California just saw its first plague case in 5 years. Experts explain why you shouldn't panic

Health officials in California revealed Monday that a South Lake Tahoe resident has tested positive for plague.

The patient, who has not been publicly identified, is believed to have been bitten by an infected flea while walking their dog along the Truckee River Corridor or in the Tahoe Keys area, according to a press release from El Dorado County’s Health and Human Services Agency. The patient is “currently under the care of a medical professional and is recovering at home,” the press release says.

“Plague is naturally present in many parts of California, including higher elevation areas of El Dorado County,” Dr. Nancy Williams, El Dorado County Public Health Officer, said in a statement. “It’s important that individuals take precautions for themselves and their pets when outdoors, especially while walking, hiking and/or camping in areas where wild rodents are present. Human cases of plague are extremely rare but can be very serious.”

Several areas of South Lake Tahoe have signs that warn the public about the presence of plague and ways to prevent exposure, the press release says.

Plague is a disease caused by the bacterium Yersinia pestis, according to the Centers for Disease Control and Prevention. The plague can infect people and mammals, the CDC says, although people usually get the plague after being bitten by an infected flea or by handling an infected animal. While you don’t hear a lot about the plague these days, the disease is notorious for causing the black death pandemic in the Middle Ages.

Some people are freaking out over the news on Twitter, but infectious disease experts say there’s no need to panic. Here’s why.

The plague has been in the U.S. since 1900

It seems shocking that the plague would show up in the U.S., but it’s been in the country since it was brought over in 1900 on rat-infested steamships that sailed from infected areas, the CDC says. Back then, epidemics happened in port cities.

The last urban plague epidemic in the U.S. happened in Los Angeles from 1924 through 1925, the CDC says. After that, the plague spread from urban rats to rural rodents and “became entrenched” in many areas of the western U.S., including northern New Mexico, northern Arizona, southern Colorado, California, southern Oregon and far western Nevada, per the CDC.

Human cases of the plague don’t happen often, but they do occur. “We may have a dozen cases or so in the country each year,” Dr. Amesh A. Adalja, senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life.

There are three forms of the plague, but more than 80 percent of the cases in the U.S. have been the bubonic form, the CDC says. On average, the CDC says that the country sees between one and 17 cases annually. There have been minimal plague cases over the past few years, though — in 2016 there were four reported cases, in 2017 there were five and in 2018 there were just two reported cases.

What are the symptoms of the plague?

The symptoms of bubonic plague can include the following, according to the CDC:

  • sudden fever

  • headache

  • chills

  • weakness

  • one or more swollen, tender and painful lymph nodes

While it sounds like the symptoms are similar to those of COVID-19, the swollen lymph node is a distinguishing characteristic, Adalja says. “The swollen lymph node is usually solitary and huge,” he says.

The bacteria can spread throughout the body if it’s not treated, the CDC says.

How worried about this should people be?

“You shouldn’t be worried,” Dr. William Schaffner, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Life. However, Schaffner says, it’s best to steer clear of rodents like prairie dogs, which are known carriers of the plague in certain areas of the country. (The El Dorado County Department of Health and Human Services specifically warns about squirrels, chipmunks “and other wild rodents.”)

If you live in an area where the plague is known to surface, Schaffner says, it’s also important to keep your pets away from these rodents. “Dogs and cats can be infected with the fleas that carry the plague, and then infect you,” he says.

Even if someone happens to contract the plague, it’s “very treatable with antibiotics and patients often do well,” Dr. David Cennimo, an assistant professor of infectious disease at Rutgers New Jersey Medical School, tells Yahoo Life. But, he adds, proper diagnosis is important. “The biggest worry would be missing the diagnosis, so it is important to have a good exposure history to know that we should be worried about the potential of infection,” he says.

Still, Schaffner stresses that people shouldn’t worry about this spreading. “This is a very unusual infection,” he says. “There is not going to be an outbreak.”

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