Armstrong – Table of Contents

Various parties and social gatherings occurred during the epidemic attended by variable
numbers of persons some of who attended more than one gathering. The largest was on
January 29 when 30 people attended a masquerade dance. The attack rate in this group
was 77 per cent. The authors were uncertain about the contribution of these gatherings to
the attack rates since many of the attendees at these events were exposed to multiple
potential sources of infection in the community.
The authors evaluated other possible sources or factors contributing to the spread of the
infection including milk, water, insects, crowding, economic status, housing conditions,
and general sanitation. These factors did not appear to influence the acquisition of illness.
A factor that they thought did influence the incidence of infection was immunity acquired
during the earlier epidemic of 1918. Of the 136 cases who were ill in 1918, there were 27
re-attacked in 1920, or an attack rate of 19.8 per cent for this group; this contrasts with an
attack rate of 62.4 per cent in the group of population not affected in 1918. The authors
postulated that this difference indicated the presence of a relative but not absolute
immunity some 15 months following the previous infection. They cited other studies in
the published medical literature (11) that demonstrated similar findings.
After tabulating the detailed data on the population of 689 persons present on Kelleys
Island during the 1920 influenza epidemic, the authors provided the following summary:
1). The public school, which remained in session without medical supervision of any kind
during the early portion of the 1920 epidemic, served as a center for the spread of
influenza upon the island. They did not mean to infer that prompt closure of this school
would have prevented the 1920 epidemic, but it did seem probable that it would have
delayed it.