Poverty

Unfortunately the lower class makes up for roughly 75% of the people in this world. Meaning a lot of them fall on or under the poverty line, therefore the main cause of death is poverty. Poverty is restricted access to food, proper housing, medical aid, money, education etc 
While there are kingdoms, people and crusaders (much like Vasilki) that help the poor, there are few of them and far more people in need.

Type

Neurological