1793 Philadelphia yellow fever epidemic with slaves, arrived from Cap Français, Saint-Domingue. The 2,000 immigrants were fleeing the slave revolution in the north of the island. They crowded the port of Philadelphia, where the first yellow fever epidemic in 30 years began in the city in August. It is likely that the refugees and ships carried the yellow fever virus and mosquitoes. It is transmitted during mosquito bites. The mosquitoes easily breed in small amounts of standing water. The medical community and others in 1793 did not understand the role of mosquitoes in the transmission of yellow fever and other diseases. Physicians and other survivors
Yellow fever outbreaks, fractional dosing of the vaccine is being considered as a dose-sparing strategy to maximize limited vaccine supplies. Fractional dose yellow fever vaccination refers to administration of a reduced volume of vaccine dose, which has been reconstituted as per manufacturer recommendations. The first practical use of fractional dose yellow fever vaccination was in response to a large yellow fever outbreak in the Democratic Republic of the Congo in mid-2016. In March 2017, WHO launched a vaccination campaign in Brazil with 3.5 million doses from an emergency stockpile. In March 2017 the WHO recommended vaccination for travellers to certain parts of