Diagnosis

If your doctor suspects plague, he or she may look for the Yersinia pestis bacteria in samples taken from your:

• Buboes. If you have the swollen lymph nodes (buboes) typical of bubonic plague, your doctor may use a needle to take a fluid sample from them (aspiration).
• Blood. You'll generally have Yersinia pestis bacteria present in your bloodstream only if you have septicemic plague.
• Lungs. To check for pneumonic plague, your doctor will take mucus (sputum) or fluid from your airways using a thin, flexible tube inserted through your nose or mouth and down your throat (endoscopy).