Plague is a disease of rodents and their fleas that can be transmitted to humans. Throughout history, plague, often referred to as the "Black Death," has caused catastrophic pandemics resulting in deaths of tens of millions of persons. The disease is caused by a gram-negative bacterium, Yersinia pestis. Humans are usually infected by the bite of infective rodent fleas, but infection also occurs through handling or ingesting infectious animals or by inhaling infective respiratory droplets expelled by humans or animals.
Initial signs and symptoms of plague may be nonspecific, with fever, chills, headache, malaise, musculoskeletal pains, nausea, and weakness leading to prostration. Persons with bubonic plague, the most common form of plague, typically develop painful, swollen lymph nodes near the site of an infective flea bite. Less common forms of plague can infect the bloodstream (septicemic plague),
In any of its clinical forms, plague can be fatal if not diagnosed and treated correctly early in the course of the disease. The diagnosis is made by combining information on possible infective exposures, clinical signs and symptoms, and results from laboratory tests. Treatment, which should begin as soon as the diagnosis is suspected, relies on the aminoglycoside group of antibiotics (streptomycin, gentamicin), tetracyclines (doxycycline, tetracycline, oxytetracycline), chloramphenicol, or trimethoprim-sulfamethoxazole. Laboratory diagnosis is made by direct examination of stained clinical materials, serologies, antigen-detection, isolation of culture media, and molecular-genetic characterizations.
Plague is present in wild rodent populations over large but scattered rural areas of the Americas, Africa, and Asia. Outbreaks sometimes occur among wild rodent populations and occasionally among rat populations in villages and towns, though rarely in cities. When plague involves rats living in or around homes, humans are at their highest risk of exposure. In the United States, plague occurs in the western third of the country, most often in burrowing rodents and their fleas. Plague also occurs in scattered areas of South America, especially the Andean region; in north-central, eastern, and southern Africa; in Madagascar; in several states in the Near East (Saudi Arabia, Yemen, Jordan, and Iranian Kurdistan); central and southern Asia (Georgia, Kazakhstan, Mongolia, China, and India); and Southeast Asia (Myanmar, Vietnam, and Indonesia).
Plague prevention on an individual level involves avoidance of areas of known plague activity, taking personal precautions against flea bites, avoiding sick or dead animals, and seeking medical care at the earliest signs of illness. No vaccine against plague is available in the United States. Pneumonic plague patients should be managed in isolation under respiratory droplet precautions. Postexposure antibiotics may be warranted for persons who, in the previous two days, were likely to have been exposed to infectious fleas or have had close direct exposure to a person or animal with pneumonic plague. Routine community prevention and control of plague is achieved through sanitation and hygiene measures that limit food and harborage for rodents. In the event of a plague outbreak, flea control should be implemented before attempts are made to kill rats.
DAVID T. DENNIS
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