How is plague diagnosed?

U.S. health-care providers should suspect plague in anyone with large, painful, very tender lymph gland accompanied by fever, extreme tiredness, and a history of exposure to possibly infected rodents and their fleas in the western United States. Plague should also be suspected in a person with plague symptoms plus a history of handling sick or dead cats, or wild animals such as rabbits.

Patients with suspected plague should be hospitalized, placed in isolation, have specimens obtained for plague diagnosis, and immediately treated. All suspected plague cases must also be reported to local and state health departments.

Ref: http://www.dhpe.org/infect/plague.html