Visa information is given on the ICM web site. In short, visas are required for citizens of the USA, Canada, India, and most Asian and African countries. Visas are not required for most European and Central/South American citizens. The initial visa application form (you may have to accept the SSL certificate) is on the web, but ultimately you (or someone—a friend, proxy, broker, …) must present the application in person at a Brazilian consulate (not by mail). Map of US consulates. Please see the ICM and Brazilian web pages.
Sponsored by the TeX Users Group, DANTE e.V., ICM'18, and individual donors. Thanks to all. New sponsors are greatly appreciated, as is mentioning the conference to colleagues and in any other contexts.
Contacting the organizers: