Dengue fever has been a worldwide concern since the 1960s. Many prominent tourist sites in the Caribbean (including Puerto Rico), Central and South America, Southeast Asia, and the Pacific Islands are affected by the illness. In addition, there is evidence that it is becoming established in parts of Africa for the first time. Dengue affects more than 100 million people per year, and estimates indicate that there are now about 50 million cases per year worldwide. The disease is found from the tropics to the temperate zones around the world, but it is especially prevalent in tropical regions where the climate allows for its reproduction within the vector (the mosquito). There are four types of dengue virus: dengue 1, 2, 3, and 4. They all belong to the genus Dengue virus and family Flaviviridae. Symptoms include high fever, headache, muscle pain, nausea, vomiting, diarrhea, chills, cough, and skin rash. Some patients may need hospitalization if their conditions worsen. In order to prevent the spread of dengue, health officials recommend reducing exposure to the virus by avoiding places with large numbers of mosquitoes (such as backyard pools) and using insecticide treated clothing and tents at home and while traveling in endemic areas. As part of global efforts to control the spread of dengue, countries report annual incidences of the disease to the World Health Organization.