The purpose of this trial is to conduct a randomized dose-ranging study to evaluate the safety and activity of orally administered low dose interferon alfa-n3 as an antiviral and immunomodulator in asymptomatic subjects with recent exposure to a person with severe acute respiratory syndrome (SARS) or possible SARS. The primary objective of this pilot study is to determine an Alferon LDO dose level that increases or upregulates genes known to be mediators of interferon response. Secondary endpoints include the development of SARS symptomatology, rate of hospitalization, and mortality rate. In the event that no subjects with recent exposure to a person with SARS or possible SARS are available, this study will be conducted with 10 normal volunteers.