【单选题】Although genetic mutations in bacteria and viruses can lead to epidemics, some epidemics are caused by bacteria and viruses that have undergone no significant genetic change. In analyzing the latter, ...
A.
An outbreak of Lyme disease
B.
An outbreak of dengue hemorrhagic fever
C.
An epidemic of typhoid
D.
An epidemic of paralytic polio among infants
E.
An epidemic of paralytic polio among adolescents and adults