Spread of influenza in a factory.

It is generally agreed that colds, influenza, and other respiratory ailments are among the principal causes of sickness absence in industry, and that some of this absence results from cross-infection between fellow-workers. The total working days lost far exceeds those lost for other reasons, such as industrial disputes, yet com paratively little study has been devoted to the subject of infection in factories. Experiments with ventilation equipment, ultra-violet irradiation, etc., are considered too costly, too time-consuming, or too difficult to assess. Thus the factors which favour or restrict infection at work are not precisely known. In theory, it should be possible to learn a great deal from statistics of sickness absence. In practice, sickness absence rates are so profoundly influenced by the age and sex of the workers and the season of the year that valid comparisons between departments or factories require more elaborate standardization than existing records allow. An even more serious defect is that the records rarely include sufficient data about such conditions of work as are likely to affect morbidity. The difficulty of standardization can be by-passed in a study restricted to rates of absence from influenza, since this disease does not discriminate between men and women, affects all age-groups, and tends to occur in relatively short and well-defined epidemics. If the records also include a nucleus of environmental data, some of the laws governing cross-infection at work may be elucidated. This paper describes the use made of an opportunity provided by the 1951 influenza epidemic. The material collected was too slight to support any original methods of analysis, but it did provide an interesting sequel to a previous study of the spread of tuberculosis in factories (Hewitt and Stewart, 1951). Material