Patient Inclusion Criteria

1. 18-80 years of age. 2. Asymptomatic with close contact within the last 5 days with a person known to have possible SARS (SARS RUI-2 (SARS Report under investigation), RUI-3, RUI-4) or probable SARS or confirmed SARS using the Centers for Disease Control and Prevention (CDC) Supplement B: SARS Surveillance, Appendix B1: Revised Council of State and Territorial Epidemiologists (CSTE) SARS Surveillance Case Definition (Attachment II). 3. Oral temperature < 100.4°F (<38°C) 4. Subjects must be asymptomatic with regard to SARS related clinical symptoms including any signs of a respiratory illness. 5. Serum creatinine ≤ 1.5 x ULN (upper limit of normal); serum bilirubin ≤ 1.5 x ULN. 6. Total white blood cells (WBC) ≥ 3000/mm3, platelet count ≥ 100,000/mm3 and granulocytes ≥ 1500 mm3. 7. Hemoglobin > 10.0 g/dl. 8. ALT (alanine aminotransferase) and AST (aspartate aminotransferase) < 4 times upper normal limit. 9. C-reactive protein serum level in normal range 10. Serum albumin > 2.0 g/dl. 11. Written informed consent. 12. Females must either be of non-child bearing potential, or utilize an effective form of contraception and have a negative pregnancy test prior to randomization.

Patient Exclusion Criteria

1. Pregnant or nursing women, or women not using an effective form of contraception. 2. Less than 18 years of age. 3. Active intravenous (IV) drug users. 4. Receipt of any immunosuppressive agent, chemotherapy, or systemic steroids within 45 days of study entry. 5. Receipt of any immunomodulator such as BCG (bacille Calmette Guerin) vaccine, isoprinosine, or similar experimental agents within 45 days of study entry. 6. Evidence of HIV or other viral infections including chronic hepatitis, or other active gastrointestinal, renal, respiratory, endocrine, hematologic, cardiovascular, neurological, or psychiatric disorder that would limit the subject's ability to complete the study period. 7. Unlikely or unable to comply with the requirements of the protocol. 8. Patients unwilling or unable to give informed consent. 9. Patients on any other concurrent experimental medication. 10. Patients using any form of interferon therapy during the 6 weeks prior to study entry. 11. Hospitalized subjects, or those with an active viral infection other than possible SARS, within 2 weeks of study entry. 12. Transfusion dependent subjects (subjects requiring > 1 unit of packed RBC [red blood cells] per month within the 3 months prior to study entry).