Persistent Emergence of Dengue

he disease dengue fever (DF; also known as break-bone fever, dandy fever, and by other names) can be caused by any of 4 viruses within the virus family Flaviviridae, genus Flavivirus, i.e., dengue virus types 1–4 (DENV-1–4). Dengue fever is a short-duration , nonfatal illness characterized by sudden onset of headache, retroorbital pain, and high fever, joint pain, and rash. Whereas uncomplicated DF usually is the case, the picture can be much darker than that. Through a mechanism known as immune enhancement, sequential infections with certain dengue viruses set the stage for a far more serious complication, dengue hemorrhagic fever (DHF) and dengue shock syndrome , so that having uncomplicated DF can presage having DHF (1). DHF is characterized by high fever, vascular perme-ability, bleeding, enlargement of the liver, and circulatory failure (dengue shock syndrome). In mild or moderate cases, signs and symptoms subside after the fever subsides, but in severe cases the patient's condition suddenly deteriorates , body temperature decreases, and the circulatory system begins to fail. The patient then may quickly go into shock and die within a day, or quickly recover, if volume therapy is instituted (2). Dengue viruses are transmitted from person to person or from monkey to monkey through infected female mosquitoes of the genus Aedes. The mosquito acquires the virus by taking a blood meal from an infected human, the principal amplifying host for these viruses, or from an infected monkey. Humans circulate these viruses in their blood (viremia) for 7 to 10 days after infection, allowing ample time for mosquitoes, often many mosquitoes, to feed and become infected. After an intrinsic incubation period of 1 week to 10 days, the mosquito is capable of transmitting the virus to a new host while blood feeding. During epidemics of dengue, attack rates may be 80%–90% in susceptible persons. Although, it is not usually recognized, more than half the people who are infected with a dengue virus may be asymptomatic, which would indicate a substantial underreporting of infections. These comprise a substantial number of people who may have been primed for more serious illness at a later date and are unaware of their situation. The global prevalence of dengue has increased substantially recently. with imported cases essentially everywhere tourists, business people, and military personnel travel, whether dengue is recognized there or not. More than 2 billion of the approximately 6.5 billion inhabitants of this planet are …