Individuals with dengue generally have a history of either living in or travelling recently to areas that have been denoted as endemic . The incubation period for the condition is 3-14 days.
Symptoms that occur two weeks after departure of the individual from an endemic area may not be due to the dengue virus.
Most patients experience erythematous mottling of the skin, chills and facial flushing. Facial flushing can be regarded as one of the most specific indicators of dengue fever. The chills may last for 2-3 days. Maculopapular rash and nonspecific febrile syndrome is often seen in children that are younger than 15 years of age.
Standard cases of dengue begin with onset of fever, chills, aching of the back, head, extremities and other symptoms . The fever generally lasts for 2-7 days and so fever longer than 10 days may not be due to dengue.
The signs and symptoms of dengue fever are nonspecific . Therefore attempting a laboratory confirmation of the dengue infection is vital. Criteria to be met in the laboratory for diagnosis to be confirmed include:
The following laboratory tests equally have to be performed:
Dengue fever is usually a self-limited illness. As there is presently no antiviral drug available, treatment is supportive, with analgesics, fluid replacement, and bed rest.
Dengue fever is caused by the DENV (dengue virus). This virus is a single-stranded RNA virus of the family Flaviviridae and genus Flavivirus. The type specific virus is yellow fever . The dengue virus has 4 stereotypes that are antigenically distinct. Each of the stereotypes have several different genotypes and disease severity is affected by the sequence of infection with different serotypes.
An important risk factor for infection is living in endemic areas of the tropics where the vector mosquito thrives. The explosive global population growth and poorly planned urbanization is what brings the human host and mosquito close to each other.
Increase in air travel also makes it easy for infectious diseases to be transported between different groups.
In the U.S dengue occurs principally in travellers who have just returned from areas marked as endemic. According to the CDC, 244 confirmed cases of travel related dengue were reported in the U.S within 2006 to 2008.
Over the past 20 years, there has been an increase in the cases of Dengue amongst returning U.S travellers. The condition is also responsible for majority of febrile illnesses in individuals returning from South America, Asia and the Caribbean .
500,000 cases of dengue hemorrhagic fever and 50-100 million cases of dengue fever occur worldwide each year with an approximated 22,000 deaths recorded yearly too. 40% of the world’s population are at risk of dengue infection (an estimated 2.5-3 billion people spread across 112 tropical and subtropical countries around the world).
The only continents where dengue transmission is not experienced are Antarctica and Europe. The WHO rates dengue as the most important viral disease transmitted by mosquito in the world. Dengue has continued to pose a challenge to world health as it has increased 30 fold over the past 30 years.
As mentioned above, dengue fever is a mosquito-borne viral disease that is caused by one of four dengue virus types . Homotypic immunity is conferred on an individual after infection by one type of this virus. There is also brief period of partial heterotypic immunity. It is possible for several serotypes to be in circulation in the event of an epidemic.
Dengue fever develops like majority of bacterial and viral illnesses. Fever sets in on the third day of illness and may last for 5-7 days. It abates with the end of viremia. In children, the fever is intermittent, abating for a day before recurring. This is a pattern that is known as saddleback fever. The saddleback fever is more commonly seen in dengue hemorrhagic fever cases.
There are not yet any vaccines to prevent infection and the most effective protective measures are those that avoid mosquito bites.
Dengue fever is transmitted by the A. aegypti mosquito. The dengue virus is of 5 types. When an individual is infected with one type, he or she gets lifelong immunity to that type. Infection also brings immunity to the other virus forms, albeit temporary . Infection by another type of the virus after an earlier case leads to an increased risk of severe complications.
There are no commercially available vaccines. Therefore prevention is achieved by reducing or destroying the mosquito habitat and also limiting the exposure of individuals to bites.
Dengue vascualopathy or Dengue hemorrahgic fever brings about vascular leakage in patients and this often results in serous effusions and hemoconcentration which may lead to a collapse of the circulatory system. This happens in conjuction with severe hemorrhagic complications leading to dengue shock syndrome, a condition with greater risk of fatality.
Individuals who have suffered dengue fever in the past should avoid mosquito bites through the use of repellants and other domestic vector control techniques especially when travelling to areas that are endemic . This is because such individuals are at risk of developing the dengue shock syndrome or dengue hemorrhagic fever if they get infected with a different dengue strain in the future.