The Ministry of Public Health has alerted residents in the DR to take precautions to avoid being infected by the dengue fever virus. The Ministry is also extensively making known the symptoms of the illness so that those affected may visit hospital centers and prevent severe conditions. Dengue Fever is primarily a viral infection transmitted by mosquito bites in residential areas. Dominican medical authorities say that more than 1,000 cases have been reported, and eight persons have died due to delays in attending the illness. In Puerto Rico, some 10,000 cases have been reported. The World Health Organization says there are approximately 50 million cases of dengue annually. The Ministry alerts that the mosquito does not discriminate by social classes. The virus is spread by mosquito bites. The mosquitoes are most active during the day, especially around dawn and dusk, and are frequently found in or around human habitations. The illness is flulike and characterized by sudden onset, high fever, severe headaches, joint and muscle pain, and rash. The rash appears 3-4 days after the onset of fever. Since there is no vaccine or specific treatment available, prevention is important. The Ministry of Health is recommending persons to remove flower vases, cans and other recipients in which mosquitoes could breed. According to the Center for Disease Control of the U.S. Government, in the Caribbean islands, low level transmission occurs throughout the year in most tourist-oriented islands. Seasonal and sporadic epidemics with higher transmission rates also frequently occur. The risk of infection is small for most travelers except during periods of epidemic transmission. CDC says that to reduce mosquito bites, travelers should remain in well-screened areas, use mosquito nets and wear clothes that cover most of the body. Travelers should also take insect repellent with them to use on any exposed areas of the skin. The most effective repellent is DEET), an ingredient in most insect repellents that should be used according to label directions and sparingly on children.