I wonder if you might be confusing ease of transmission with virulence.
Both rhinoviruses and polio viruses are very contagious viruses already.
The problem (?) with both is that neither virus is particularly virulent.
Rhinoviruses are highly contagious, but seldom if ever cause more than mild
colds. While most people think of poliovirus as a very dangerous virus, 95%
of those individuals who contract polio never experience anything other than
mild flu-like symptoms or non-paralytic disease. Paralysis is a relatively
uncommon outcome. In fact, the recognition (in the early 1950's) of
sub-clinical polio as the most common outcome of infection was a major
breakthrough in containing polio spread before the widespread availability
of the Salk vaccine.
For a credible fiction novel, pick another virus.