An unusual resurgence of the plague in the United States this year has left three dead and eight others sickened across six states, according to the Centers for Disease Control and Prevention (CDC).
Since April 1, 11 total cases of the plague have been reported in Colorado (4), Arizona (2), New Mexico (2), Oregon (1), Georgia (1) and California (1), according to the CDC’s most recent Morbidity and Mortality Weekly Report. Three people have reportedly died of the illness, including two in Colorado.
The cases in Georgia and California originated from visits to the Yosemite National Park, the CDC reported. A Georgia resident and a young girl from Los Angeles County were both found to have contracted the illness after visiting the park this year.
The 11 cases reported so far this year are the most since 2006, when 17 cases were reported nationwide, according to Fox News. There were an average of seven cases of plague per year between 1970 and 2012.
“It is unclear why the number of cases in 2015 is higher than usual,” the CDC reported.
Dr. Bruno Chomel, a professor at the University of California, Davis School of Veterinary Medicine, told Fox News that California’s record drought may be playing a role in the increase in plague cases. Plague is often transmitted to humans through the bites of infected fleas, and rodents carrying those fleas may be scavenging for food near campgrounds as food options become scarce due to drought, Chomel told the outlet.
Infectious disease specialist Dr. Amesh Adalja told Fox that Chomel’s rodent theory appears to check out.
“These cases are occurring in locations where we know that plague exists in the [rodent] population,” Adalja said.
When left untreated, the mortality rate for plague cases ranges between 66 to 93 percent, according to the CDC. However, antibiotics available today have reduced the mortality rate of the plague to approximately 16 percent.
The CDC urges people engaging in outdoor activities in areas where the plague is known to occur to wear long pants, use insect repellent and avoid contact with sick or dead animals.