Yersinia pestis is tiny—only a fraction of a nanometer wide. But it packs an infectious punch, infecting insects, people and animals with plague that has the potential to fuel widespread pandemics. Though you may think the days of plague are long gone, they're not. As The New York Times’ Liam Stack reports, three people in New Mexico have recently come down with plague.
That’s right: Y. pestis is at it again. Though all three patients have been released from hospitals, it’s a reminder that plague isn’t exactly a thing of the past.
Plague is commonly associated with the bubonic variety that wiped out an estimated 25 million people during the Black Death pandemic in the 1340s and that swept through other populations during the Medieval Era. But bubonic plague is only one of human plague’s permutations—none of which have been eradicated. Each type has slightly different symptoms. Bubonic plague concentrates in the lymph nodes. Septicemic plague includes bleeding beneath the skin. And pneumonic plague causes respiratory problems.
All three varieties begin with fever and weakness, according to the Centers for Disease Control and Prevention. And all three occur because of Yersinia pestis—a species of bacteria carried by fleas that live on rodents like ground squirrels, rats, mice and prairie dogs. Infected fleas can bite humans, but that’s not the only way to get plague. Infected cats can spread it as well, as can breathing in droplets of bacteria expelled from a person or animal with plague. It is not clear which of the three types of plague were present in the latest three cases.
Because plague is spread by rodents, it’s most common these days in places where the environment supports diverse rodent life. As Stack notes, New Mexico has lots of vegetation like juniper bushes that house rodents, and if plague wipes out one species of rodent there are other ones nearby for the fleas to infect. As a result, plague cases are more common in New Mexico and other Western states. However, only a handful of cases are reported each year.
The last major urban outbreak of plague in the United States happened nearly a century ago in Los Angeles. In 1924, a two-week-long outbreak of pneumonic plague swept through L.A., killing 30 people. However, according to the CDC, the vast majority of reported plague cases now occur in sub-Saharan Africa and Madagascar.
So far, this latest incidence of plague has been small. According to the New Mexico Department of Health, the three reported cases are the only ones this year, and nobody has died from reported plague in 2017. With all three cases under control and only a handful of cases in the United States each year, there’s little reason to fear a widespread outbreak anytime soon.
However, animal plague is another story. Eighteen total cases of animal plague were found in New Mexico this year, including 11 dogs and five cats. When pets are allowed to roam and hunt outside, the Department of Health tells The Albuquerque Journal, they can bring infected fleas home with them, potentially endangering their human owners. A Colorado dog ended up being the catalyst for a 2014 outbreak.
All the more reason to keep your pets indoors—and to respect the power of these tiny bacteria.