A woman is in stable condition with bubonic plague, the first confirmed human case in Los Angeles County since 1984, health officials said Tuesday.

The woman, who was not identified, was admitted to a hospital April 13 with a fever, swollen lymph nodes and other symptoms. A blood test confirmed the bacterial disease, and she was given antibiotics, officials said.

Bubonic plague is not contagious, but if left untreated it can morph into pneumonic plague, which is. Bubonic plague is usually transmitted to humans from the bites of fleas infected by rodents.

Health officials said they suspect the woman was exposed by fleas in her home and that there was no cause for alarm. An estimated 10 to 20 Americans contract plague each year, mostly in rural communities.

Bubonic plague is believed to have been the "Black Death" that killed 25 million people in Europe between 1346 and 1351.