The purpose of this study is to evaluate pharmacokinetics, safety, tolerability, antiviral activity, and impact on the clinical course of Respiratory Syncytial Virus (RSV) infection after multiple oral doses of JNJ-53718678 at different doses and/or dosing regimens in infants (greater than [>] 1 month to less than or equal to [<=] 24 months of age) who are hospitalized with RSV infection.