Characters in LOST were deathly afraid of The Sickness.
The Sickness manifested as a severe mental change on the part of the afflicted. In 1988, shipwreck survivor Robert tried to kill Danielle, his financee. In fact, except for Danielle, her entire party was taken over by the Sickness, which we thought was caused by the Smoke Monster attacking them at the Temple. Danielle began exhibiting what appeared to be similar paranoid delusions, though she claimed to be the only crew member to escape the sickness. Danielle personally killed all other members of her expedition and other characters wrote her off as insane. Sayid, after his infection, killed even more readily than usual, and he said he could no longer feel emotions. The Others were paranoid about the infection. The medical labs were obsessed with reproduction and Claire' baby. They injected her with an alleged vaccine, which did not work. Claire post-infection became a mentally unstable, paranoid murderer and cradled a boar's skull to replace her baby.
What is believed the infection was in reality a demonic mind possession by MIB (Smoke Monster). It was part of his plan/game to get back at Jacob, who kept his "imprisoned" on the Island. If MIB could develop an army of infected followers, he could take down Jacob to get his freedom. In the last season, MIB was succeeding in the role as fake Locke when he massacred the temple occupants. Those who survived but not directly infected, were controlled by fear. Once there free will was compromised, they could be manipulated against Jacob.
It is a natural human instinct to fear the unknown. Death is the greatest unknown. Something you cannot see in the darkness, is a great unknown. A virus so small it is invisible can enter one's body to reek havoc. In today's panic world, daily updates of confirmed cases and fatalities has the world on edge.
People are told to stay at home. Shelter in place. They have panic purchased supplies including a vast run on toilet paper. It gets to a point of irrational behavior.
Just as in LOST's story line, it plays out in a similar fashion in real life.