A person is being treated for plague at a Denver hospital after contracting the disease during a recreational trip to southwest Colorado, according to Archuleta County health investigators.

This is the first confirmed case in human plague in Colorado since 2006. The last case of plague diagnosed in a human in Archuleta County was in 1998, The Denver Post reported.

The person is believed to have contracted the disease while “recreating with family” northwest of Pagosa Springs in the Cimarrona Campground near Williams Creek Reservoir in the San Juan National Forest.

San Juan Basin Health is coordinating with Colorado Department of Public Health and Environment and the National Forest Service to post warning signs in the campground and vicinity. It is common for plague to spread through rodent populations in a localized area – often resulting in mass “die-offs”, San Juan Basin Health department officials said in a news release. Rodent die-offs regularly occur in the southwestern U.S.

According to the Centers for Disease Control and Prevention, there are typically an average of seven human plague cases reported each year in the U.S. Most occur in rural areas and predominantly in northern New Mexico and Arizona, southern Colorado, California, southern Oregon and far northwest Nevada.

Six animals — including squirrels, household cats and prairie dogs — tested positive for plague in Colorado in 2011. Two animals have tested positive for plague so far this year.