Review the map. An untitled map of Europe showing the spread of the bubonic plague by marine routes. In 1347 the bubonic plague followed marine routes, spreading to nearly all countries along the coast by 1348. The plague spread further inland between 1348 and 1351. Areas further inland were least affected by the plague. Based on the map, why were some areas left relatively unaffected by the plague? They had a strong church presence. They were far from places like Asia. They had limited contact with trade routes. They had less diverse religious populations.