By intentionally spreading illnesses and selling imported medicine
Explanation:
Introduction of slave trade led Africans follow a new pattern of livelihood by staying near the forests in order to secure them. These jungles were the breeding grounds for bugs and flies which were venomous this led to many lakhs of African die out of infections and they died sleeping. More contact with European settlers made them infected with small pox.
Europeans also deliberately induced virus which caused cholera, yellow fever and meningitis. This they had done in order to make the Africans subdue and surrender to their commands. If they accepted for slave trading, they were given with vaccinations. Thus Europeans were successful in achieving huge profits in making slave trade.
