The public and domestic domains in the transmission of disease

Abstract

SummaryThis paper discusses the distinction between the transmission of infectious diseases within the domestic domain (the area normally occupied by and under the control of a household) and that in the public domain, which includes public places of work, schooling, commerce and recreation as well as the streets and fields. Whereas transmission in the public domain can allow a single case to cause a large epidemic, transmission in the domestic domain is less dramatic and often ignored, although it may account for a substantial number of cases. Statistical methods are available to estimate the relative importance of the two. To control transmission in the public domain, intervention by public authorities is likely to be required. Two examples show how environmental interventions for disease control tend to address transmission in one or the other domain; interventions are needed in both domains in order to interrupt transmission. More than 20 years ago, Bradley and colleagues proposed the classification of water-related infections according to their mode of transmission, rather than the type of organism which caused them or their effect on the patient (White et al. 1972). This classification into water-borne, water-washed, water-based and water-related insect vector groups was a new paradigm which has stood the test of time with only a few modifications, and greatly helped to clarify our thinking about how environmental interventions such as water supply improvements affect disease. It has three advantages. First, it was so simple and (in retrospect) obvious that it was hard to argue with it or forget it. Second, it built on existing knowledge, and drew together the conclusions of a number of studies and authors in widely differing environments.Third, it helped to clarify the issues for the practitioner.The one significant improvement, made to the Bradley classification by Richard Feachem (rq77), was to consider it as a classification of transmission routes rather than of diseases, because (as Bradley had recognized) some diseases could be transmitted by more than one route. This helped to redouble the interest in the transmission process, which is the particular concern of those of us who seek to control disease by environmental modification rather than by immunization or the treatment of patients.We propose another division of transmission routes which cuts across the preceding categories and is complementary to that classification. It is not limited to the water related diseases and can apply to all infections. Our division is between transmission occurring within the domestic domain-the 27( j I996 Blackwell Science Ltd

The epidemiology of hepatitis A in Rio de Janeiro: environmental and domestic risk factors

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