How did diseases affect the construction of the Panama canal?

An estimated 12,000 workers had died during the construction of the Panama Railway and over 22,000 during the French effort to build a canal. Many of these deaths were due to disease, particularly yellow fever and malaria.

Explanation:

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place