This article is about the tropical disease. For the article about the California-based psychedelic rock band, see Dengue Fever (band) .
and '''dengue
Hemorrhagic Fever ''' (DHF) are acute febrile diseases, found in the tropics, with a geographical spread similar to
Malaria . Caused by one of four closely related virus
Serotype s of the genus ''
Flavivirus '', family
Flaviviridae , each serotype is sufficiently different that there is no cross-protection and epidemics caused by multiple serotypes (hyperendemicity) can occur. Dengue is transmitted to humans by the
Mosquito ''
Aedes Aegypti '' (rarely ''
Aedes Albopictus '').
The disease is manifested by a sudden onset of
Fever , with severe headache, joint and muscular pains (
Myalgia s and
Arthralgia s — severe pain gives it the name ''break-bone fever'') and
Rash es; the dengue rash is characteristically bright red
Petechia and usually appears first on the lower limbs and the chest - in some patients, it spreads to cover most of the body. There may also be
Gastritis with some combination of associated abdominal pain,
Nausea ,
Vomiting or
Diarrhoea .
Some cases develop much milder symptoms, which can, when no rash is present, be misdiagnosed as a flu or other viral infection. Thus, travelers from tropical areas may inadvertently pass on dengue in their home countries, having not being properly diagnosed at the height of their illness. Patients with dengue can only pass on the infection through mosquitoes or blood products while they are still febrile.
The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the trailing end of the fever (the so-called "biphasic pattern"). Clinically, the
Platelet count will drop until the patient's temperature is normal.
Cases of DHF also shows higher fever, haemorrhagic phenomena,
Thrombocytopenia and haemoconcentration. A small proportion of cases leads to dengue shock syndrome (DSS) which has a high mortality rate.
The diagnosis of dengue is usually made clinically. The classic picture is high fever with no localising source of infection, a petechial rash with
Thrombocytopenia and relative
Leukopenia .
Serology and
PCR (polymerase chain reaction) studies are available to confirm the diagnosis of dengue if clinically indicated.
The mainstay of treatment is supportive therapy. The patient is encouraged to keep up oral intake, especially of oral fluids. If the patient is unable to maintain oral intake, supplementation with
Intravenous Fluids may be necessary to prevent dehydration and significant hemoconcentration. A platelet
Transfusion is indicated if the platelet level drops significantly.
The first epidemics occurred almost simultaneously, in Asia, Africa, and North America in the
1780s . The disease was identified and named in
1779 . A global
Pandemic began in Southeast Asia in the
1950s and by
1975 DHF had become a leading cause of death among children in many countries in that region. Epidemic dengue has become more common since the
1980s - by the late
1990s , dengue was the most important mosquito-borne viral disease affecting humans after
Malaria , there being around 40 million cases of dengue fever and several hundred thousand cases of dengue hemorrhagic fever each year. In
February 2002 there was a serious outbreak in
Rio De Janeiro , affecting around one million people but only killing sixteen.
Significant outbreaks of dengue fever tend to occur every five or six years. There tend to remain large numbers of susceptible people in the population despite previous outbreaks because there are four different strains of the dengue virus and because of new susceptible individuals entering the target population, either through childbirth or immigration.
There is significant evidence, originally suggested by S.B. Halstead in the 1970s, that
Dengue Hemorrhagic Fever is more likely to occur in patients who have secondary infections by serotypes different from the primary infection - in a process known as
Antibody-dependent Enhancement (ADE).
In
Singapore , there are about 4000-5000 reported cases of dengue fever or dengue haemorrhagic fever every year. In the year
2003 , there were 6 deaths from dengue shock syndrome. It is believed that the reported cases of dengue are an underrepresentation of all the cases of dengue as it would ignore subclinical cases and cases where the patient did not present for medical treatment. With proper medical treatment, the mortality rate for dengue can therefore be brought down to less than 1 in 1000.
There is no commercially available
Vaccine for the dengue flavivirus. However, one of the many ongoing vaccine development programs is the Pediatric Dengue Vaccine Initiative (PDVI
{Link without Title} ) which was set up in 2003 with the aim of accelerating the development and introduction of dengue vaccine(s) that are affordable and accessible to poor children in endemic countries.
Primary prevention of dengue mainly resides in eliminating or reducing the mosquito vector for dengue. Initiatives to eradicate pools of standing water (such as in flowerpots) have proven useful in controlling mosquito borne diseases. Promising new techniques have been recently reported from
Oxford University on rendering the Aedes mosquito pest sterile.
Personal prevention consists of the use of
Mosquito Net s,
Repellents and avoiding endemic areas.
In cell culture experiments
Morpholino antisense oligos have shown specific activity against Dengue virus
{Link without Title} .
In 2002 the Swiss pharma company
Novartis and the Singapore Economic Development board created the Novartis Institute for Tropical Diseases
(NITD) . NITD is a public-private partnership that researches neglected tropical disease. NITD's dengue unit is researching anti-viral drug discovery to treat or prevent dengue fever.
Recent dengue outbreaks in South East Asia:
- Philippines ([http://news.inq7.net/breaking/index.php?index=2&story_id=53192 January - October 2005]) 21,537 cases with 280 dead.
- Thailand ( May 2005 ) 7200 infected. At least 12 dead.
- Indonesia ( 2004 ) 80,000 infected with 800 deaths.
- Malaysia ( January 2005 ), 33,203 cases.
- Singapore (2005), At least 13 deaths, ( 2004 ), 9460 cases, (2003), 4788 cases.
- Australia {Link without Title} 15 March 2006, 2 Confirmed Cases at Gordon Vale, Cairns, Queensland.
As of
September 2005 , Singapore reported a significant rise in the number of dengue cases - about 9000 in the year to date so far, about double the rate for the same period in 2004. It is even possible to have more than 500 cases per week. The large increase in dengue cases has caused hospitals to cancel some elective surgery due to the need to allocate more beds for dengue patients.
The term "dengue" is a Spanish attempt at the Swahili phrase "''ki denga pepo''", meaning "''cramp- like seizure caused by an evil spirit''". It emerged during a Caribbean outbreak in 1827-1828.
Outbreaks resembling dengue fever have been reported throughout history. The first case report dates back from 1789 and is attributed to
Benjamin Rush , who coined the term "breakbone fever" (because of the symptoms of
Myalgia and
Arthralgia ). The viral etiology and the transmission by mosquitoes were only deciphered in the 20th century. The socioeconomic impact of
World War II resulted in increased spread globally.
