Yellow fever Brazil. In March 2018, Brazil shifted its policy and announced it planned to vaccinate all 77.5 million currently-unvaccinated citizens by April 2019. Some countries in Asia are theoretically in danger of yellow fever epidemics (mosquitoes with the capability to transmit yellow fever and susceptible monkeys are present), although the disease does not yet occur there. To prevent introduction of the virus, some countries demand previous vaccination of foreign visitors if they have passed through yellow fever areas. Vaccination has to be proved by the production of a vaccination certificate which is valid 10 days after the vaccination and lasts for
1793 Philadelphia yellow fever epidemic vector of the 1793 plague in Philadelphia (and other Atlantic ports) was the British merchant ship "Hankey", which had fled the West African colony of Bolama (an island off West Africa, present day Guinea-Bissau) the previous November, trailing yellow fever at every port of call in the Caribbean and eastern Atlantic seaboard. See: "The Ship of Death: The Voyage That Changed the Atlantic World". After two weeks and an increasing number of fever cases, Dr. Benjamin Rush, a doctor's apprentice during the city's 1762 yellow fever epidemic, saw the pattern; he recognized that yellow fever had returned. Rush alerted his