The negligible increase of NpFU as particle size increases can also result from the adverse

effect of saliva components. The adverse effect of saliva on the stability of viral aerosols has

been reported in a previous study (Barlow and Donaldson 1973). They observed that foot-and-

mouth disease viral aerosols were more unstable when generated from bovine salivary fluid than

from cell culture fluid at HRH, and they postulated the presence of an "inactivating factor" in the

saliva as the reason for instability of viral aerosols. In later studies (Fox et al. 1988; Bergey et al.

1994; van der Strate et al. 2001; Hartshorn et al. 2006), an antiviral effect of saliva on HIV-1 and

influenza A virus was observed and some proteins of saliva such as lactoferrine, agglutinin, and

mucins were proven to be the inactivating factors.

 Table 4-10 shows NPFU/, at three RHs. The values at LRH and MRH were similar to

those for MS2 aerosols generated from tryptone solution, indicating a similar adverse effect. At

HRH, the values were lower than those from the tryptone medium. Both inactivation effects

from salivary components and from the air/water interface can be factors. The protective effect

of tryptone at HRH was not observed for artificial saliva, showing again the adverse effect of

saliva components. However, no synergistic effect of these two factors was observed since the

NPFU/V i values were similar to those for MS2 aerosols generated with DI water, which were

adversely influenced only by the air/water interface.

Distribution of MS2 in aerosol particles generated from different spray media

 As presented in Tables 4-3 and 4-5, the distribution of MS2 including both infectious

and total (infectious and non-infectious) viruses along the aerosol size ranging from 30 to

230 nm was investigated. The n values for NRNA and NPFU for aerosols generated from DI water

and from tryptone solution were different, although the difference was less for tryptone solution

than for sterile DI water. On the other hand, MS2 aerosols generated from saliva showed a much