The mayor of Rio de Janeiro on Thursday warned residents against a potential outbreak of dengue fever as summer approaches in the Southern Hemisphere. \"Prevention is a task shared by the city hall and the population. Two thirds of dengue infections occur in people\'s own homes,\" Eduardo Paes said in a radio interview. Dengue fever is transmitted by Aedes Aegypti mosquitoes whose larvae usually grow in water containers. Therefore, residents were asked to empty containers to prevent mosquitoes\' growth. Paes said the country had sufficient health officials to check every house, but it was necessary for residents to \"take 10 minutes to check their own backyards.\" There is no vaccine against dengue fever, but Brazilian scientists are working on one. Paes also briefed his listeners on the government\'s preparations for the summer storms which hit Rio de Janeiro almost every year, adding that the city is still not fully prepared to withstand big floods, though many efforts have been made.