H—3l

Study of Fig. II will show how difficult it is to be certain of the reality of the supposed relationship between these cases. The earliest illness noted was in Betty, sister of case B. If this had made her a carrier, she might possibly have infected Jerry Brown and case C as well as her sister (case B), and Jerry Brown might have conveyed the infection to the family of case A, who in turn might have passed it on to the family of case D ; but it is difficult to account for the discrepancies in time. Jerry Brown had left the case B home before he took ill on 14th September ; yet it was over two months before case B fell ill, and a similar interval separated Jerry's illness and the onset of case A. The more closely one studies it the more flimsy the whole structure appears.

Fig. II.—Possible Linkage Between Four Positive Cases and Sixteen other Suspicious Illnesses.

(Ages in brackets. Dates give time of onset. Unaffected members of households not shown.) 3—H 31

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