Brazil has reported the most cases of dengue fever in South America over last 30 years . High - risk cities are Recife , Fortaleza and Natal , they concluded . Even though three of the tournament cities pose a higher risk , according to the Brazilian Federal Government , the World Cup falls during a time of year that typically sees a 74 % reduction in dengue fever cases across the country . Many U.S. dengue cases involve travel to a dengue - endemic country . Group A and B , yellow fever , typhoid and malaria are also concerns during World Wars .
Brazil has reported the most cases of dengue fever in South America over last 30 years . High - risk cities are Recife , Fortaleza and Natal , they concluded . Many U.S. dengue cases involve travel to a dengue - endemic country . Group A and B , yellow fever , typhoid and malaria are also concerns during World Wars .