There are some science fiction tropes that become really obvious when you start looking for them. For one, check out Invasion of the Body Snatchers or Heinlein's Puppet Masters: that's "the Commies are among us", and it's not surprising that it became a significant thing in the 1950s. Although the idea that there are a group of people out there who look and act completely normal but who are actually out to destroy everything that decent people hold dear is a pretty common fear; demonic possession and all.
The Zombie 'Pocalypse is another. Charlie's right, it is the same fear as that of the owners of an antebellum Southern plantation at the mention of a slave uprising. The idea that all of the people you live with every day might suddenly turn into degenerate, savage monsters yearning to snack on your favorite nervous system is pretty scary, though. But it doesn't really have anything to do with infection or disease, and he is wrong to try to tie the two together. The infection isn't the important part.
Oh, and let's wait until the next time something like the current pandemic happens before we pass too much judgement on how people react. Consider the difference between the Northeast blackout of 1965 and the New York City blackout of 1977.