There is no set date for beginning and end of RSV. It varies by region and has varied year after year. Typically it is from November and can end anywhere around April. RSV is scary, my son got it at 3 months old ad was hospitalized from Thursday to Sunday morning. Sadly I do not believe there is anyway to completely prevent RSV, just make sure you keep others away from your new ones face and hands and make sure they wash their hands and face.
I have been told the higher risk ends around the end of April and into May. The Dr's have been telling me that this season it seems everything came late including the flu. Sadly our LO's are never fully in the clear because RSV outbreaks can strike all year round. Check out MD on that website and you will see a spike in like the middle of June/July.