What factor prevented European prior 1860 from exploring the African interior?

Prior to 1860, European exploration of the African interior was largely hindered by a combination of geographic barriers, such as dense jungles, vast deserts, and challenging river systems, which made travel difficult. Additionally, the prevalence of tropical diseases like malaria and yellow fever posed significant health risks to explorers. Furthermore, limited knowledge and understanding of the continent's cultures and political landscapes contributed to hesitance in venturing beyond coastal regions. These factors combined to create a formidable obstacle to deeper exploration.