Recognition of historic influenza epidemics from parish burial records: a test of prediction from a new hypothesis of influenzal epidemiology.

On the current conception of the epidemiology of epidemic influenza, as caused by a mechanism of direct spread of the virus from the sick, epidemics must have travelled much more slowly in former times than at present. In contrast, a new hypothesis involving virus latency with seasonal reactivation predicts that in previous centuries influenza epidemics would have spread across the country at much the same speed as in the twentieth century. The study of burial registers in Gloucestershire parishes reported in this paper shows that lethal influenza epidemics at least as early as the sixteenth century can be recognized and dated as at present by the characteristic brief but large excess mortality that they cause. Examples are given showing that the character of the excess mortality caused by lethal influenza has not changed significantly over the centuries, a finding that supports the prediction of the new hypothesis but would not be expected on the current conception of influenzal epidemiology. In each century, influenzal excess mortalities in Gloucestershire parishes coincided with the date of the relevant influenza epidemic as recorded from widely different parts of Britain, thus further supporting the prediction of the new hypothesis as against current conceptions.