Three people have been infected so far. Why is this disease still found in parts of the western United States?

Health officials in New Mexico are warning pet owners to be careful.

The advisory comes after three people were diagnosed with the plague this year.

“Pets that are allowed to roam and hunt can bring infected fleas from dead rodents back into the home, putting you and your children at risk,” Dr. Paul Ettestad, public health veterinarian for the Department of Health, said in a statement this week. “Keeping your pets at home or on a leash and using an appropriate flea control product is important to protect you and your family.”

The most recent cases of infection were two women, ages 52 and 62 years.

It was confirmed this week that they were infected with the bacterial disease, according to the New Mexico Department of Health.

All three people diagnosed with the disease were hospitalized, but none have died.

Officials from the health department are now investigating the homes of those infected to ensure there isn’t a risk to families or neighbors.

Is the bubonic plague making a comeback?

While the bubonic plague may seem to be a disease of the past, the bacterial disease remains endemic to rodents and prairie dogs in the southwest region of the United States.

The disease first came to the United States via rat-infested ships, according to the Centers for Disease Control and Prevention (CDC). Today, most cases occur in the Southwest, California, southern Oregon, and far western Nevada.

Dr. William Schaffner, an infectious disease expert at the Vanderbilt University School of Medicine, explained people who venture outdoors near rodents or prairie dogs may be at increased risk.

“If you get into their environment … the fleas sense your warmth and they think you’re a prairie dog and bite you,” said Schaffner.

Additionally, pet owners can be at particular risk because their dogs may bring in the infected fleas.

“They can go out and pick up the fleas and bring them home, and as you snuggle with your pet they go from your pet to you,” Schaffner explained.

Few campers concerned about plague new Yosemite

If a person is infected with the plague, the classic early symptom is swollen lymph nodes.

“The plague bacteria go to [the] lymph nodes and set up shop,” said Schaffner. “Most people have their infection localized like that, but if the plague bacteria get into the bloodstream it can make you very, very sick.”

Other symptoms include fever, chills, and headache.

In pets the disease can manifest in symptoms such as fever, lethargy, and loss of appetite.

Schaffner pointed out that visitors to the areas where most cases occur should be especially careful since their doctors may not know the early symptoms of plague infection.

“The diagnosis may be delayed, and then the patient is at greater risk,” he said.

Those sickened with the disease can usually be treated with antibiotics to fight the bacterial infection.

The New Mexico Department of Health reported there have been at least eight cases of plague in the state from 2015 to 2016, with one person dying after contracting the infection.

The department advises pet owners to talk to their vets about using flea control products, cleaning up areas near their houses where rodents may live, and immediately getting sick pets checked out by their vets.

Additionally, anyone with an unexplained illness and high fever should see their doctor.

Mosquitoes: The most dangerous animal on earth?