A microscopic image of Yersinia pestis, the rodent-spread bacteria behind Bubonic Plague. (Photo: Getty Images)
Another case of the plague has occurred in the U.S., officials say — and this time it’s not out west.
A Michigan resident who recently returned home from Colorado has come down with bubonic plague, the Michigan Department of Health and Human Services announced Monday. This is the first known report of a Michigan resident contracting the plague, according to the department.
The unnamed patient is “recovering after receiving appropriate treatment,” officials say, adding that there is no concern of human-to-human transmission in this case. It’s unusual for the plague to be seen as far east as Michigan. However, officials stress that the patient contracted the plague in Colorado, where cases are more common.
This marks the 14th case of the plague in the U.S. this year — double the typical average number of annual cases, per the Centers for Disease Control and Prevention.
Late last month, an elderly person in Utah died of the plague, state officials announced, marking the fourth death from the plague in the U.S. this year.
Officials believe the patient may have contracted the disease from a flea or after having contact with a dead animal, which is how the plague is commonly transferred to humans. The plague naturally occurs in Utah and is typically seen in the prairie dog populations each year, officials said in a press release. The disease is caused by Yersinia pestis bacteria.
Related: Examining the West’s “Plague Line”
That news came less than 10 days after officials in California announced that a Georgia resident who camped at California’s Yosemite National Park fell ill with what is believed to be the plague. That was the second case in August of a person contracting the plague after visiting the park.
The first was a child who went to the hospital with the plague after camping at Yosemite.
There have been two plague-related deaths in Colorado alone this summer. One adult died in early August after contracting the plague from an unknown source. The Pueblo City-County Health Department has not revealed his or her identity but said the person may have developed the disease after coming into contact with fleas on a dead rodent or other animal. The department also noted that a dead prairie dog in the western part of the county tested positive for the disease.
In June, Colorado teenager Taylor Thomas Gaes died just days after coming down with flulike symptoms caused by the septicemic plague, which he was thought to have contracted from a flea bite, the Denver Post reports.
Plague cases reported this year have been contracted in Arizona, California, Colorado, Georgia, New Mexico, Oregon, and Utah. All the cases were believed to have been contracted west of what infectious disease specialists call “the plague line.”
Related: Where Plague Happens in America
The plague line is a geographic marker that delineates areas of the U.S. in which the plague is most likely to occur due to migrations of rodent populations that carry the disease, infectious disease specialist Amesh A. Adalja, MD, an assistant professor at the University of Pittsburgh Medical Center, tells Yahoo Health.
Adalja says the West’s plague cases could be linked to a plague outbreak that happened in San Francisco around 1900, which “seeded the American rodent populations.”
The last urban plague epidemic in the United States occurred in Los Angeles from 1924 through 1925, according to the CDC. The plague spread from urban rats to rural rodents and became entrenched in many areas of the western U.S.
While experts say cases of the plague are rare, Adalja admits that we’re experiencing a higher than normal year — the second highest year on record for plague cases. The highest year was 2006, in which there were 17 cases, according to CDC data.
But Adalja cautions that people shouldn’t panic. “When you deal with numbers this small, any one is going to make a difference,” he says. “It’s a rare disease, and we’re still in what is considered a ‘normal’ range. These cases are occurring in a part of the country that we would expect.”
Adalja says we need more data on the activities of the patients to better determine what’s behind the rise in cases but says it could be tied to the drought that has been happening out west.
The rodent population may be looking for more food sources in campgrounds because of the drought, he says, or fleas may jump from animals that are dying due to the drought onto humans. “It likely has to do with a whole host of factors,” he says.
However, he expects plague cases to dwindle shortly, as the weather turns colder and people spend less time outdoors. Plague cases are typically seasonal, with most occurring between late spring and early fall.
Symptoms can vary depending on the type of plague a person contracts. But a high fever is present in nearly all cases, as well as flulike symptoms. People with pneumonic plague may also develop a bloody cough, and those who contract bubonic plague usually experience painful swollen lymph nodes.
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