Bubonic plague
A close look at the bacteria Yersinia pestis which causes the plague.Wikipedia

A US resident who recently returned from Colorado to Michigan has been confirmed to have contracted the life-threatening bubonic plague. The man was infected while in Colorado and is now recovering, the state's health officials have said.

The rare disease has so far claimed three lives in the US since April, the US Center for Disease Control and Prevention said. However, in the case of the Marquette County resident in Michigan, the deadly disease did not take the pneumonic form, which is fatal.

Pneumonic plague can be passed on to humans, infecting the lungs and causing pneumonia that can lead to respiratory failure and shock. "It's the same organism but, in this case, the infection resides in a lymph node," Dr Terry Frankovich of the Marquette County Health Department was quoted as saying.

"Theoretically, the illness can move to bloodstream or to a lung infection, but this [Michigan] individual had localised infection, so there's no concern about transmission," he added. In the Michigan case, "truly there is no risk to anyone", confirmed the spokeswoman for the Michigan Department of Health and Human Services.

"This is not something that occurs (in) Michigan. ... This is a person who contracted this while they were away, and the individual is making a recovery and is not a public health (threat)," said Jennifer Smith.

This was the 14th case of human plague reported this year, which is more than four times the average of cases registered annually in the country. Previously, an elderly Utah resident died from of the flea-borne illness and in August and two people succumbed in Colorado.