[Representing and intervening in public health: viruses, mosquitoes and Rockefeller Foundation experts in Brazil]

The attempts by experts from the of the Rockefeller Foundation (RF) to eliminate yellow fever in Brazil were hampered by the pathology's low visibility. Most cases of yellow fever were atypical and easily confused with other fevers. In the 1920s, the RF experts who tried to assess the presence of yellow fever relied mainly on clinical observations. In the 1930s, however, they devised indirect methods of visualizing the presence of the disease agent. Visceroctomy revealed the presence of acute cases of the disease. Mouse protection tests revealed past contacts with the agent. Taken together, these tests enabled the RF specialists to construct maps which indicated zones where the disease was endemic and to target specific anti-yellow fever campaigns based on selective elimination of the yellow fever vector, that is, the mosquito Aedes aegypti. In public health, like in the sciences, representation practices shape intervention.