Sudden outbreak of worms reported in South Korea’s water supply
City officials believe that insects may have laid eggs in water treatment facilities as an urgent investigation is ordered
This is happening in many cities at the same time.
My bet is that some environmentalist got them to change the water treatment system. Perhaps chlorine is that poison that Greenpeace says it is (some environmentalists really have gone after chlorine as a water treatment, causing cholera outbreaks as a result) or summat like that.