In two communities of similar size and age structure (A and B), there were outbreaks of viral illnesses (virus A in community A, and virus B in community B), both of which were traced back to a single source. Exposure to these viruses in each community confers permanent immunity. In community A, 200 susceptible people were exposed to an index case, 150 people were infected (not including the index case), 75 people became ill, and 40 people died. In community B, pathogenicity was 40%, infectivity was 90%, and virulence was 60%. Which virus had the greatest infectivity?

Question

Quizplus · Accepted Answer

Infectivity is the proportion of susceptible individuals who become infected after exposure to a pathogen. In community B, 90% of susceptible individuals were infected, while in community A, only 75% of susceptible individuals were infected. Therefore, virus B had the greater infectivity.

In Two Communities of Similar Size and Age Structure (A