[toufka]

The mutations themselves are random. Generally it's reasonable to think of mutations as movement across an energetic landscape. And like in physics, nearly anything is possible if you give it enough time/energy. However, if constrained, the shortest path is usually the most likely.

Back to your question - is there an indicator to predict whether a virus will evolve towards or away from its effectiveness. Ideally, you'd put such constraints on the virus in other ways (in addition to the above concept/treatment), that it wouldn't have the energy/time to get to that much more complicated state of binding more proteins. Every additional mechanism a virus uses is a significant penalty against something as compact and efficient as a virus. But in the end there is likely no way to make any treatment perfect and unovercomable. Best we can do is defend.