Current recommendations for control of secondary smallpox infections emphasize transmission "by expelled droplets to close contacts (those within 6-7 feet)" (Centers for Disease Control, 2002 Control, , 2003 . Recommendations include vigilant maintenance of standard, droplet, and airborne precautions. However, emphasis on spread via large droplets may reduce the vigilance with which more difficult airborne precautions are maintained. High concentrations of variola in the lung during the incubation and prodromal periods in monkeys after simulated use of variola as a bioweapon (Hahon, 1961 ) may indicate that first generation cases after an attack with a concentrated aerosol may be more infectious than expected based on historical data. Moreover, because airborne precautions are not routine for all hospitalized patients, and because first generation cases will probably not be initially suspected to have smallpox, it is likely that they will not be placed on airborne precautions until well into their infectious period. Therefore, the extent of transmission to a second generation in the contemporary hospital environment may be greater than expected based on historical estimates.