Why can plague be difficult to diagnose from symptoms alone?

Plague can be difficult to diagnose from symptoms alone because its clinical manifestations often overlap with those of other febrile illnesses, such as tularemia, dengue, or pneumonia.1

While the disease presents in three primary forms—bubonic, pneumonic, and septicemic—the initial signs, including fever, chills, fatigue, and weakness, are non-specific and common to many infections. Even the characteristic buboes (swollen lymph nodes) associated with the bubonic form may not be immediately present or distinct enough to rule out other conditions without further investigation.12

Because of this symptomatic ambiguity, a definitive diagnosis requires laboratory confirmation to identify the bacterium Yersinia pestis in a patient's blood, lymph, or sputum. Clinicians typically combine a patient's symptom profile with a history of potential exposure to rodents or their fleas to guide the diagnostic process. Prompt identification is ethically imperative, as early antibiotic intervention is critical to protecting the patient's life and reducing the risk of fatality.132