FIG. 4.

IFN treatment blocks transmission of Cal/04/09 virus among guinea pigs. (A) Lack of transmission of Cal/04/09 virus from IFN-treated donor guinea pigs. Four guinea pigs treated intranasally with IFN on days −1 to 5 postinfection were infected with 10⁴ PFU of Cal/04/09 virus (open squares with dashed lines). Eight naïve guinea pigs, treated with either IFN (open triangles with solid lines) or PBS (filled triangles with solid lines), were exposed by being placed in the same cage with one infected animal. Transmission was not observed to either IFN- or PBS-treated guinea pigs. (B) Lack of transmission of Cal/04/09 virus to IFN-treated recipient guinea pigs. Four guinea pigs treated intranasally with PBS alone on days −1 to 5 postinfection were inoculated with 10⁴ PFU of Cal/04/09 virus (filled squares with dashed lines). Eight naïve guinea pigs, treated with either IFN (open triangles with solid lines) or PBS (filled triangles with solid lines), were exposed by being placed in the same cage with one infected animal. Transmission was observed to all four PBS-treated animals but to none of the IFN-treated guinea pigs.