Dysentery is a tier 4 symptom. By breaking down the host's digestive tract, the plague can spread through infected sewage. This also badly dehydrates the host through watery diarrhoea. It renders the villi in the small intestine ineffective, starving the carrier to its death.
The Neurax Worm has two different ways to win. In addition to just simply killing everyone and wiping out humanity (which will unlock the Worm Food achievement) the Neurax Worm can also enslave humanity and force them to worship it through the Transcendence symptom.
You might as well see something worth your time if you dedicated a segment of your life to reading this trash.