Complex sentence: It was clear to the organizers of the American effort that previous efforts at disease control had been largely ineffective, as the causes of the two main diseases were unknown, but in 1897 it was proved by Britain's Ronald Ross in India that malaria was treatable.
Split into simpler sentences: It was clear to the organizers of the American effort that the pvious projects. Previous efforts at disease control had been largely ineffective, as the causes of the two main diseases were unknown, but in 1897 it was proved by Britain's Ronald Ross in India that malaria was treatable.