Yellow fever is a serious flu-like disease spread by mosquito
bites. It is not curable but can be prevented with a vaccine,
using insect repellent, and wearing protective clothing. The
illness ranges in severity from fever to liver damage to possible
death.
A yellow fever outbreak that began a year and a half ago in
Brazil is spreading further, with additional cases since last
July in the Brazilian states of Sáo Paulo, Minas Gerais and Rio
de Janeiro, plus several cities in Bahia State.
The World Health Organization began recommending yellow fever
vaccination for all travelers and residents of these areas in
January, but since then, 10 travelers have contracted the
disease—all unvaccinated—and four died.