State health officials said the bubonic plague has been detected in animals in six Colorado counties, including in 10 cats that may have been infected through hunting and eating infected rodents. John Pape is an epidemiologist with the state health department. He said that cats present a concern because pets that become severely ill could transmit the disease directly to their owners. Dogs and cats also could bring infected fleas into the home. Counties that have detected the plague include Archuleta, Larimer, La Plata, Mesa, Montezuma and San Miguel. Bubonic plague was detected in animals throughout the state last year and in three humans. Since being first documented in Colorado in 1957, nine people have died from the plague.It usually takes from two to six days for plague to incubate, according to health officials. Typical symptoms include sudden onset of fever and chills, severe headache, muscle aches, nausea, vomiting and a general feeling of systemic illness. Lymph node pain and swelling is a suggestive symptom of bubonic plague.