The Centers for Disease Control and Prevention reports that the disease—the most common cause of fever in travelers returning from Central America and the Caribbean—is also active in other countries in the region and South America, including Argentina, Brazil, Colombia, Costa Rica, El Salvador, French Guiana, Guadeloupe, Honduras, and Peru. Cases of dengue fever have been on the rise around the world since 2009, including parts of Africa, the South Pacific, and the Middle East. The CDC provides a map of dengue risk areas. The disease is rare in the U.S., but it has been reported recently in Texas, and is expected to become more common as the climate warms.

Usually symptoms of dengue fever are mild. They can include, the eponymous fever usually four to seven days after a mosquito bite (onset of symptoms can range from three to 14 days), severe headache, pain behind the eyes, joint and muscle pain, rash, and nausea and/or vomiting. In severe cases, however, the disease can lead to potentially fatal dengue hemorrhagic fever (DHF), which can cause bleeding from the nose, gums, or under the skin causing purple bruises. About 1 percent of dengue fever cases progress to DHF, and those who have had dengue fever before are at greater risk of such complications. Even more severe is the massive bleeding and shock caused by dengue shock syndrome, which is most common in children.