Final answer:
The scanning tunneling microscope would not be useful for observing the surface features of virus particles, while the other microscopes listed would be helpful.
Step-by-step explanation:
The virologist would NOT find the scanning tunneling microscope useful for observing the surface features of virus particles. The scanning tunneling microscope is mainly used for imaging and manipulating individual atoms and molecules on a solid surface, and it is not suitable for observing biological structures like virus particles. On the other hand, the other options, such as the scanning electron microscope, differential interference contrast microscope, atomic force microscope, and transmission electron microscope, would be useful for observing the surface features of virus particles.