Yellow Fever spreads in Brazil...get your vaccine before travel.

CDC / Yellow Fever in Brazil
Center for Disease Control and Prevention: update December 19, 2011

Current Situation

Yellow fever is a risk for travelers to most areas of Brazil, except coastal regions. During 2009, an outbreak of yellow fever, including a number of deaths, occurred in parts of southeastern Brazil that had not been affected by yellow fever for many years.

In response, the Brazil Ministry of Health has gradually expanded the list of municipalities for which yellow fever vaccination is recommended in the four southeastern states of São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul
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Globally, yellow fever occurs in sub-Saharan Africa and tropical South America and is spread to people through the bite of infected mosquitoes. Symptoms can include sudden onset of fever, chills, headache, backache, nausea, and vomiting.

Yellow Fever Risk Areas in Brazil
Currently, Brazil and CDC recommend yellow fever vaccination for travelers to the following states:

All areas of Acre, Amapá, Amazonas, Distrito Federal (including the capital city of Brasília), Goiás, Maranhão, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Pará, Rondônia, Roraima, and Tocantins.
Other designated areas of the following states: Bahia, Paraná, Piauí, Rio Grande do Sul, Santa Catarina, and São Paulo. Vaccination is also recommended for travelers visiting Iguassu Falls.

Source: CDC / Yellow Fever in Brazil, update