Parts of a wildlife refuge near Denver, Colorado, remain closed after a colony of prairie dogs was infected with plague, a serious bacterial infection that can spread to humans, the U.S. Fish and Wildlife Service announced.

Although certain areas of the Rocky Mountain Arsenal National Wildlife Refuge, which stretches roughly 15,000 acres, is now open to visitors after shutting completely in July, other parts will likely remain closed until early September, officials said.

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The refuge was closed in July “as a precautionary measure to prioritize visitor health and safety,” officials said.

To prevent the spread of the infection, refuge employees have covered prairie dog colonies with insecticide powder to kill plague-infected fleas.

Plague – sometimes called the “black plague,” according to Healthline – is a potentially deadly infection that is caused by a strain of bacteria known as Yersinia pestis.

“This bacterium is found in animals throughout the world and is usually transmitted to humans through fleas,” Healthline notes.

Though rare, plague can equally affect animals and humans.

Symptoms of plague include fever, extreme exhaustion, headache, chills, vomiting, and swollen lymph glands, among other signs.

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The disease is more common in areas with poor sanitation or overcrowding, according to Healthline. Using insect repellent in flea-heavy areas and avoiding contact with rodents or dead rodents are two precautionary steps that can help avoid being infected with the plague.

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Those who live in an area where the plague has been confirmed should not let their pets – dogs included – roam freely.

"Refuge staff will continue to monitor prairie dog colonies and implement plague management efforts," wildlife officials added.