In early spring 2009, the CDC reported several dozen cases of novel H1N1 influenza ("swine flu") in the United States. By the summer, the number of confirmed cases was reported as over 40,000 and it was spreading globally.
The pattern of novel H1N1 cases represents a(n) ____ disease.
A) epidemic
B) endemic
C) sporadic
D) pandemic
E) opportunistic
