![]() ![]() The cough becomes increasingly productive, eventually yielding frothy, infectious, bright red sputum teeming with bacilli. They quickly advance to fever, cough and difficulty breathing. Symptoms begin with rigor, severe headache, nausea and malaise. Following an incubation period of 1-6 days, primary pneumonic plague develops very rapidly. pestis is even more virulent than that which ensues after fleabite. The course of plague in individiuals infected directly by airborne Y. Pneumonic plague allows for direct person-to-person transmission via infectious respiratory droplets. ![]() Occasionally, bubonic and septicemic infections progress to secondary pneumonic infections. Up to 30% of fleabites lead directly to sepsis, without prior evidence of a bubo. Without prompt antibiotic treatment, approximately 50% of bubonic plague cases progress to sepsis and death. The disease-defining symptom is the bubo, a painful swelling of the lymph nodes draining the fleabite. Humans are incidental victims in these deadly cycles.įlea-borne human infections usually cause bubonic plague. In endemic areas, plague epizootics periodically decimate susceptible rodent populations. pestis is also facilitated by the death of its mammalian hosts, which compels infected fleas to seek new hosts. pestis to achieve high titers within the mammalian bloodstream, thereby facilitating vector-borne transmission. ![]() Evolution selected for traits that enable Y. This Gram-negative, nonmotile bacterium evolved recently from Yersinia pseudotuberculosis, an enteropathogen. Yersinia pestis, the disease-causing agent, was first identified by Alexander Yersin in 1894. Plague is an exceptionally virulent, zoonotic infection transmitted naturally from rodent reservoirs to humans via fleas. ![]()
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