Paris: Three Brazilian host cities -- Fortaleza, Natal and Recife -- are at higher risk than the other nine of a dengue fever outbreak during the World Cup, scientists said on Saturday.

A German football fan
Watch It! A German football fan. Pic For Representation.

In absolute terms, the risk is low in all Cup venues, but comparatively greater in the three northeastern cities and authorities should beef up steps to prevent an outbreak, they said.

A potentially dangerous fever caused by a virus for which there is no vaccine or cure, dengue is transmitted by the Aedes aegypti mosquito when it takes a blood meal.

Doctors last year sounded the alarm over dengue at the June 12-July 13 tournament. The disease is endemic in Brazil, which is expected to lure hundreds of thousands of football visitors.