infectious diseases
Plague and Other Yersinia Infections
Introduction
Plague is caused by the gram-negative bacteriumYersinia pestis. Symptoms are either severe pneumonia or large, tender lymphadenopathy with high fever, often progressing to septicemia. Diagnosis is epidemiologic and clinical, confirmed by culture and serologic testing. Treatment is withstreptomycinorgentamicin; alternatives are a fluoroquinolone ordoxycycline. Yersinia(formerlyPasteurella)pestisis a short bacillus that often shows bipolar staining (especially with Giemsa stain) and may resemble a safety pin. Massive human epidemics (eg, the Black Death of the Middle Ages, an epidemic in Manchuria in 1911) have occurred. More recently, plague has occurred sporadically or in limited outbreaks. In the US, the last urban outbreak of rat-associated plague occurred in Los Angeles in 1924 to 1925. Since that time,>90% of human plague in the US has occurred in rural or semirural areas of the Southwest, especially New Mexico, Arizona, California, and Colorado. Worldwide, most cases since the 1990s have occurred in Africa; the Democratic Republic of Congo and Madagascar are most endemic. Peru is also one of the most endemic countries. In the last 20 years, almost all of the cases occurred among people living in small towns and villages or agricultural areas rather than in larger towns and cities. 