It is strongly recommended that participants / visitors consult the website http://www.portalconsular.itamaraty.gov.br/vistos as well as the nearest Brazilian Consulate (click on the map) in advance of their trip to obtain official information on travelling to Brazil. The whole process of requiring a vista is the sole responsibility of each individual traveler.
It has been announced that Brazil will eliminate the tourist visa requirement for visitors from the US, Canada, Australia, and Japan, from June 17, 2019 on. Decreto 9.731
Here you find the list of nationalities that are exempt from this requirement. Those who do need visa should note that a tourist visa is sufficient for the conference attendance; for more information about Brazil, visit the official Brazilian Institute of Tourism website.