A U.S. Squirrel Has the Plague: Are We All Going to Die?

Yes, but probably not of bubonic plague. The very same apocalyptic Black Death does still linger in the U.S., though. It's worth knowing something about.

Setting rat traps, Hugh Stenson uses raisin bread dipped in bacon fat as bait at the site of an abandoned fish cannery in 1963. Stenson was head of the rodent control unit at the U.S. Public Health field station in San Francisco, which guarded against bubonic plague. The unit caught as many as 10,000 rats per year. (Robert W. Klein/AP)

We learned last week that campgrounds outside of Los Angeles were closed after a squirrel tested positive for plague. That sounds strange and scary. Does it mean we're all going to die? Well we are, eventually, but not of plague.

"The plague" has a bad name mainly because of the time in the fourteenth century when it killed a third of the human population. Later epidemics in the nineteenth century in China and India also killed millions. The U.S., though, has been relatively spared. In 1925, Los Angeles weathered a much smaller epidemic of bubonic plague — the bacterium having been introduced to the U.S. in 1900 via rat-infested ships from Asia — but that was the last urban epidemic.

Unlike other seemingly anachronistic infections, like smallpox — of which there hasn't been an organic case since 1977 — a handful of Americans still get diagnosed with the plague every year, mostly in the rural Southwest. We saw as many as 40 cases in 1983.

This is the very same plague that killed Europe so long ago, and it can be fatal, but it has a good prognosis when recognized and treated with antibiotics.

Counties Reporting Cases of Bubonic Plague, 1970-2012

CDC

Humans are incidental hosts of the bacteria that causes the plague (Yersinia pestis) which mainly affects other animals. It can and does regularly wipe out prairie dog colonies in a matter of days, maybe just to remind us how powerful it is. (Though it's often actually helpful to control prairie dog overpopulation.)

Bubonic plague is usually spread by getting bitten by an infected flea. When you get a bite, within a couple days you get a fever, headache, weakness, and one or more swollen, painful lymph nodes. The giant infected lymph node — the location of which also tells you where your flea bite was — is called a bubo. Which sounds cute but is not.

As the bacteria spread through the lymphatic system and sometimes the blood, our limbs can turn necrotic and black, and it can be deadly (Black Death).

Seven-year-old Sierra Jane Downing smiles during a news conference about her recovery from bubonic plague at the Rocky Mountain Hospital for Children in Denver, September 2012. It is believed Downing caught the bubonic plague from burying a dead squirrel. (Jack Dempsey/AP)

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There are still parts of the world where bubonic plague mortality rates are high. The World Health Organization records between 1,000 and 2,000 cases every year, though they're likely missing many that go unreported.

Cases of Bubonic Plague, 2000-2009

Dots placed in center of affected countries (CDC, Data via World Health Organization)

The California campgrounds where the offending squirrel resided will be closed for "at least seven days." After that, happy camping! General preventive guidelines still apply, though, as always. (CDC: "Do not pick up or touch dead animals.")