"Plague" - what is it, definition of the term
Plague is a zoonotic bacterial infection caused by Yersinia pestis, historically responsible for widespread pandemics; the pathogen persists in wild rodent reservoirs—particularly rats and mice—and reaches humans chiefly via the bite of infected fleas or direct exposure to contaminated animal tissue.
Detailed information
Rats and mice serve as primary reservoirs for the bacterial disease caused by Yersinia pestis. The pathogen multiplies within the lymphatic system of these rodents, producing a high concentration of bacteria in their blood. Fleas that feed on infected rodents acquire the bacteria and become vectors, transmitting the infection to humans and other mammals during subsequent blood meals.
Transmission to humans occurs mainly through three pathways:
- Bite of an infected flea, introducing bacteria directly into the bloodstream.
- Contact with contaminated animal tissue, leading to skin lesions that develop into swollen lymph nodes.
- Inhalation of aerosolized droplets from infected respiratory secretions, resulting in a severe pulmonary form.
Clinical manifestations vary by route of entry. Bubonic presentation features painful, enlarged lymph nodes, fever, and chills. Septicemic progression includes rapid onset of shock, disseminated intravascular coagulation, and high mortality without prompt therapy. Pneumonic involvement produces cough, hemoptysis, and can spread person‑to‑person via respiratory droplets.
Mortality rates historically reached 60–90 % in untreated cases. Antibiotic regimens—streptomycin, doxycycline, or gentamicin—reduce fatality to under 10 % when administered early. Preventive measures focus on rodent control, flea eradication, and surveillance of wildlife populations. Effective strategies combine baited traps, environmental sanitation, and insecticide application to break the rodent‑flea‑human transmission cycle.
Outbreaks have shaped demographic and economic patterns across centuries. Urban centers with dense rodent populations experienced rapid spread, while rural regions suffered prolonged endemic transmission. Modern public‑health infrastructure monitors rodent density, conducts rapid diagnostic testing, and implements quarantine protocols to limit resurgence.