Respiratory syncytial virus(RSV)is a leading cause of lower respiratory tract disease.The major high risk population for RSV infection are<6month infants and elders with age older than 65 years.At present,BALB/c mice were wildly used as animal model for RSV infection,however there has no report about the comparison of different week-ages BALB/c mice after RSV infection.A different week-ages BALB/c mice model was described in this study to compare their susceptibility after RSV infection.Young(10weeks),middl...