Rise in plague cases in recent years is attributable to an increase in rodent population, say experts. The state health department says four cases have been recorded in Colorado in 2015 so far.

An adult succumbed to the disease Wednesday, confirmed the Pueblo City County Health Department. The toll due to the plague has reached two this year.

Fleas that get infection from rodents spread plague in human beings. A surge in rodent population is the result of conducive conditions being set for them to thrive by a lower number of rodent predators, and a wet spring. The situation is worrisome as odds are high for the transmission of the plague.

“We don't have too many coyotes and foxes so we have more rodents and that's how the transmission takes place so the more rodents we have, the more likelihood that we'll have some of these cases”, said County Health Department spokesperson Katie O'Donnell.

More cases of Tularemia or Rabbit Fever could also result from the lack of natural predators, says O'Donnell.

The Weld County health department recently revealed in a report that an uptick was seen in Tularemia cases.

O'Donnell says one must consult a doctor if feels more than cold, aches and pains. Initial diagnosis makes things easier with antibiotics.

Untreated bubonic plague is very dangerous as enters the blood stream and lead to septicemic plague. No treatment means either form of plague can cause pneumonic plague.