Germs found new life and meanings in the tropics. They added new depth to the phenomenon of putrefaction previously associated with hot climates. Following the emergence of the idea of germs as causal organisms of diseases, European physicians and scientists no longer perceived the tropics as merely hot and miasmatic places, they also, it appeared, saw them as infested with germs. The identification of specific viruses and bacteria for diseases provided both optimism about the European colonization of and habitation in the tropics and, simultaneously and paradoxically, raised new apprehensions about germs in the tropics. While bacteriology provided the possibility that with vaccines colonial diseases could now be rescued from the fatalism of tropical climatology, it also generated new anxieties in colonial medicine. Physicians worried about whether germs behaved differently in hot climates; if tropical fecundity was ideal for the spread of germs; whether the native bodies and habits were peculiarly predisposed to harbor germs; whether vaccines could be produced and preserved in the tropics; and, finally, if bacteriology had to play an even more revolutionary role in the tropical colonies.

Bacteriology emerged in India within the morality and paternalism of nineteenth-century public health and sanitarianism. In India as in Britain, bacteriology in the nineteenth century coexisted with heavy measures of sanitary doctrines. The zymotic theory of the 1870s united the new germ theory with earlier ideas of putrefaction, absorbing the same moral values associated with filth and decomposition.