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FLOTSAM AND JETSAM

THE LANCETLONDON: SATURDAY, NOVEMBER 16, 1940

EXTENSIVE experiments by mmseii and his collea-

gues on the transmission and infectivity of bacteria inair and in moist droplets led CARL FLUGGE (1847-1923)to promulgate the view that certain respiratoryinfections-he instanced diphtheria and whooping-cough-are contracted almost exclusively by intimateand immediate contact with droplets expelled by aninfective patient in talking, coughing or sneezing.He believed that the effective range of these dropletsafter coughing was not more than three or four feet,so that, for example, a susceptible person would haveto remain for 24 hours within four feet of a tuberculous

patient if he was to run any appreciable risk of becom-ing infected. He did not, however, deny that otherinfections, such as the acute exanthemata, might bespread to a distance by air-borne dried particles.Unfortunately present-day practice often uses " drop-let infection " and " air-borne infection " as synony-mous terms, but if progress is to be made in the

prevention of respiratory infections it is essential thatthe differences between these two methods of spreadshould be clearly understood and defined, even if thereis an ill-defined borderline. Droplet infection, in thesense that FLUGGE used it, is the direct spread ofinfection by moist droplets to persons within a radiusof three to four feet, while air-borne infection includesthe transmission of infection to greater distanceseither by very fine droplets which remain suspended inthe air to be carried hither and thither by air-currents,or by dried infected dust-particles raised into the airand similarly transported. Thus, droplet infection

might be likened to rain falling through the air, andair-borne infection to mist suspended in it. It wouldperhaps make for clarity if the former were called’’ projectile " and the latter " floating " infection.Droplets expelled in talking, coughing and sneezing

are obviously not all of uniform size ; there are

coarse droplets that fall quickly to the ground to infectthe dust, and these are probably seldom responsiblefor the direct spread of infection ; the majority aresmaller—1 mm. or less in diameter-which can beinhaled, and infect directly ; and there are droplets0-11-L or less across which according to WELLS are sosmall or quickly become so by evaporation that theyremain suspended in the air like smoke, the so-calleddroplet-nuclei. The part which these droplet-nucleiplay in initiating infection will depend on their

viability in air, on the infective dose of the bacteriumor virus contained in them, and thus indirectly on theirtotal number in the air. To take concrete examples,chicken-pox is certainly spread by droplet-nuclei,and, because the infective dose of the causal virus isvery small, the concentration required to initiateinfection is also very low. On the other hand, there isno direct evidence that scarlet fever or diphtheria canbe spread by droplet-nuclei although their materiesmorbi is often air-borne in dust-particles, but if

droplet-nuclei do play a part in the transmission ofthese infections a much higher concentration of them

would probably be required because of their lowinfectivity.

These considerations have an important bearing onany attempts to prevent respiratory infection. It hasbeen estimated! that the " muzzle velocity " of drop-lets expelled in a sneeze-and the camera has demon-strated conclusively that they come mostly through themouth, not the nose-is as great as 150 feet persecond, so that no physical or chemical aerial disin-fectant such as ultraviolet light or germicidal aerosolcan prevent projectile or direct droplet infection.Indeed, WELLS, WELLS and MUDD2 have suggestedthat the sneeze seems to be a provision of nature forthe survival of nasopharyngeal parasites. Obviously,only some system of masking can prevent dropletsbeing thrown out and the mask has already proved itsworth in the prevention of streptococcal puerperalsepsis, and, as some believe, in the control of influenza 3If the spread of infection in overcrowded shelters is,as seems likely, principally and primarily by droplets,then cheap and efficient masks will be needed, and,what is more important, the public must be educatedby propaganda to use them.

MISUSE OF TANNIC ACIDWHEN tannic acid was hailed a few years ago as the

perfect dressing for burns there seemed to be no pit-falls to avoid, no circumstances in which its use couldprove disastrous. Yet at a meeting of the RoyalSociety of Medicine last week (reported on p. 621) allspeakers agreed that tannic acid must never again beused for burns of the hands and face. The immediateresults of treatment may be good in some ways : the

coagulum protects the injured area, reduces exudation,and prevents sepsis, but it also produces grosscrippling of the hands, and by immobilising or

deforming the eyelids endangers the eyes. RearAdmiral C. P. G. WAKELEY, Mr. A. H. McINDOE andothers showed the evolution of these grave end-results by photographs. Tanning of third-degreeburns of the hands hinders the already impairedcirculation and leads to oedema which, by compressingthe vessels to the fingers, causes necrosis of the

phalanges. When healing finally occurs the mutilatedfingers are dragged backwards by scar tissue and auseless claw replaces what should have been a

functioning hand. The results of coagulation treat-ment on the face may be even more distressing. The

eyelids, fixed by horny tan, cannot be moved for amatter of days or weeks ; thus in the early stages adamaged eye may be out of reach of treatment, andin the late stages contractures and ectropion leave thecornea exposed to injury and infection which may evendestroy sight. These are disasters which must beavoided in future. Mr. McINDOE would have no

third-degree burn, whatever the site, treated bycoagulation. On the face and hands such burns mustbe treated by skin grafts as soon as the granulatingsurfaces can be suitably prepared. Elsewhere largedenuded areas, after saline-bath treatment, can

receive pinch or Thiersch grafts. Apart from baths,irrigation is being tried with saline containingelectrolytic hypochlorite, run into a Bunyan-Stannard oiled-silk envelope which encases the limb.1. Publ. Hlth Rep., Wash. July 19, 1940, p. 1315.2. Wells, W. F., Wells, M. W. and Mudd, S. (1939) Amer. J. pub.

Hlth, 29, 863.3. Sanderson-Wells, T. H. Times, Oct. 21, 1940.