Lesson 1: Introduction to Disease Transmission and Epidemiology

1-10

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1-10. MULTIPLE CAUSATION

The concept of multiple causation is analogous to that of the chain of disease transmission. Just as there are three links in the chain of disease transmission, there are also multiple causes of diseases rather than one simple cause for each disease. The various factors of host vulnerability, agent characteristics, mode of

transmission, and reservoirs of a disease introduce a number of possibilities to which the cause of a disease may be attributed. An exaggerated illustrative example of the multiple causation concepts is the case of a pedestrian who was hit by an automobile and was taken to a hospital, where he subsequently died. In the autopsy, the pathologist attributed death to a ruptured spleen. The surgeon, however, considered

the cause of death to be slow diagnosis in the emergency room, since the spleen could have been repaired had the diagnosis been made promptly enough. To the internist, the cause of death was shock.

The investigating policeman blamed the death on excessive speed on the part of the driver, while the driver claimed that the pedestrian was intoxicated and reacted improperly. Which diagnosis is correct? In all probability, there is some merit in each of the arguments. Here we see a typical case of multiple causation where each of the factors involved could have been the cause of death, and each contributed to the death. Conversely, if the proper action had been taken to prevent the occurrence of each of the events, death could have been prevented. Just as there were several opportunities to prevent death in the example cited here, the chain of disease transmission presents several opportunities to interrupt the continuity that is required in the transmission of a communicable disease.

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