POLIOMYELITIS (Infantile Paralysis)

Although paralytic poliomyelitis (the " major " illness) is the overt form of illness following infection with the specific virus, it is produced in a minority of those infected. In a far greater proportion there is either no manifestation of illness or there is a disturbance of varying clinical severity unaccompanied by paralysis. There is no doubt that in some of these " minor " illnesses the virus actually reaches the central nervous system but the illness aborts without sub­sequent paralysis. That a considerable amount of unrecognized infection occurs in the community can now be demonstrated by the virologist who is able to show the presence of serum antibodies (a sound index of past infection) in a high proportion of the adult population—often, indeed, in people who are unaware of having encountered the infection.

The virus enters the body by the mouth, multiplies in the cells of the intestinal mucosa, and is excreted in the faeces. The central nervous system is reached by way of the blood stream so that virasmia precedes the onset of clinical evidence of involvement of nerve cells. The infectivity varies greatly, but it would appear that the fsecal excretion of virus is greatest in the most severe cases. Virus is present in the stool of all paralytic cases, the excretion slowly waning over a period of eight to ten weeks. In about half the patients, stool cultures become negative in three to four weeks.Poliomyelitis is a notifiable disease. There are three serological types of poliomyelitis virus, of which Types i and 2 seem to be the more frequent epidemic producers. The incubation period probably varies widely although in most cases it lies between seven and ten days Prevention and Epidemiological Control.—Specific Prophylaxis.—The known presence of antibody in the serum of many adults encouraged the use of gamma-globulin to confer a temporary passive immunity and thus to prevent the disease in contacts along lines exactly similar to those which proved successful in measles. Although theoretically sound, it is not a practicable method of control and its use is not advocated.
Two varieties of polio vaccine are available:
(1) The first (Salk-type) consists of formalin-killed viruses of the three antigenic types. This material is injected intramuscularly or sub-cutaneously in doses of i -o ml. The first two injections are given with an interval of four weeks ; a third dose after a period of six months is an essential part of the immunization programme and, indeed, it is desirable to give a fourth injection a year or two later. The vaccines which are now available have undergone careful safety tests ; they contain an increased quantity of antigen, and are very effective in inducing a measurable humoral immunity. The widespread use of Salk-type vaccine has been responsible for a sharp decline in the incidence of poliomyelitis in the United States and Britain.
(2) The second (Sabin-type) vaccine consists of live attenuated polioviruses. It may be obtained in monotypic form (most commonly used in North America) or in tri-typic form (mainly used in this country). This vaccine is easily administered : the dose is dropped on a lump of sugar or similar vehicle which is then taken by mouth. The live virus infects the cells of the gastro-intestinal tract so that it is excreted in the stool for a considerable time after administration. Subsequently antibodies can be demonstrated in the serum.Appraisal of the Two Vaccines.—Both vaccines, in their present form, offer satisfactory immunity. With the killed virus vaccine this immunity is purely a humoral one so that, although poliovirus is prevented from reaching the central nervous system, intestinal infection can still occur. This can constitute a disadvantage to the older contacts of vaccinated children since unsuspected infection of the vaccinated might enhance the exposure of the unvaccinated. Further, with the passage of time, immunity might be expected to wane in the older person, who would, however, be less inclined to present himself for " booster " injections. Finally, there is the slight inconvenience involved in its intramuscular injection.
The live attenuated virus vaccine is free from most of these disadvantages. The simplicity of its administration has meant that large townships have been immunized in a carefully organized, one-day programme. In the face of a rising incidence of the disease this could permit the application of the vaccine very rapidly—preferably using a monotypic vaccine of a type not causing the epidemic —and indeed this method would seem to have been successful in halting the progress of an epidemic. It may be that in such conditions an " interference phenomenon " comes into plav; the bowel cells become infected with the " tamed " strain and prevent the " wild " virus from successfully colonizing them.

The fear of " antigenic shift "—the mutation of low virulence to higher virulence strains during intestinal passage—would not, in the event, seem to have been of practical significance. There is some evidence that minor antigenic change occurs but, having regard to the very large populations that have been successfully vaccinated, there has been no indication of harmful effect. Some cases of paralysis have occurred in vaccinated subjects, usually in adults, which could possibly be attributed to the administered virus. Such events, however, have been of the order of one in several millions vaccinated and absolute proof that the vaccine virus was responsible has often been lacking.
There probably exists a place for both vaccines. If the '' quadruple vaccine " (diphtheria, tetanus, pertussis and killed poliovirus combined) could be produced free from side-effects, there would be much to be said in its favour. It would, however, be unlikely to contribute to the eradication of the disease. There is ground for believing that a really intensive world-wide campaign, using the live attenuated vaccine, would be likely to interfere seriously with the natural history of the virulent poliovirus. The vaccine of choice, therefore, is that of the live attenuated form—preferably administered on a widespread scale during the non-polio season of the year.
General Measures.—By the time that a diagnosis of paralytic poliomyelitis is made it may be assumed that infection has been well distributed among the immediate contacts. This makes effective control very difficult. There is, how­ever, agreement that the patient must be promptly and effectively isolated and this is best done by admission to an infectious diseases hospital. Children who have been in contact with the patient should be kept under strict medical surveillance for a period of three weeks from the date of last contact. Adult contacts may continue their occupation providing it does not entail mixing with children, as in the case of nurses and school-teachers. They should, however, abstain from all social activities for three weeks from the date of last contact; kissing or playing with. young children must be strictly forbidden.
Any form of strenuous activity should be avoided. A contact who suffers from a febrile illness or who complains of any symptoms suggestive of an abortive attack of poliomyelitis should be strictly isolated until recovery ensues. Bed rest should be insisted on for a period of at least one week. During epidemics the practitioner should advise mothers to ensure that children are not over-active and that they secure adequate rest. A short period of enforced rest immediately after the midday meal is a sensible measure.
It is now accepted that certain factors provoke and determine the nature of the predominant paralysis. For example, tonsillectomy may be followed by a severe form of bulbar infection. During periods of prevalence opera­tions on the nose and throat should not be undertaken. Intramuscular injections may be followed by considerable local reaction and this has been associated with paralysis in the limb used for the injection. Alum-containing vaccines have been especially incriminated and for this reason immunization programmes are often temporarily suspended during periods of increased prevalence. This risk should be eliminated by ensuring that polio vaccination is carried out early in life and immunity maintained by " booster " doses. Pregnancy renders women more vulnerable to infection by poliomyelitis, and therefore in the care of the expectant mother immunization with killed vaccine is desirable. Finally excessive mus­cular activity during the period when the person is infected with the virus may contribute to the development of severe paralysis. Hence, during periods of increased poliomyelitis prevalence additional caution is justified in the treat­ment of any unexplained febrile illnesses, for these may be in fact minor reactions to polio virus infection. After recovery from such illnesses energetic sports should be forbidden for a week or two.
Curative Treatment.—Serum Treatment.—Neither convalescent serum nor gamma-globulin has effect upon the course of poliomyelitis, for by the time a diagnosis has been made the virus is in the nerve cells and beyond the reach of antibody.
General Management.—The " Minor " Illness.—It is easy to seem over-fearful of poliomyelitis, but there is no doubt that few infections rouse such strong emotional reactions in parents. Since the symptoms of the minor illness are vague and non-specific—fever, headache, vomiting or nausea, pain in the back, stiffness of the neck, drowsiness or irritability with, in the more severe forms, muscular pains or weakness—the condition will only be recognized when there is either a history of contact with a case of paralytic illness or when the disease is known to be present in the district. In such circumstances it is wise to adopt caution in dealing with minor febrile illnesses and to counsel complete rest. It seems possible that strict bed rest in such cases may minimize, though it will not always completely prevent, subsequent paralysis.
The " Major " Illness.—This may be suspected when there is extreme irritability, muscle tenderness or pain or obvious paralysis. Spinal and neck stiffness is usual in these cases : hence the patient either cannot sit up, or when he does so cannot bend forward to make the chin touch the knees. Unnecessarily " finicky " examinations should be avoided ; careful observation will permit accurate diagnosis and the full assessment of paralysis can await the disappear­ance of muscle pain and tenderness. This pain and tenderness can be most commanding and may be relieved by continuous hot flannel packs. The affected limbs should be placed in a position of rest by means of properly placed pillows and sandbags and by the use of a " cage " to take the weight of bedclothes. When the patient is being treated outside of hospital, the advice of an ortho-pasdic surgeon should be immediately obtained.
When the shoulder-girdle muscles are involved, the possibility of inter­ference with respiratory efficiency must always be kept in mind. Careful examination to exclude diaphragmatic paralysis must be made. The patient should be asked to count from one upwards to see how far he can get with a single breath. The test can be frequently repeated and forms a useful gauge of diminishing respiratory control. It is important to differentiate between respiratory insufficiency due to lack of muscle power in diaphragm and inter-costals from that due to obstruction of the airways by mucoid secretions from loss of the power of swallowing. These latter cases—the true " bulbar " forms— often present as respiratory infections or pneumonia, and their early recognition is of great importance. Here the immediate need is the establishment of adequate drainage, which is best obtained in the prone position with the foot of the bed raised. Suction of the pharyngeal secretions must be frequently carried out and every care taken to ensure a clear airway. Contrary to the common belief, these purely bulbar cases, when properly managed, will usually recover; the patient who is in greatest danger is the one in whom there is a combination of spinal and bulbar involvement, when the most skilled medical and nursing care is essential. All preparations must be made to maintain respiration (p. 688).
When all muscle tenderness has disappeared, simple splints (e.g. Cramer wire) should be applied under the guidance of an orthopsedic surgeon, who should, in fact, be called upon to assist in the supervision of the patient from the onset of paralysis. The limb should never be encased in plaster but should lie in plaster " shells " or padded Cramer wire splints made to the individual's requirements so that daily gentle massage and passive movements of the affected limbs may be supplemented by the local application of hot packs. There is a good deal to be said for the institution of fairly vigorous physiotherapy as soon as pain and tenderness have disappeared. After an isolation period of three weeks, arrangements should be made to secure continued orthopaedic super­vision and treatment, preferably by transfer of the patient to an orthopaedic hospital. It is important to see that those patients who have been regarded as " non-paralytic " are brought back for review three to six months later. Minor degrees of paralysis—especially of spinal muscles—may easily be overlooked during the acute stage.
The early period of the major illness is often regarded as a time when there is " nothing to be done ". This is not the case. As soon as tenderness is gone, movement should be begun—passive if the muscle group is powerless but with assistance against gravity where minimal contraction is present. Movement under water requires less muscle power and can be started early. The patient may be trained in simple muscle contractions which will enhance the chance of recovery. In other words, activity should be encouraged as soon as freedom from discomfort permits.