According to the CDC, West Nile Virus is the leading cause of mosquito-borne disease in the U.S. Fortunately, most infected people (8 out of 10) do not feel sick. About 1 in 5 infected people develop a fever and other flu-like symptoms. About 1 out of 150 develop a serious, sometimes fatal illness such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord.) Dengue viruses are also spread to people through the bite of an infected mosquito. About one in four people infected with dengue will get sick. Symptoms can be mild or severe. The most common symptom of dengue is fever with any of the following: nausea, vomiting, rash, aches and pains (eye pain, typically behind the eyes, muscle, joint or bone pain.) About 1 in 20 people who get sick with dengue will develop severe dengue. Severe dengue can result in shock, internal bleeding and even death.