Aerial infection

Abstract

On physical grounds there is no reason why human pathogens should not be carried over great distances and up to considerable heights; but as they have never been recovered from upper air or marine air the inferences are that they do not long survive exposure and that most human respiratory infections take place indoors. The theory of air-borne infection was practically abandoned for 40 years until Wells described droplet nuclei. The term “ aerial infection ” includes all modes of transmission in which the path of the infective agent lies through the air. Coughing, talking, or laughing contributes gentle bacterial showers to the air, but sneezing causes veritable intramural storms. Of the tens of thousands of droplets expelled from the mouth during a sneeze, about two-thirds remain air-borne. Only droplet nuclei and the finest dust particles are small enough to penetrate to the lungs. Contamination of air in overcrowded rooms cannot be effectively countered. Overcrowded public transport vehicles are the worst places for the interchange of nasopharyngeal flora; when housing is more closely linked with industry many such journeys will be unnecessary. The Ministry of Health’s campaign for respiratory hygiene has already influenced the amount of respiratory disease. Hospital blankets are an abomination and the results of oiling bedclothes and floors are not impressive. Air-conditioning does not ensure the degree of disinfection of the atmosphere which might be expected. The use of masks should be extended, but a comfortable and efficient mask has not yet been devised. Trials with germicidal ultra-violet radiation for air purification in children’s homes, nurseries, hospital wards, and operating theatres are impressive. The chief limitations of this radiation are its poor penetrating power and its ineffectiveness in the presence of dust. The new knowledge of the control of aerial infection should be incorporated in post-war rebuilding of hospitals. © 1945, British Medical Journal Publishing Group. All rights reserved.