Four people in Colorado have now been diagnosed with pneumonic plague.

The Colorado Department of Public Health and Environment said that all four were infected from the same source: an infected dog.

As Jennifer House, the Colorado Department of Public Health and Environment’s public health veterinarian, said, “We usually don’t see an outbreak like this related to the same source.”

Pneumonic plague is the only form of the disease that can be transmitted person-to-person, and is often transmitted through infectious droplets from coughing.

The eastern Colorado man’s dog died of the rare and serious disease. The man remains hospitalized and authorities have not released his condition.

The three others were reported to have had “mild symptoms” and, having been treated with antibiotics, have recovered. The department noted that all three are no longer contagious.

As Fox News reports, the infected Colorado dog is likely to have contracted the disease from prairie dogs or rabbits, which are the primary hosts for fleas that carry the bacteria.

According to the U.S. Centers for Disease Control and Prevention (CDC), the bacteria that causes the plague occurs naturally in the western United States.

Pneumonic plague is one of three forms of the plague. The CDC notes that “early treatment of pneumonic plague is essential. To reduce the chance of death, antibiotics must be given within 24 hours of first symptoms.”

House noted that over the past decade, Colorado has seen a total of 12 cases of humans infected with the plague; not since 2004 has the state had a confirmed case of pneumonic plague.

Sources: Fox News, Tech Times

Photo Sources: Med City News, Fox News