Brazil, with 1.4 million reported cases of dengue fever in 2013 and the world's largest outbreak of the disease, is about to welcome millions of visitors from all over the world to its World Cup soccer tournament. Authorities are concerned tourists could carry the mosquito-borne virus back and spread it in their home countries.
A study published by Lancet Infectious Diseases concluded the threat is greatest in northeastern coast cities of Natal, Fortaleza and Recife. Rio de Janeiro, Belo Horizonte, Salvador and Manaus were identified as "medium risk" locations.
The tournament will begin June 12 and will be played for a month in 12 Brazilian cities.
Dengue fever is caused by several viruses. An infection causes rash, fever and joint pain; a second variation, dengue hemorrhagic fever, can follow the first and can be fatal.
Cases in Brazil dropped sharply in the summer of 2013 due to dry weather conditions, reducing the Aedes mosquito population.
A commentary by Australian scientists suggested there would be few cases of the virus traveling home with tourists, since few visitors from hot and wet tropical countries, where Aedes mosquitoes thrive, could afford the trip to Brazil.