Dengue fever is a disease caused by a virus. This virus lives in mosquitoes. The virus can cause fever, headaches, rashes, and pain throughout the body. Most cases of dengue fever are mild and go away on their own after about a week. When a mosquito infected by the dengue virus bites a person, the person can get affected by dengue fever. The virus can't spread directly from person to person. In rare cases, dengue fever can lead to a more serious form of the disease called dengue haemorrhagic fever (DHF). DHF can be life-threatening and needs to be treated right away. It can be fatal sometimes.