Terr10 is judged YES and the first incident satisfying Terr10 occurs east of 94 degrees west longitude (which is slightly to the west of Des Moines, Iowa).
If the "location" of the incident can not be determined (e.g., attack by a contagious infectious agent), then the location for the purpose of this claim will be "east" (as defined above) if it can be determined with reasonable statistical confidence that a majority of the deaths occurred in the east, "west" otherwise.
Clarification: The intent of this claim is that it directly depend on the outcome of Terr10 for determination of whether an incident qualifies. In the event Terr10 is judged YES, the judge of this claim should then decide on the location of the incident, not whether the Terr10 was judged "correctly." If Terr10 is judged NO, this claim should be judged NO. If Terr10 is not judged, this claim should not be judged.
I plan to judge this claim by its wording, not its intent.
For reference: Saint Paul, Des Moines, Jefferson City, Little Rock, and Baton Rouge are all EAST. Houston, Oklahoma City, Topeka, and Lincoln are all WEST.
If you are in doubt about a particular city, you can check its longitude at the USGS (link).