The slave trade grew rapidly during the exploration and exploitation of the Americas due to the demand for cheap labor.
The age of exploration resulted in European countries establishing permanent settlements in different parts of the New World. When establishing these settlements, the explorers encountered new goods and products that would become extremely valuable in European society. In order to maximize their profits on these goods, the colonizers needed a lot of labor. This resulted in several deals made between European leaders and African leaders who were willing to sell their own people into slavery.
The system of slavery would allow for cheap labor and a huge increase in profits for several European countries.
Overcrowding was most directly contributed to the spread of disease in city tenements in the early 1900.
Back then , the city was shocked by smallpox epidemic. Since smallpox is easily transmitted by contact, overcrowded areas are the perfect breeding spot for smallpox ( they still has not developed small pox vaccine back then)
The Habsburg Empire was on the verge of collapse, because these wars caused monumental state debt and financial crisis. The Habsburgs were forced to reconcile with Hungary, to save their empire and dynasty.