A boy in Idaho is recovering after contracting plague – the first human case in the state in more than two decades, health officials say.

Christine Myron, a spokeswoman for the Central District Health Department, said on Wednesday that the child, who has not been publicly identified, is back home in Elmore County, Idaho, and "doing well" after being treated with antibiotics in the hospital.

The child became ill late last month and, earlier this week, health authorities received laboratory confirmation that he had bubonic plague, Ms Myron said.

Bubonic plague is the most common form and known for causing swollen lymph nodes or "buboes," according to the World Health Organisation. Pneumonic plague, which is based in the lungs, "is the most virulent form of plague" and "can be fatal" when not diagnosed and treated early on, according to the WHO.

It is still unclear whether the child in Elmore County was exposed to the disease in Idaho or during a recent trip to Oregon, according to the Central District Health Department. It said that in 2015 and 2016, the disease was discovered in ground squirrels in Elmore County as well as nearby Ada County. No cases have been reported this year.

Ms Myron said human plague cases in the state are rare, with the most recent cases reported in 1991 and 1992.

Symptoms of bubonic and pneumonic plague are similar and include headache, fever and chills, and extreme weakness, according to the Centres for Disease Control and Prevention.

The CDC states that those with bubonic plague may also experience swollen lymph nodes and that those with pneumonic plague may experience pneumonia along with chest pain, coughing and trouble breathing.

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Sarah Correll, an epidemiologist with the Central District Health Department, said in a statement that plague can be spread to humans when they are bitten by infected fleas.

"People can decrease their risk by treating their pets for fleas and avoiding contact with wildlife," Ms Correll said. "Wear insect repellent, long pants and socks when visiting plague-affected areas."

To help prevent plague, the CDC recommends the following:

--Reduce rodent habitat around your home, workplace and recreational areas.

--Wear gloves if you are handling or skinning potentially infected animals to prevent contact between your skin and the plague bacteria.

--Use repellent if you think you could be exposed to rodent fleas during activities such as camping, hiking or working outdoors.

--Keep fleas off your pets by applying flea-control products.

--Do not allow dogs or cats that roam free in endemic areas to sleep on your bed.