Answer :
The phenomenon for which small mutations gradually change the surface antigens of a virus so that antibodies to the original virus become fewer effective is known as antigenic drift.
What is the antigenic drift phenomenon?
The antigenic drift phenomenon is a process in which a virus loss its infection potential due to mutations that hamper the ability of binding of this infectious agent.
Therefore, with this data, we can see that the antigenic drift phenomenon is able to drastically reduce the ability of a virus to infect suitable host such as a human host in the case of some retroviruses.
Learn more about the antigenic drift phenomenon here:
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