Certain Aspects of Acute Infection of the Respiratory Tract

Many years have passed since Flugge first drew attention to the probable importance, in the transmission of infection by way of the respiratory tract, of material expelled into air by infected individuals during the acts of talking, coughing, or sneezing. Infective particles disseminated in this manner manifest themselves in two forms: the moist state, in which many of the particles are relatively heavy and settle rather rapidly a short distance from the point of origin; and the very small particles which dry quickly and remain suspended in the air for variable periods of time, the so-called droplet nuclei. The former may rise again into the air in the form of dust resulting from the disturbance, by one means or another, of the surfaces upon which they rest. Viability and infectivity of the microbiological agents contained within the dried material are of variable duration, depending upon a number of environmental conditions. Distribution is easily promoted by air currents and the infectious material may travel considerable distances. Another probable and important mechanism of transmission of infection of the respiratory tract is by direct contamination of articles of common use, the handling or use of which may permit infectious material to establish contact with the upper respiratory tract. A striking example of this is the heavy contamination by infective agents of such articles as blankets, which, on being moved or shaken, disperse in the living state large numbers of the organisms with which they are contaminated. The chief portal of entry of infectious microorganisms into the human body has at all times been the respiratory tract. This is readily understandable if we bear in mind that this physiological system is continuously open to all floating matter in the air. That it is partially protected by sticky, mucous membranes lining tortuous passages, by aggregation of lymphatic tissue; by ciliary movement along tracheal and bronchial mucosae is true; but one has only to examine the lungs and regional lymph nodes to discover how much foreign material penetrates the protective barriers and reaches the deeper tissues. Unfortunately, infection of the respiratory apparatus is spread, for the most part, directly from individual to individual by the necessary and continuous association of human life. At present there is no discernible