Colorado girl recovering from bubonic plague

The parents of 7-year-old Sierra Jane Downing thought she had the flu when she felt sick days after camping in southwest Colorado.

It wasn't until she had a seizure that her father knew something was seriously wrong and rushed her to a hospital in their town of Pagosa Springs. She had a 107-degree fever, and doctors were baffled by the cause.

"I didn't know what was going on. I just reacted," Sean Downing said. "I thought she died."

The Downings eventually learned their daughter was ill with one of the last things they would've thought: bubonic plague, a disease that wiped out one-third of Europe in the 14th century but is now exceedingly rare - it hasn't been confirmed in Colorado since 2006 - and treatable if caught early.

Federal health officials say they are aware of two other confirmed and one probable case of plague in the U.S. so far this year - an average year. The other confirmed cases were in New Mexico and Oregon, and the probable case also was in Oregon. None were fatal.

Plague is generally transmitted to humans through the bites of infected fleas but also can be transmitted by direct contact with infected animals, including rodents, rabbits and pets.

The Black Death: Bubonic Plague

In the early 1330s an outbreak of deadly bubonic plague occurred in China. The bubonic plague mainly affects rodents, but fleas can transmit the disease to people. Once people are infected, they infect others very rapidly. Plague causes fever and a painful swelling of the lymph glands called buboes, which is how it gets its name. The disease also causes spots on the skin that are red at first and then turn black.

Since China was one of the busiest of the world's trading nations, it was only a matter of time before the outbreak of plague in China spread to western Asia and Europe. In October of 1347, several Italian merchant ships returned from a trip to the Black Sea, one of the key links in trade with China. When the ships docked in Sicily, many of those on board were already dying of plague. Within days the disease spread to the city and the surrounding countryside. An eyewitness tells what happened:

"Realizing what a deadly disaster had come to them, the people quickly drove the Italians from their city. But the disease remained, and soon death was everywhere. Fathers abandoned their sick sons. Lawyers refused to come and make out wills for the dying. Friars and nuns were left to care for the sick, and monasteries and convents were soon deserted, as they were stricken, too. Bodies were left in empty houses, and there was no one to give them a Christian burial."

Officials with the Centers for Disease Control and Prevention acknowledged that a series of frightening illnesses linked to insects and pests have been surfacing lately across the country, including mosquito-borne West Nile virus outbreaks in Texas and other states, deadly hantavirus cases linked to Yosemite National Park, and some scattered plague cases.