Family studies of respiratory infections

Abstract

A clinical and bacteriological study of respiratory illness was carried out in families of the same size and structure (two parents and three children) living in various types of house in a working-class area of London. The study, which lasted two years, included regular visits by a paediatrician or nurse, who, besides making clinical and social observations, took fortnightly throat and pernasal swabs from all members of the family. Observations on the spread of “ indicator ” organisms within the family groups were used to confirm or modify the epidemiological indications about the introduction and spread of infection given by traditional clinical methods. Of some twelve social and environmental factors examined—for example, maternal care, range of outside contacts, and dampness of the house—only overcrowding and, with less certainty, inadequate clothing were found to be related to the incidence of acute coryza and chronic catarrh. The increased clinical secondary attack rate in conditions of continued close contact observed in the more crowded families was confirmed by the higher rate of apparent transfer of type-specific pneumococci in these families. On clinical grounds alone, infections appeared to be most often introduced by the youngest or pre-school child—that is, the most susceptible member of the family. Corrections for differences in susceptibility gave results which suggested that even in congested working-class districts the school child is the most frequently exposed to extrafamilial infection and the most vigorous spreader of infection within the family. The greater frequency of transfer of pneumococci and the higher carrier rates of haemolytic streptococci among the schoolchildren supported this conclusion. Pneumococcus carrier rates were raised following the onset of acute coryza, but there was no evidence that the pneumococci were causally related. Climatic changes appear to affect both the frequency of introduction of colds into households and the ease of transfer ; our own findings and those of other workers suggest that this association is at least partly due to changes in host susceptibility following abrupt seasonal changes in temperature and other climatic factors. Undue susceptibility to colds was shown to be a characteristic of individual children but not of families as a whole. Although some differentiation of syndromes presenting as “ acute coryza ” and “ sore throat ” was possible on epidemiological ground, sore throats often occurred without the presence of haemolytic streptococci in members of the family, and it seems likely that this syndrome results from more than one type of infection. A comparison of the experience of tonsillectomized and other children showed that, although streptococci were found less often in the throats of the tonsillectomized children, the incidence of coryza and sore throats was identical in the two groups. © 1958, British Medical Journal Publishing Group. All rights reserved.