West Nile virus: Was diagnosed in the US due to the keen observations and persistence of a zoo veterinarian. Choices:

• A. Was diagnosed in the US due to the keen observations and persistence of a zoo veterinarian
• B. Was limited in its spread across the U.S. because rapid response and vector control measures were able to control it
• C. Was easily recognized when it entered the U.S. via monitoring programs conducted by public health and animal health officials
• D. Will likely be eradicated from North America within a few years

Answer: (A)

The key idea here is that veterinary observation can act as an early warning system for new zoonotic diseases. In 1999, an unusual pattern of bird deaths prompted a zoo veterinarian to investigate and persistently pursue samples for testing. Those efforts, followed by laboratory confirmation, identified West Nile virus as the cause in the United States. This story underscores how frontline veterinary clinicians can detect emerging threats and kick off the public health response that reveals a pathogen's presence in a new region.

The other statements don't fit the historical sequence as well. The diagnosis did not hinge on rapid vector-control success alone, nor did it arise simply from routine monitoring programs; the initial breakthrough came from the veterinarian’s keen observations and subsequent diagnostic confirmation. And West Nile virus has not been eradicated from North America and is not expected to be eradicated in the near future.