At least two fatal cases of yellow fever have been confirmed in the São Paulo Metropolitan Area as of January 6. They are the first two deaths in the city since the disease was detected in the area in October 2017; it is believed that the victims contracted the disease while visiting the suburb of Mairiporã over the Christmas holiday period. A third human case has also been reported. Residents of São Paulo state, and individuals traveling to Mairiporã, Guarulhos, and Itapecerica da Serra specifically, are being urged to get vaccinated against yellow fever if they have not already done so.
Brazil suffered from a widespread yellow fever outbreak from December 2016 to June 2017, during which period hundreds of cases were reported. The outbreak notably spread to urban areas of the southeastern states of Rio de Janeiro and São Paulo. Prior to 2017, yellow fever outbreaks had not occurred in urban areas of Brazil since 1942.
Symptoms of yellow fever - a mosquito-borne disease - generally appear within three to six days following infection and include fever, chills, muscle and back pain, vomiting, headaches, and, in more serious cases, hemorrhaging, and organ failure. The yellow fever vaccine should be administered at least ten days prior to travel to an affected zone to be fully effective. The vaccine provides life-long immunity.
Individuals in or planning travel to Brazil are advised to stay abreast of local epidemiological developments, consult their doctor regarding vaccination options, and continue to protect themselves against insects due to the presence of various other mosquito-borne diseases (dengue fever, chikungunya, Zika virus, etc.), e.g. by wearing covering clothing, using insect repellent, and sleeping in screened-in and/or air conditioned rooms.
A full list of zones where the World Health Organization (WHO) recommends vaccination is available here.