than a single naked MS2, which can be either the MS2 aggregates or substances with MS2 generated from the nebulizer suspension (virus stock suspension in the nebulizer contains milk proteins and organic molecules for virus preservation). Therefore, infectivity of MS2 can be shielded by the outer layer of the aggregates or by encasement in substances present in the nebulization medium. MS2 aggregation generated from the nebulizer, which is caused by hydrophobic interactions between neighboring protein capsids, has been observed by previous studies (Hogan et al. 2004; Balazy et al. 2006). S High retention capability of the filter The extracted fractions of both iodine-treated and untreated filters are significantly lower than the other regular filter media due to the expected high retention of particles on filter media resulting from electrostatic interaction between filter media and the charged surface of viral particles, as discussed earlier. It should be stated that this interaction will persist due to the inherent electret property of the resin-treated surface. Extracted values close to the detection limit can make the effect of iodine on the virus infectivity indistinguishable. The control experiments carried out in this study with thiosulfate and BSA require that reported data generated in experiments collecting aerosols in aqueous media or on protein gels to measure the biocidal capacity of the iodine-treated filter be reexamined to consider the possibility of competition by dissolved 12. Significant support for the previously proposed mechanism of charge-induced capture of iodine from bound triiodide is found in the observation of significant inactivation persisting in a BSA medium that was able to protect suspended virions from inactivation by impinging I2 vapor. However, toxicity of iodine dissolved in the collection medium is likely to be a competing mechanism in warm environments, and the relative importance of each must be determined-or at least factored into the design and analysis