A 10-year-old girl contracted the plague and died in Colorado earlier this month. Her death was the first in the state to be attributed to the plague in six years.
Although the plague is often thought of as a disease of the past, scattered cases still show up in rural areas of the western US.
The last time someone died of plague in the US was last summer in New Mexico, Insider previously reported. The most recent plague deaths the US Centers for Disease Control and Prevention have on file occurred in 2015, when four people died and 16 tested positive for plague.
The recent death occurred in La Plata County, where lab tests have confirmed the presence of plague in fleas. Humans who get it are usually exposed via flea bites, although it's not clear how the girl was infected.
The Colorado Department of Public Health and Environment also identified plague in Huerfano, Adams, San Miguel, El Paso, and Boulder counties, according to CBS4 Denver.
"In Colorado, we expect to have fleas test positive for plague during the summer months. Awareness and precautions can help prevent the disease in people," Jennifer House, deputy state epidemiologist, said in a statement.
According to Denver Public Health, the plague can be treated relatively easily with antibiotics if it's caught within 24 hours of symptom onset. After that point, the infection can begin to cause serious illness or death.
House urged residents to look out for flu-like symptoms and seek medical help if they believe they might have the plague.
