Plague epizootics among susceptible species often cause extensive mortality, releasing fleas into the environment, and intensifying the potential for infections in humans through flea bites. Plague exposure also occurs through direct contact with infected animals. The bacteria can be transmitted through a break in the skin or through mucous membranes by handling infected animals or inhaling infectious droplets expelled by a coughing or sneezing cat. Human plague is relatively rare with only about 10-12 cases reported in the US annually. The last LAC case was in a veterinarian who developed pneumonic plague from an infected cat in 1984.
Most cases occur in summer months when exposure to fleas is greatest.
In California, sylvatic plague occurs in the foothills, plateaus, mountains and foggy coastal belt. Prevention of human plague in urban areas is aimed at controlling rodents and their fleas by suppressing rodent populations around homes and minimizing pet contact with rodents and their fleas. In humans, the initial signs and symptoms may be nonspecific, including fever, chills, malaise, myalgia, nausea, prostration, sore throat and headache. Commonly lymphadenitis develops in those lymph nodes that drain the site of the flea bite, most often in the inguinal region. Both of these forms of plague are fatal if untreated.