Dengue Scare

Background information on dengue/DHF: The World Health Organization considers dengue to be the most important vector-borne viral disease, potentially affecting 2.5 billion people in more than 100 tropical and sub-tropical countries throughout the world. Current estimates suggest that up to 50 to 100 million dengue cases occur annually, in addition to 500,000 cases of the more serious dengue hemorrhagic fever (DHF). DHF has a 5% case-fatality rate in many countries, with most fatalities occurring among children and young adults. The principal vector for dengue is the Aedes aegypti mosquito.

Symptoms of dengue/DHF:
Classical dengue fever, also known as break bone fever, is characterized by a sudden onset of fever, headache, sore muscles and joints, with occasional nausea/vomiting and rash; these symptoms may persist for several days.
Dengue hemorrhagic fever (DHF) is a much more serious illness mainly affecting children and young adults and is a leading cause of childhood mortality in several Asian countries. Symptoms include a sudden onset of fever and hemorrhagic manifestations that result in significant fluid loss and may lead to shock--dengue shock syndrome. Five percent of DHF cases are fatal. A prior infection with one of the four dengue viruses results in a greater probability of contracting DHF.
Humans acquire dengue viruses from bites of infective female Aedes aegypti mosquitoes; the mosquitoes become infected, and remain so for the rest of their life, by feeding on infected human blood. An infected person has the virus circulating in them for 2-7 days, about the time he/she experiences fever. It is during this period of time that the mosquito may acquire the dengue virus through blood feeding or probing. The blood meal provides essential proteins for the females developing eggs.
No vaccine currently exists for dengue and it may be several years before one is available due to the difficulty in developing one vaccine effective against all four dengue viruses. It is essential that the vaccine protect against all four viruses because vaccination against only one or two could potentially increase the risk of more serious illness for people exposed to one of the other viruses. The dengue virus is a single-stranded RNA virus, polyhedral in shape, referred to as a flavi virus, from the Family Flaviviridae and Genus Flavivirus. The yellow fever virus is also a Flavivirus.

History of dengue/DHF:
The earliest reports of dengue fever epidemics date back to 1779-1780 in Asia, Africa and North America, indicating a widespread tropical distribution of Ae. aegypti during the past 200 years. After World War II, a global dengue pandemic began in Southeast Asia. This pandemic intensified in the Americas during the 1980s with outbreaks in Caribbean and Latin American countries including Venezuela, Colombia, Brazil, French Guiana, Suriname, and Puerto Rico. More recently, outbreaks of dengue have occurred in Brazil, Puerto Rico and Southeast Asia and in the western Pacific, including Vietnam, Singapore, Cambodia, Philippines, Malaysia, and Fiji. Prior to 1970, DHF epidemics had occurred in 9 countries in the world; by 1995 that number increased more than four-fold. At present India and Pakistan are also experiencing a dengue outbreak after the recent monsoon season.