Inclusion Criteria:

You may be eligible for this study if you:

• Are 12 years of age or older.
• Are not pregnant.
• Agree to practice sexual abstinence or use accepted barrier methods of birth control/contraception.
• Are not breast-feeding.
• Have a positive blood test for hantavirus.
• Have symptoms suggestive of hantavirus illness.

Exclusion Criteria:

You will not be eligible for this study if you:

• Have severe low blood count (anemia).
• Have a diagnosis of other respiratory viruses (influenza, RSV, etc.).
• Have group A Streptococcus with symptoms of streptococcal pharyngitis, a positive culture from a normally sterile site, or symptoms of bacterial pneumonia.
• Are HIV positive.
• Have cancer.
• Have had any period of irregular heartbeat.
• Have had chemotherapy or other drugs that suppress the immune system within 30 days.
• Have taken by mouth or injection any antiviral drug (other than acyclovir, famciclovir, amantadine or rimantadine.)
• Have taken by mouth or injection corticosteroids equivalent to approximately 0.5 mg/kg prednisone.
• Have taken any experimental drug within 30 days prior to enrollment.