Objective]The purpose of this study is to test the therapeutic effect of ATO on pneumonia caused by RSV [Methods]TCID 50 of 100 times was applied to infect cotton rats and mice Abdominal injection of ATO (0 5%) started on the same day when the cotton rats and mice were infected Optical and ultramicroscopical pathological changes were studied on the 5th and 10th day of the injection treatment Hep-2 cell strain in vitro was also infected by RSV and ATO of 0 5% was then applied to inhibit RSV;...