Health officials on Monday reported New Mexico’s first human case of plague in a 43-year-old Valencia County man.

Plague, a fast-moving bacterial infection that can impact the lungs, blood or bodies’ lymphatic symptoms, is a risk throughout the Western U.S. Infections are classed by the affected parts of the body. The most common infection is bubonic plague in the lymph nodes. Other types include plague in the lungs, called pneumatic, or blood infections, called septicemic plague. Plague spreads by fleas infected with bacteria that circulate in rodent populations such as mice, rats, prairie dogs or rabbits. It is most often transmitted to people and other domestic animals through infected fleas, but also through direct contact with infected animals.

The man, who was hospitalized and later released, received antibiotic treatments for both bubonic and septicemic plagues.

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The source of the plague remains unclear, health officials said, noting the man had camped in Rio Arriba County and may have been exposed there.

“People who live or spend time near wild rodent populations in rural areas of the state should be aware of the risk of plague that is present,” New Mexico State Public Health Veterinarian Erin Phipps told Source NM.

Since 1970, approximately half of the U.S. plague cases have occurred within New Mexico — 250 infectionsduring that time period — according to data from the New Mexico Department of Health. The most recent infection was a fatal case, killing a Lincoln County man in 2024.

Human plague symptoms include a sudden fever, chills, headache or weakness, often accompanied by a painful swelling in the groin, armpit or neck. Plague symptoms in pet cats and dogs include lethargy, loss of appetite or a swelling under the jaw.

Phipps said plague prevention includes avoiding contact with sick or dead rodents or rabbits; clearing up debris to prevent rodent infestations; using insect repellent while outdoors; talking to veterinarians about flea control for pets; and removing pet food and water to prevent wildlife access.

Phipps urged New Mexicans to see a doctor if they experience a sudden or severe fever, saying that while antibiotics are most effective at the beginning of an infection.

“The challenge with plague often is starting that treatment quickly, because plague can progress and become very severe, very rapidly,” Phipps said.