INFANTILE PARALYSIS.

Hawera Star, Volume XLVIII, 6 March 1925, Page 6

INFANTILE PARALYSIS.

CAFSE AND MANNER OF ITS

SPREAD

The following circular lias been issued bv tlie Director-General of Health (Dr. T. H. A. Valin tine) and .is published i'or the information of the general public: — PRESENT KNOW f.EDGE.

Throughout the world from 1880 to the present day over 150 outbreaks oi infantile paralysis have been recorded. In 45 epiedmics which occurred before 1905 the average number of cases recorded was low, viz., 21. . Since then there has been a. marked increase both in the frequency of the epidemics _a-nci in the average, oi cases recorded m each. Over a quinquennial period the number of cases per epidemic now averages from 300 to 000, and as an exceptional instance New York City -reported 8928 cases in 1916. with 240/ deaths. ... This increase cannot be wholly accounted for by the fact that infantile paralysis is now better known and is therefore move readily recognised and diagnosed as such. „, _ „ , Wickman. of Sweden, in 1905-6 made the first systematic study of the disease from an epidemiological point of view, and found evidence that it was infections. He directed special attention to several factors in its spread viz., routes of travel, public gatherings of children, abortive or ambulant eases, and healthy intermediate carriers. I'n 1909 the disease was experimentally conveyed to monkeys by inoculation from the spinal cord of a child ■who had died of the disease.

Since then leading scientists ana physicians in many countries have addecl considerably to our knowledge. The symptoms of the disease have been clearly described. Its pathology, thanks to, the monkey, is definitely known. As regards bacteriology, this disease has been definitely' shown to be one of those produced by organisms so minute that they will pass through the pores of the finest laboratory filter and remain invisible under ’the highest _ powered microscope available. In this respect it is on all fours with smallpox, measles, mumps, rabies, typhus, anti yellow fever, which have been undei investigation for many years. Tt is true of infantile paralysis, as of some of these other “filter passers, 1 that by special culture visible and characteristic colonies or clumps ol the organism have been cultivated, and that bv repeated inoculation of a series of monkeys these clumps have been proved to contain the germ. Work on filter-passing organisms is an advanced branch of bacteriology. Eminent bacteriologists are working at it daily. Neither care nor expense has been spared. What we in New Zealand can do is' to provide a very small, reinforcement to the large and expensivelyequipped army already in the field in this branch of inquiry. The virus obtained from the spinal cord, brain, spleen, bonemarrow, etc., of fatal cases, or from the nose, mouth and bowel discharges of living cases, reproduces the disease when injected into the brain of higher apes. It has also thus been conveyed by swallowing and by application to the mucous membrane of the nose. This virus in the laboratory is readily killed by heat and by - weak disinfectants, particularly hydrogen peroxide in 1 per cent, solution and permanganate of potash (1 part to 500 of water), but it resists freezing and drying for long periods. ■ . Tfc has been proved that healthy associates of infantile paralysis cases occasionally harbour the virus in their Hoses and throats.

IMMUNITY

One attack of infantile paralysis confers a high degree of immunity. Monkeys who have recovered from the infection show a high degree of resistance in that they are not susceptible to infection by again inoculating them and their blood-serum, when mixed with the virus renders it harmless to other monkeys. ' It has also been shown recently that human blood serum from mild abor-tive-cases when mixed with the virus renders! it inert, just as does, the serum of typical cases in which paralysis. has developed.

MODES OF TRANSMISSION.

The modern explanation, of recurrent epidemics of infantile paralysis, and their distinctive features is that it is a very communicable disease like;'measles, and is much more widespread- in the community than,, would he indicated by paralytic cases alone., Most bases' are mild, escape notice, and leave, the individual. protected against further attacks. There is thus la. high degree oi acquired immunity except in the young. Only the occasional severe case with paralysis is recognised and diagnosed a.» infantile paralysis. • It is most infectious during the early stage of the disease. We are therefore deal • ing with ia. common, infection, always present in. the community, hut which in recent years and particularly in the late summer and autumn seasons has gained an, increased virulence. Per-, sos of five years and under contribute approximately 70 per cent, of the cases, and epidemics in, any one country tend to recur every three to five years., seemingly when, a- fresh supply oi susceptible children, is available. Persons under sixteen years contribute over 90 per cent, of the cases. There is much evidence to support the opinion. that the disease- both in its' mild and in. its severe form is directly transmissible. from person: to person. In addition; healthy carriers persons who have been; in contact! with a. case, can carry the virus in the mucous membrane of their noses and throats, without suffering any symptoms. These carriers, even if the infection they carry comes from a mild unrecognised case, may produce an, attack of severe type if they chance to convey the infection to a sufficiently susceptible person . The latest views of Ulexner and Am,oss are that the virus -is regularly present in the nose and throat in cases, mild or severe, of infantile paralysis in the first days of illness, and especially in fatal cases.; that it_ diminishes relatively quickly as the disease progresses, except in rare instances; and"that it is unusual for the carrier state to develop in a, piationt who has recovered.’ Hence the period of greatest infertivity is early in the disease.

CLIMATIC THEORY

Though infanthe paralysis is now universally recognised to be an infectious disease, and though the consensus of opinion, which every year is further .substantiated, a-scribes, its spread to contact direct or irifii.rg.ct, it has been thought by some that peculiar climatic conditions may predispose to the disease and determine an epidemic, the genu itself he ing widespread hi, non-epidemic times. The data collected for many epidemics, including a number of winter one®, do not support this idea. Epidemics have occurred under very variable weather conditions as regards humidity, . temperature, dustiness, rains..and snowfall, and wind. Again, in the late summer and early

autumn epidemics, which are admittedly the commonest, it has often been noted; that the radial' spread, of the disease does not correspond to any constant climate factor. The outbreak will, he subsiding in one locality at the same, time that it is advancing in, another. and still later spread to another even whom' all three places- are experiencing weather conditions which at anv one tune are practically identical. The disease appears to follow lines of transport rather than to correspond to any definite climatic factor. Epidemics of most infectious diseases have a seasonal incidence. In the Northern. Hemisphere this seasonal incidence over a long period of years has been accurately tabulated. In the Souitrlierii Hfemisipter-e the reverse months are chosen.—e.g., infantile paralysis favours January to March, diphtheria March to June, scarlet and typhoid fevers April and May, measles June to August, ami whooping-cough August to October. The reverse is true of the Northern Hemisphere. CONCLUSION. Now that the higher apes can readily he inoculated with the virus of this disease it is hoped that further research, may lead to the discovery of a practical test for the immediate laboratory diagnosis of all cases and carriers;. also a reliable test for distinguishing between susceptible and unsusceptible persons, and some means of readily conferring artificial immunity against infantile paralysis.