not been shown that when pneumococci type i, suspended in broth, saliva, or 0-5% saliva, are sprayed into the atmosphere, their mortality is very high at relative humidities in the vicinity of 50%. (At humidities above or below this value they survived for long periods.) Though a similar type of pattern was obtained with staphylococci, the results were not nearly so striking, which makes it probable that the effect of humidity depends on the structure of the micro-organism. From 1. Downie, A. W., Dumbell, K. R. Lancet, 1947, i, 550. 2. Rogers, L. J. Hyg., Camb. 1948, 46, 19. 3. Edward, D. G. Lancet, 1941, ii, 664. 4. Loosli, C. G., Lemon, H. M.. Robertson, C. H., Appel, E. Proc. Soc. exp. Biol. Med. 1943, 63, 205. 5. Dunklin, E. W., Puck, T. T. J. exp. Med. 1948, 87, 87.

Transcript of HUMIDITY AND INFLUENZA VIRUS

Page 1: HUMIDITY AND INFLUENZA VIRUS

736 THE ACT IN ACTION——IIUMIDITY AND INFLUENZA VIRUS

guardians if they are minors) ; in column 2 a codeletter or letters indicates the service given ; column 6shows the money claimed from the State ; whilecolumn 5 gives the total amount the doctor intendsshall be paid for his services by State and patientcombined. To regularise the recovery of fees fromthe patient the report asks that " every generalmedical practitioner should have the right to chargeand recover a fee additional to that payable fromthe Fund wherever circumstances, in his opinion,warranted it."

Since the patient is no longer to be asked to signthe claim form, it is recognised that some alternativemethod of checking the claims made by practitionersis necessary.

It is accordingly suggested that the Departmentdevise a system of verification of service as an alterna-tive to the patients’ certification, as, for example,postal inquiry from a proportion of the patients ofeach practitioner. In addition, it is recommendedthat all practitioners be required to maintain adequatemedical records of their patients in support of allclaims made, and that these records and daily diarysheets be subject to inspection by medical practitionersduly appointed for that purpose."

But it looks as though the committee doubts whetherthese methods of sample and scrutiny will be reallyeffective ; for later we are told that it

" discussed the practicability of prescribing limits tothe numbers of patients to be seen daily or, alterna-tively, of prescribing a limit to the amount payablefrom the Fund to an individual practitioner. Itconsidered that, in view of the wide variation in localconditions, types of patients, and the capacity ofpractitioners no fixed or arbitrary limits could beprescribed. Nevertheless, there are substantial groundsfor believing that an average of, say, thirty attendances[items of service) daily is the maximum numberpracticable for an efficient and conscientious practi-tioner, and the Committee considers that LocalInvestigating Committees [consisting of local doctorswith a medical officer of the health department] shouldbe vigilant to investigate cases which habituallyexceed the figure mentioned."

As it appears from the other side of the world,this system which our colleagues in New Zealand arearranging for themselves is by no means attractive.If the Minister of Health here were to propose sucha combination of snooping and sanctions he wouldbe felt to have exceeded all reasonable bounds.Moreover, the object of the new plan is to supporta method of payment which New Zealanders themselvesadmit does not encourage good medicine. In his

presidential address this year Mr. J. A. JENKINS,president of the N.Z. branch of the B.M.A., said :

, "It is the quality of the medical service that shouldcount, not the quantity. The present system payspremiums for quantity and penalises care, thought,and time spent. This is basically wrong.’’ But evenhe could see no alternative to the fee-for-service- the salaried service, the capitation system, in factanything that departs from what is ingrained in usis bound to fail’’—and he based his hopes on placingadministration in the hands of a permanent, pre-dominantly medical, corporate body, and on the

levying of additional fees for every conceivable itemthe patient needs. He believed that " if the govern-ment ... placed a small financial barrier betweenpatient and doctor, patient, and chemist, and patientand hospital, many of the present abuses would cease

at once." Would they ? We wonder. But thenwe have never had quite the same dislike (in principle)of capitation fees, nor the same faith in the fee-for-service. In the next year or two this country willhave to find whether a capitation system embracingthe whole population is compatible with high standardsof practice. Meanwhile, if the New Zealand govern-ment accept their committee’s recommendations,New Zealand will be ascertaining whether the admit-tedly unsatisfactory trends of her practitioner servicecan be reversed by altering the method of claimingfees.

Annotations

THE ACT IN ACTION

UNDER this title we propose to publish a short seriesof occasional articles on the working of the NationalHealth Service during its first few months. They willdescribe some of the difficulties encountered and someof the defects observed. Signs of strain can be instructiveeven when they appear in the less vital parts of anorganism, and we shall begin by examining one or twoof the most conspicuous. The opening article dealswith the supply of spectacles.

HUMIDITY AND INFLUENZA VIRUS

IT is now recognised that the most satisfactory meansof preserving most viruses is to dry them in vacuofrom the frozen state. By this method the virus is

rapidly desiccated past the presumed critical degree ofmoisture at which its susceptibility to external influencesis greatest. Similarly, it has been shown that smallpoxvirus, in infected crusts or in vesicle fluid dried on glassslides at room temperature (22°C), and foot-and-mouthvirus in cattle saliva, will survive and remain infectivefor periods of several weeks to a year or more (smallpoxcrusts) under natural conditions. According to SirLeonard Rogers,2 these findings support his oft-repeatedargument that the spread and prevalence of smallpoxis least at periods of high relative humidity of the

atmosphere.In exploring the epidemiology of influenza, a number

of attempts have been made to estimate the survival ofthe virus under more or less natural conditions. For

example, Edward 3 showed that when a 5% suspensionof infected mouse lung in normal human saliva wasallowed to dry on glass slides at room temperature,only 1% of the virus could be recovered when dryingwas complete. He also found that when pieces of sheetwere impregnated with a given quantity of mouse-lungvirus, and the virus was allowed to dry under differentconditions, much less virus was recovered when dryingwas slow because the humidity of the atmosphere washigh. Loosli et a1.,4 in Chicago, demonstrated thatinfluenza virus dispersed into the air is killed muchmore swiftly in humid than in dry air, and it has notbeen shown that when pneumococci type i, suspendedin broth, saliva, or 0-5% saliva, are sprayed into theatmosphere, their mortality is very high at relativehumidities in the vicinity of 50%. (At humidities aboveor below this value they survived for long periods.)Though a similar type of pattern was obtained with

staphylococci, the results were not nearly so striking,which makes it probable that the effect of humiditydepends on the structure of the micro-organism. From1. Downie, A. W., Dumbell, K. R. Lancet, 1947, i, 550.2. Rogers, L. J. Hyg., Camb. 1948, 46, 19.3. Edward, D. G. Lancet, 1941, ii, 664.4. Loosli, C. G., Lemon, H. M.. Robertson, C. H., Appel, E. Proc.

Soc. exp. Biol. Med. 1943, 63, 205.5. Dunklin, E. W., Puck, T. T. J. exp. Med. 1948, 87, 87.

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what is known of the tubercle bacillus, it is evidentthat the conditions necessary for its inactivation willdiffer from those required for the pneumococcus. Certain

experiments indicated that the deleterious effect of

50% humidity on the pneumococcus might be due toincreased salt concentration, and similar results havebeen obtained with influenza virus suspended in a brothcontaining 5 g. of sodium chloride per litre. 6 (Normalhuman saliva has only about a tenth of the amount ofsalt that physiological saline contains.) These Americanexperiments, however, did not include tests with influenzavirus suspended in human saliva with and withoutdialysis, which would give crucial information about therole of salt. Edward has suggested that the inactivationof the virus in saliva during drying might be causedby the lysozyme-like agent in the saliva, which mightwell have a maximum effect at a relative humidity of50%.

It is obvious that many factors besides humidity playa part in producing an epidemic. But it might beuseful to ascertain whether maintenance of the relativehumidity at a high level will control the spread ofinfluenza in a closed community.

TRACE ELEMENT PIONEERS

IN 1937, when Bennetts and Chapman 7 establishedthat copper deficiency was the cause of enzootic ataxiain- Western Australia, not much was known about traceelements in nutrition. The subsequent advances in thisfield must largely be ascribed to the stimulus applied bythe successes of these and other pioneers.

In 1928, after a long series of studies, Hart and hiscolleagues 8 at the University of Wisconsin had shown thatcopper as well as iron was essential for the formationof haemoglobin in the rat, but it was not until 1933 thata disease of economic importance was shown to be due tocopper deficiency. This was " liksucht," a wastingdisease of cattle in Holland which Sjollema 9 cured withcopper sulphate. The enzootic ataxia on which Bennettsand his associates did their classic work is a demye-linating disease of the unborn or unweaned lamb, pro-ducing a typical degeneration in the spinal cord whichis responsible for the ataxia, usually affecting the hindlimbs only. Nutritional disturbances as a rule precedeand almost invariably accompany the ataxia. From1932 onwards, on chemical, clinical, and pathologicaldata, Bennetts 10 built up a working hypothesis thatthe disease was due to lead poisoning. In his first trials,ammonium chloride, as a " deleading

"

agent, was fed togestating ewes and gave very satisfactory results. Ina later season the results were inconsistent and it wasfound that a very pure sample of ammonium chloridedid not prevent the ataxia. A spectrographic study ofthe effective and ineffective samples of ammoniumchloride and of livers from affected and normal lambsdisposed of the lead hypothesis and suggested that copperdeficiency was a more probable cause of the disease.In the next lambing season the administration of copperto the gestating ewe was found to prevent ataxia in thelamb. This was a discovery of major importance to theAustralian sheep industry, and, coupled with his pre-vention of " falling disease " in cattle with copper supple-ments," has earned for Dr. Bennetts and the WesternAustralian department of agriculture world-wideappreciation.Another important early success in trace-element

therapeutics, also achieved in Australia, was that of

6. Lester, W. Ibid, 1948, 88, 361.7. Bennetts, H. W., Chapman, F. E. Aust. vet. J. 1937, 13, 138.8. Hart, E. B., Steenbock. H., Waddell, J., Elvehjem, E. A.

J. biol. Chem. 1928, 77, 797.9. Sjollema, B. Biochem. Z. 1933, 267, 151.

10. Bennetts, H. W. Aust. ret. J. 1932, 8, 137 and 183 ; Ibid, 1933,9, 95 ; J. Coun. sci. industr. Res. Aust. 1935, 8, 61.

11. Bennetts, H. W., Harley, R., Evans, S. T. Aust. vet. J. 1942,18, 50.

E. J. Underwood and J. F. Filmer. They were investi-gating a fatal disease of sheep and cattle in localisedareas of Western Australia, for which Filmer 12 suggestedthe name " enzootic marasmus," the principal symptomsbeing progressive emaciation and anaemia. The diseasehad been prevented by the administration of limonite(Fe20aHQ0 and was thought to be due to iron deficiency.Analysis of the pastures and of organs of affected animals,and finally the prevention of the disease with an almostiron-free extract of limonite, showed that this hypothesiswas wrong.i3 By a series of fractionations of this extractFilmer and Underwood 14 finally traced the curative

property to cobalt, which invariably checked both thewasting and the anaemia. It is interesting to note thatLester Smith and the American group working on

the anti-pernicious-ansemia factor of liver agree that thefactor contains cobalt.15 5

DETAILS ABOUT ISOTOPE SUPPLIES

IN their statement published in our issue of Sept. 18(p. 469) the Medical Research Council gave details of theconditions under which radioactive isotopes can now beobtained for research and therapy. Radioactive isotopesrequire very careful handling by special techniques notnormally part of laboratory methods, and with thesedifficulties in mind the M.R.C. pointed out that stableisotopes of some useful elements were available fortracer research which could be used without any of the

protective measures needed for radioactive isotopes.But the estimation of stable isotopes has to be donewith a mass spectrometer, a complicated instrumentcosting about ;S;:2000 and calling for more technical

knowledge than most medical workers possess.The Ministry of Supply have now circulated some

further information about the obtainable radioactiveisotopes and also about stable isotopes and their estima-tion. At present the Atomic Energy Research Establish-ment at Harwell is working with a low-energy pile whoseusefulness, so far as medically interesting isotopes areconcerned, is limited. A larger pile is being constructed,and when in operation (no likely date is mentioned) itwill produce isotopes of specifications similar to thosenow provided by the U.S. Atomic Energy Commission.The low-energy pile has been used to produce radio-sodium(N a24), radiopotassium(K 42), and radiobromine

(Br82). These isotopes are useful in biological research,and since they have half-lives of only a few hours theycannot be imported. The low-energy pile has also

produced some radiophosphorus(P32) and radio-iodine(P31) pure enough for use in therapy, but the amountsare too small to be of practical value. When the largepile is operating at full power it will provide these andother isotopes in quantities sufficient to meet all expecteddemands for scientific and industrial, as well as medical,uses. In the meantime isotopes are being imported,mainly from the U.S.A., and supplies are necessarilylimited to the longer-lived isotopes like radio-iron

(Fe59, half-life 47 days) and radiophosphorus (half-life14 days).The stable isotopes now obtainable are those of nitro-

gen(N’5), carbon(C13), and oxygen(018). The nitrogenand carbon isotopes have been imported from America,but both will soon be manufactured in this country.The Genatosan Co. at Loughborough is making anenriched N15 on a commercial scale. At Harwell aplant for the production of C13 is nearing completion,and one for the production of 018 will be ready in aboutthree months’ time. These stable isotopes are thereforelikely to be fairly plentiful before long. With regard toestimation, there are two mass spectrometers at the

12. Filmer, J. F. Ibid, 1933, 9, 163.13. Filmer. J. F., Underwood, E. J. Ibid, 1934, 10, 83 ; Ibid. 1935,

11, 84.14. Filmer. J. F., Underwood, E. J. Ibid, 1937, 13, 57.15. Lester Smith, E. Nature. Lond. 1948, 162, 144.