Symptoms of these conditions had been known for quite a long time, before any possible identification of the pathogens involved which cannot be seen with an optical microscope. Still today specific antiviral medications remain to be developed. The Colonial Medical Corps has been able to provide its contribution to the prevention of these viral diseases with the development and the distribution of vaccines such as the one for the prevention of yellow fever or through setting up facilities for the manufacturing of rabies and smallpox vaccines, and also with the use of other vaccines shortly after their development such as the poliomyelitis and measles vaccines.