Last March I wrote a blog about increased numbers of cases of yellow fever in Brazil including close to Rio de Janeiro. This year Sao Paulo is seeing cases of yellow fever in monkeys and humans and vaccination is now recommended for travellers to all parts of Rio de Janeiro and Sao Paulo states including the urban areas. More than 180 laboratory-confirmed human cases of yellow fever (including 76 deaths) have been reported in the states of São Paulo (80 cases), Minas Gerais (> 45 cases), and Rio de Janeiro (15 cases) and in Distrito Federal (1 case) since July 2017. This is a big increase over normal numbers of cases. In addition, more than 250 confirmed cases of yellow fever in nonhuman primates have been reported since October 2017 throughout forested areas of São Paulo City and in expanding areas of São Paulo Metropolitan Region. Because of this many parks including the zoo and botanical gardens in São Paulo City are closed. Brazil has launched a massive vaccination campaign and hope to vaccinate almost 24 million people in the states of Rio de Janeiro and Sao Paulo in the hopes of preventing an urban outbreak.