In José Saramago's dystopian novel Blindness, what epidemic suddenly affects the population?

In José Saramago's dystopian novel Blindness, the population is struck by an epidemic of sudden white blindness.

The first victim loses his sight while waiting at a traffic light, and the condition rapidly spreads through the population. Unlike ordinary blindness, the victims describe seeing a milky or luminous whiteness rather than darkness, which gives the epidemic its distinctive name in the story.

The authorities respond by placing infected people and suspected contacts in quarantine. The breakdown of institutions exposes both cruelty and solidarity, while an unnamed woman who can still see becomes a crucial witness to the collapse around her.

Saramago leaves the medical cause unexplained. The novel is therefore less a conventional outbreak mystery than an allegorical examination of social behavior, moral responsibility, power, and the fragility of civilization. It should not be confused with a story about a literal plague of darkness.