Hantavirus pulmonary syndrome (HPS) has been recognized as a disease only recently in North America.  So far, it's also fairly uncommon and the chances of becoming infected are low.  However, HPS is potentially deadly and immediate intensive care is essential once symptoms appear.

 Deer Mouse
Deer Mouse  (Peromiscus maniculatus)

Hantaviruses that cause HPS are carried by wild rodents, especially the deer mouse, but do not infect pets or livestock. You can become infected by inhalation of their droppings, urine, or saliva. You can also be infected by direct contact (bites, wounds, or contact through the mouth and eyes). You cannot catch HPS from another person. The first signs of sickness (especially fever and muscle aches) appear 1 to 5 weeks following exposure, followed by shortness of breath and coughing. Once the respiratory phase begins, the disease progresses rapidly, necessitating hospitalization and often ventilation within 24 hours. HPS can also cause severe damage to the lungs and kidneys.

You can prevent inhalation of hantavirus by ensuring adequate ventilation before cleaning rodent infested areas. Allow the room to air out for at least 30 minutes before entering. Spray dust and droppings with 10% bleach, and let soak for at least 5 minutes. Do not sweep or vacuum dried rodent droppings! 

Center for Disease Control and Prevention: Hantavirus 
Colorado Department of Public Health and Environment: Hantavirus 
Center for Food Security and Public Health: Hantavirus