The transportation network like rail and roads were almost completely absent in African Continent before the process of colonization.
The African rivers were the only reliable and easy means of navigation through which the exploration of interior parts of the continent could be gained but these rivers were difficult to navigate without mechanized boats.
Many health challenges were encountered by the outside during the exploration in the interiors of Africa. Malaria and Yellow fever were the most dreaded diseases.
The security challenges were also quite serious in African Continent.
Till the middle of 19th century AD, waterproof bullets were not available and because of that it was difficult to use weapons in rain-infested parts of Africa.
Also in densely forested areas, the tribal population was also a serious security threat.