the prefecture of rio de janeiro offers vaccines and guidelines for dengue through the portal rio contra a dengue, accessible on this link - it also lists here, where to go in case of suspected infection in a number of city neighborhoods - smaller cities and popular tourist destinations near rio de janeiro such as angra dos reis, cabo frio, and nova friburgo, are also included on the list.

visitors planning visits to the rain forest, favelas, lagoa and other areas where there could be stagnant water should use insect repellant spray - as additional precautions, visitors can wear long sleeves, sleep under bug nets, use air conditioning inside, spray indoor friendly insecticide around accomodations and wear clothing treated with permethrin.

outbreaks of dengue fever kill people in rio every year, and the city is constantly running educational campaigns against the disease - zika virus is a condition currently affecting over 45 countries around the globe and Brazil is active in formulating solutions in the international community -  Here is an article by the brazilian government about Zika, dengue and chikungunya containing vital information for prevention and recognition of those diseases.