As noted in prior posts, Aspen trees in the West have been dying. There appears to be no single cause. However, drought in the 1990's and early 2000's probably made the trees more susceptible to cankers, fungi, and other maladies. The result is that some sites have lost as much as 2/3 or more of their Aspen trees.
In areas that have been particularly hard hit by the die-off of trees researchers have found that there is an explosion of deer mice. Unfortunately, deer mice are a major vector for the sin nombre virus aka hantavirus. Infected mice manifest few outward signs, but humans inhaling the virus from mouse urine or saliva become infected. The disease then moves forward to what is known as the hantavirus pulmonary syndrome. Unknown to medicine until 1993, hantavirus pulmonary syndrome starts with muscle aches, chills, fever, and stomach upset. Later, fluid fills the lungs; more than a third of victims have died. In 2010, the CDC logged 560 cases in 32 states stretching from California to Maine, but mostly in the West.
This is another example of repercussions that flow from rapid changes to and from fragmentation of the environment. Such changes can have deadly adverse consequences for humans.
The study results were report at the January 4, 2011 meeting of the Society for Integrative and Comparative Biology. Unfortunately, the results have not been published. An earlier paper about a like topic by the same researchers can be found at http://www.ingentaconnect.com/content/klu/442/2008/00000155/00000003/00000922