IF you are placed in solitary, and then go about interacting with others – there is a higher likelihood of sickness. This is because your natural immunity drops the longer you are out of the culture. Similarly, hiding away from society to keep from getting the corona virus, makes it more likely when you re-emerge, that you could get sick from the corona virus or some other things.
Often attributed to psychological stress, the drop in immunity is actually the result of gene switching, a sort of adaptation to the environment. This can lead to viruses already in your body activating also. So say you had the corona virus but your immunity prevented its activation, in isolation it could become active.
The longer you are in isolation, the more unattuned your body comes to the ambient environment. As a result it is more likely you will catch something upon emergence.
Isolation results in a drop of natural immunity to pathogens in your environment, and also increased inflammation. As a consequence, a lockdown only makes sense if your body cannot generate effective immunity to a pathogen. That might be because of your genes, your state of health, or because of the pathogen.