Spring rains in the Front Range, after years of drought, are leading to thriving populations of mice and other rodents – carrying the rare, sometimes deadly diseases of plague, tularemia and hantavirus.
“It certainly has been a good year so far for the rodent diseases,” said state epidemiologist John Pape.
A man in Weld County is recovering from hantavirus pulmonary syndrome, officials said Wednesday.
An Alamosa County woman died of the same respiratory disease – spread by infected mice – earlier this month.
Plague killed a capuchin monkey at the Denver Zoo last week, after 20 cases were discovered in tree squirrels in the City Park area.
The bacterial disease kills about 18 people annually in the United States.
And at least two cats in southwestern Colorado have tested positive for tularemia this spring.
When the tularemia bacteria hits humans, it is known as “rabbit fever.” About 200 people come down with the fever each year.
“In wet years, we have lots of vegetation and explosive population booms in rodents,” Pape said. “The more dense they are, the better they transmit disease.”
Plague is caused by Yersinia pestis – a form of the bacteria that killed an estimated 25 million people in Europe during the Middle Ages.
It is rare today, but about one in seven people infected dies because the disease is not caught early enough.
Humans usually get plague from infected fleas, which pick it up from squirrels, prairie dogs and other rodents, Pape said.
Plague is always simmering in Colorado’s rodent populations, Pape said, but the disease boils up into an outbreak every five to 10 years, sometimes killing off whole colonies of prairie dogs.
It’s usually during those years that the human cases occur, he said.
In Weld County, a 30-year-old man turned up with another rodent-related disease last week – hantavirus.
The source of the infection has not been determined, said county spokeswoman Gaye Morrison. The man’s name is not being released.
It is usually caught when a person inhales dust contaminated with mouse urine or feces, or through direct contact with mice.
Early last spring, health experts discovered plague at several Front Range locations and feared the disease might take off, Pape said.
“Then it was hot for six weeks and that absolutely shut it off,” Pape said. “During long, hot, dry periods, fleas literally dry up and die.”
Southwestern Colorado stayed relatively cool last spring and all four of Colorado’s human plague cases showed up in the region, said Joe Fowler, a registered nurse and epidemiologist for the San Juan Basin Health Department.
Jessica Hamby, 13, who lives outside Durango, said she spent a miserable four days in Mercy Hospital with plague last summer, feverish and vomiting.
This year, Fowler said, two cats in the southwest suspected to have plague turned up positive for tularemia.
In people, tularemia bacteria can trigger a wide variety of symptoms, from skin ulcers to diarrhea to fever, depending on whether it’s inhaled, ingested or caught from an infected tick or deerfly.
“We do have lots of growth, so humans are encroaching on areas where rodents carrying plague live,” Fowler said.
Staff writer Katy Human can be reached at 303-954-1910 or khuman@denverpost.com.
