One of the most interesting of recent developments in the field of infectious diseases has been the demonstration of viruses as an important factor in the etiology of acute upper respiratory infections.
The common cold is really an acute catarrhal condition of the nose and throat which usually involves to some extent the accessory sinuses, constitutional symptoms being absent or slight. It is difficult to draw a sharp line between the common cold and so-called grippe. In fact it is doubtful whether any such differentiation should be attempted. Both the laity and physicians consider grippe as a cold with definite constitutional symptoms, such as fever, headache, and malaise.
Influenza represents the third degree of severity, and might be defined as an acute catarrhal infection of the upper respiratory tract, occurring in epidemics of varying extent and severity, characterized by rapid dissemination, high morbidity, sudden onset with fever, extreme prostration and aching together with leukopenia. The attack in influenza on the bronchial tree is more rapid and intense.
Recent knowledge on the subject reveals that the common cold and influenza are initiated by a filterable virus, but that most of the toxaemia, discomfort and complications are caused by the invasion of secondary pathogenic bacteria such as the pneumococcus, streptococcus, staphylococcus and influenza bacillus.
Since its discovery by Pfeiffer during the influenza epidemic of 1889-1890, the influenza bacillus has been regularly found in cases of rhinitis which is accompanied with influenza, while in common rhinitis generally it has not been demonstrated. Artificial infection of animals with in tracheal, intrapulmonary or intravenous innoculations has been unsuccessful.
During the epidemic of 1918-1919, Pfeiffers bacillus was held responsible for grave complications, such as pneumonia, meningitis and septicemia. The bacillus was found in 91 percent of specimens examined at the bedside. Examinations made after an interval of three hours revealed a 3 percent positive incidence, which fell to zero in twenty-four hours. During this epidemic the exclusive role of Pfeiffers bacillus was debated. Material taken from the mouth washings of five patients was passed through a Berkefeld filter, dried, pulverized and its freedom from pathogenic bacilli ascertained. Since inhalation of this material resulted in a typical mind influenza, a filterable virus was considered the causative factor in grippe.
In 1931, Shope of Princton, furnished definite proof that in hog influenza, a disease simulating the human type, the combined action of two factors, a filterable virus and a small bacillus resembling Pfeiffers, produced all the clinical and epidemiologic symptoms. The virus if isolated from the bacillus produces in pigs a very mild influenza; it is responsible for the contagiosity, the changes in blood serum and the immunity.
The bacillus if isolated from the virus, is not pathogenic for hogs, but when associated with the virus, causes a severe infection with complication. In 1933, the same symbiosis of filterable virus and bacillus was demonstrated for influenza in men, pigs, ferrets and mice. In men, transmission of the virus only, produces mild rhinitis but not the fully developed picture of grippe. In mice and ferrets typical influenza leading to bronchopneumonia could be produced by the virus only.
Eighty volunteers were examined in Leningrad in 1936; forty- two were infected with living Pfeiffers bacilli, by inhalation. The others received cultures of killed bacteria, material from mouth wash of infected patients, etc. Repeated bacteriologic examinations performed before and after the inhalations demonstrated that the influenza bacilli multiply abundantly in the mucosa of the nasal cavity and pharynx during the first five to ten days. The number of hemolytic streptococci and pneumococci, verified in several individuals, did not increase during the infection with the influenza bacillus.
It is therefore concluded that the clinical symptoms are to be attributed to the toxins of Pfeiffers bacillus only. Contrary to the typical leukopenia of epidemic influenza there was moderate leukocytosis in 60 percent of the cases. NOne of the forty-two patients developed complicating lesions, and while in free contact with other persons, no transmission of the disease was observed. Control studies with the isolated virus fully confirmed the fact that the observations made in hog influenza are valid for human influenza also.
Animal experiments have revealed the presence of at least three types of virus and the fact the serum from vaccinated animals and from animals as well as human recovering from the natural disease contain anti-viral neutralized bodies.
Study has revealed also that the influenza previously classified as as a single disease in reality consists of a number of clinically and epidemiologically separable entities. Stuart- Harris states that the sudden onset with the constitutional symptoms followed later by coryza, sore throat ad cough, are the outstanding characteristics of the virus disease. The typical facies is heavy and drowsy with drooping eyelids, glistening eyes, dusky facial flush and slightly cyanosed lips.
The temperature rises rapidly on the second day and may or may not be followed by a remission on the third day, but there is usually renewed pyrexia on the fourth day. This is called diphasic temperature. Bronchiolitis is a common later complication. IN the febrile catarrhs the onset is insidious, and respiratory symptoms or angina appear early. The general symptoms are inclined to be overshadowed by the local symptoms in the respiratory tracts. The fever has no characteristic course, and shows no tendency to become diphasic. The general aspect is that of a patient with a severe cold.
Experimental studies in the University o;f Pennsylvania have demonstrated the close relationship between all strains of human influenza virus s;o far isolated , these beings immunologically homologous. This knowledge was obtained by observation on the cross-immunity and cross-neutralizing with viruses isolated from different localities during the mild pandemic of influenza in 1936-1937.
A comparison with strain from previous years and from other parts of the world gives added confirmation of this relationship. Certain strains, however, do possess antigenic difference.
Magill and Francis recently; described cross immunization studies on sixteen strains of influenza virus which showed wide difference between strains. Most adults in England and America have in their blood serum protective antibodies for both swine and human viruses, but children under ten rarely have antibodies against the human virus. This suggests have the swine virus was formerly the common infective agent in humans. However, there is no direct evidence that the swine influenza virus is today capable of infecting man. Indeed evidence indicates that it does not infect man, because while influenza has has occurred annually since 1918, the serologic evidence suggests that the human prototype of swine influenza virus ceased infecting man generally about ten years ago.
The most apparent interpretation of these findings is that the swine virus represents a surviving form of an extinct or temporarily quiescent human influenza virus which has become so fixed in swine as to be no longer pathogenic for human beings. If this is the case, then the history that swine influenza appeared for the first time in human virus.
The experimental and historical facts seem best explained by the theory that the swine influenza virus represent a surviving form of the pandemic in man in 1918. On this basis then the presence in human sera of antibodies neutralizing swine virus would be considered to indicate that the donors of these sera had undergone immunizing exposures to , or infections with, an influenza is more than merely an interesting analogue of the human disease; it may actually bear a relationship to pandemic influenza.
Bacillus influenzae is a small gram negative, non-motile hemophilic bacillus, consistently found in the secretions of the respiratory tract in influenza. The only filterable bacillary organism at present deserving consideration is Bacterium pneumosintes, discovered by Olitsky and Gates in the nasopharyngeal secretions of patients during the epidemic of 1918-1919, 1920 and the 1921-1922 epidemic. By producing a leukopenia, especially of the lymphocytes, there is an increased susceptibility of the organism t secondary infections.
During the epidemic of the 90s the coal-tar products were used in great quantities. Since these substances tend to destroy red blood cells and as the disease has a similar tendency, the combined effect can lead to serious consequences. The pain in the bones at the beginning of influenza represents the effects of the disease on the blood -forming marrow of the flat bones, and the consequent blood deterioration predisposes to cardiac and other complications.
