NATURE 



129 



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The Influenza Problem. 



THE widespread recrudescence of influenza in 

 this country, although on a less fatal scale 

 and of a less virulent type than in the experience of 

 1918-19, is an unpleasant reminder of our present 

 helplessness in respect of this disease. Many 

 lumes have been written about it. The old Local 

 Government Board issued two reports by Dr. 

 Franklin Parsons, which summarised all we then 

 ew of the epidemic of 1890, and did much to 

 and our knowledge; and we have now before us 

 even more portly tome of nearly 600 pages upon 

 e subject, issued by the new Ministry of Health, 

 his report contains valuable historic material, an 

 dmirable clinical study of the disease, and sugges- 

 ve speculations on the statistical aspects of the 

 iroblem presented by it. These forcibly impress us 

 ith the imperfections of statistics dealing with alto- 

 ther imperfect material. But we cannot be said to 

 ve greater knowledge of the disease, from the point 

 view of preventive medicine, than when Dr. 

 arsons's reports were issued. This is no reflection 

 the Ministry of Health ; for in every civilised 

 untry investigators have similarly drawn a blank so 

 ar as guidance for the prevention of the disease is 

 icerned. 



We know certain elementary facts which, if they 

 could be universally applied in practice, would pre- 

 vent influenza from spreading ; for the disease is 

 infectious, and it is practicable to lessen the public 

 opportunities of infection by avoiding unnecessary 

 assemblies of people. But how can we avoid infec- 

 tion in social and business life, in view of the early 

 NO. 2727, VOL. 109] 



infectivity of the disease, the failure to recognise 

 mild attacks, and the short incubation period, 

 which multiplies centres of infection at a very rapid 

 rate? We commonly fail to prevent the spread of 

 ordinary catarrhs ; and this is an index of our incapa- 

 city or inertia in relation to the more serious disease. 



The mere enumeration of matters concerned with 

 influenza on which we are still ignorant is an almost 

 tedious task. Let us attempt it partially. We 

 know that at uncertain intervals influenza marches, 

 or rather flies, through the world, without any 

 known reason. The epidemics in this country of 

 1803, 1833, 1837-8, and of 1889-92, are well 

 known, but many occurred in previous centuries, 

 and some have even asserted that the sweating sick- 

 ness was a type of influenza. We know that when 

 influenza becomes epidemic it tends to recur in 

 secondary and tertiary waves, as in our recent ex- 

 perience. The present outbreak is the fourth since 

 1918. Dr. Brownlee has given interesting evidence 

 pointing to an appearance of law in the intervals 

 after which recurrences occur ; and we may hope to 

 hear more from him on this point, not only as regards 

 this country but also for other countries, as to 

 whether this law holds good internationally. 



Knowledge of the natural history of these out- 

 breaks may be expected eventually to give some clue 

 to prevention, though this is not yet visible. 

 But it is not known why influenza takes on a world- 

 wide march at irregular intervals. We may assume 

 that endemic influenzal infection of low viru- 

 lence and infectivity, for some unknown reason, 

 changes its biological characters, and that one or 

 both of these characteristics may become en- 

 hanced; but why? Attempts to associate pan- 

 demics with special meteorological conditions have 

 had little or no success; and we are little further 

 advanced than when Sydenham appealed to the 

 " epidemic constitution " of certain years. 



As an alternative to the acquirement of enhanced 

 biological properties by the contagion of influenza 

 may be cited the evidence of importation of infection 

 and the rapid spread of the disease from country 

 to country ; but this merely puts the practical diffi- 

 culty further back. Why this exceptional spread 

 from country to country, and why does not influenza 

 prevail, like measles, every second year in a given 

 urban community? 



Further light would be more easily obtainable if 

 we were certain that the Pfeiff"er bacillus is the true 

 causal agent of influenza ; it is not dispossessed from 

 this position, but the evidence of bacteriologists in 

 recent outbreaks has not strengthened its position; 

 i and although bacteriologists have isolated the 



