The French Third Republic in Western Africa also employed biopolitics in their colonial efforts. The "fin-de-siecle" revolution in microbiology and specific developments in public health legislation aided the French. Furthermore, thanks to the germ theory of disease pioneered by Robert Koch and Louis Pasteur, the etiology of some of the most deadly diseases—cholera and typhoid—began to be understood in the 1890s, and the French used this new scientific knowledge in the tropics of West Africa. Illnesses like bubonic plague were isolated, and vectors of malaria and yellow fever were identified for the political purpose of public health. They passed public health laws to introduce up-to-date health standards. The goal was for African subjects to respond in exactly the same way as metropolitan citizens to market incentives and new technologies imposed by a progressive state. Thus, public health was a political concern in the sense that the state hoped citizens would be more productive if they lived longer.