The initial signs of infection are fever, chills, malaise, nausea, prostration, sore throat, and headache.
Bubonic plague occurs when the infection primarily involves the human lymphatic system.
The lymph glands, particularly those in the groin, become swollen and tender. When the later occurs, the disease may be spread directly between people through an infected person coughing and sneezing. Occurrence Outbreaks of plague continue to occur in various parts of the world due to the maintenance of the bacteria among wild rodent populations such as ground squirrels. Areas infected with plague include the western United States, much of South America and Africa, central Asia and South-East Asia. No country officially requires vaccination against plague prior to entry.