Plague

CLINICAL FEATURES

• Bubonic plague: enlarged, tender lymph nodes, fever, chills and prostration
• Septicemic plague: fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organs
• Pneumonic plague: fever, chills, cough and difficulty breathing; rapid shock and death if not treated early

AETIOLOGIC AGENT

• Yersinia pestis - bacillus

INCIDENCE

• In the U.S., 1 to 40 cases reported annually (avg = 13 cases) by western states, 1971-1995
• Worldwide, 2861 cases reported by 10 countries to WHO in 1995

SEQUELAE

• Rare, consequences of disseminated intravascular coagulation, lung damage
• Mortality 50-90% if untreated; 15% when diagnosed and treated

COSTS

• Not known

TRANSMISSION

• Flea-borne, from infected rodents to humans
• Direct contact with infected tissues or fluids from handling sick or dead animals
• Respiratory droplets from cats and humans with pneumonic plague

RESERVOIRS

• Primarily wild rodents in U.S. (especially rock squirrels, ground squirrels, prairie dogs, other burrowing rodents)
• Commensal rats may be important elsewhere

RISK GROUPS

• In the U.S., persons exposed to rodent fleas, wild rodents, or other susceptible animals in enzootic areas of western states
• Most cases occur in southwestern states of NM, AZ, CO, and in CA
• Highest rates in Native Americans, especially Navajos; other risk groups: hunters; veterinarians and pet owners handling infected cats; campers or hikers entering areas with outbreaks of animal plague

SURVEILLANCE

• National Notifiable Disease Surveillance System (NNDSS) for animal plague surveillance, for reports of human cases, and laboratory testing of fleas, animal tissues and serum specimens, and serosurveys of carnivores
• CDC, Fort Collins, is a WHO Collaborating Center for Reference and Research on Plague Control, and reports all human plague cases in the U.S. to WHO

OPPORTUNITIES

• Increased self-sufficiency of state and county public health labs
• Expanded active surveillance through carnivore serosurveys and application of geographic information systems (GIS) to surveillance programs
• Increased education of public and health professionals
• Collaborative applied research on plague prevention and control with other federal, state, and local health agencies, including application of GIS to surveillance

RESEARCH

• Ecology-based prevention and control strategies
• Improved diagnostic reagents and methods
• Risk factor identification using landscape ecology and epidemiology