Dangers and annoyances Bilharzia (schistosomiasis) is found throughout Grande-Terre and in much of Basse-Terre, including Grand etang lake. The main method of prevention is to avoid swimming or wading in fresh water.There have been recent outbreaks of dengue fever, aka breakbone fever because of the joint and muscle pain it inflicts. It’s potentially fatal. Health professionals advise using insect repellent containing DEET or Picaridin on exposed skin. Dengue outbreaks tend to occur wherever there’s standing water – more frequent in cities than in the countryside.