Keep catching RSV

Patient: I’m 62. I’ve gotten respiratory synctitial virus 7 times in the past 5 years, and each time the cough and fatigue have lasted for many weeks – up to 6. Before this, I think I had it once as an adult, in 1978. I used to get a common cold about every 1-2 years; I have not had one in more than 6 years. I’m a little anemic but have no major health problems, and I’m not under stress. I get plenty of sleep. Why would I suddenly develop a susceptibility to this particular virus?