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Dengue-Fever Powered By Docstoc
					What and How much we know about Dengue fever?

Sajeeb Sarker

Dengue, again, is the issue; we suffer a lot and we forget about then. This happens just every single time. But, if we just try to know something about this – in as much details as possible, we can have a lot more chance to prevent it. And by knowing a little more about its types and diagnosis systems, we can increase the chance of preventing being misdiagnosed. Here are some information about Dengue that can be a lot helpful for both purposes, and for all people: Dengue fever is a disease caused by a family of viruses that are transmitted by mosquitoes. It is an acute illness of sudden onset that usually follows a benign course with headache, fever, exhaustion, severe joint and muscle pain, swollen glands (lymphadenopathy), and rash. The presence (the "dengue triad") of fever, rash, and headache (and other pains) are particularly characteristics of dengue. Dengue fever and dengue hemorrhagic fever (DHF) are acute febrile diseases caused by four closely related virus serotypes of the genus Flavivirus, family Flaviviridae. The geographical spread is similar to malaria. 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 Aedes aegypti (rarely Aedes albopictus) mosquito, which feeds during the day. Virus Classification Group: Group IV {(+) ssRNA} Family: Flaviviridae Genus: Flavivirus Species: Dengue Virus Dengue (pronounced DENG-gay) strikes people with low levels of immunity. Because it is caused by one of four serotypes of virus, it is possible to get dengue fever multiple times. However, an attack of dengue produces immunity for a lifetime to that particular serotype to which the patient was exposed. Dengue goes by other names, including "breakbone" or "dandy fever." Victims of dengue often have contortions due to the intense joint and muscle pain, hence the name breakbone fever. Slaves in the West Indies who contracted dengue were said to have dandy fever because of their postures and gait.


Dengue hemorrhagic fever is a more severe form of the viral illness. Manifestations include headache, fever, rash, and evidence of hemorrhage in the body. Petechiae (small red or purple blisters under the skin), bleeding in the nose or gums, black stools, or easy bruising are all possible signs of hemorrhage. This form of dengue fever can be life-threatening or even fatal. Dengue haemorrhagic fever (fever, abdominal pain, vomiting, bleeding) is a potentially lethal complication, affecting mainly children. Early clinical diagnosis and careful clinical management by experienced physicians and nurses increase survival of patients. Well, we’ll discuss it later.

How is dengue contracted?
The virus is contracted from the bite of a striped Aedes aegypti mosquito that has previously bitten an infected person. The mosquito flourishes during rainy seasons but can breed in water-filled flower pots, plastic bags, and cans yearround. One mosquito bite can inflict the disease. Again, dengue is transmitted by the bite of an Aedes mosquito infected with any one of the four dengue viruses. It occurs in tropical and sub-tropical areas of the world. Symptoms appear 3—14 days after the infective bite. Dengue fever is a febrile illness that affects infants, young children and adults. The virus is not contagious and cannot be spread directly from person to person. There must be a person-to-mosquito-to-another-person pathway.

What are the signs and symptoms of dengue?
After being bitten by a mosquito carrying the virus, the incubation period ranges from three to 15 (usually five to eight) days before the signs and symptoms of dengue appear. Dengue starts with chills, headache, pain upon moving the eyes, and low backache. Painful aching in the legs and joints occurs during the first hours of illness. The temperature rises quickly as high as 104° F (40° C), with relative low heart rate (bradycardia) and low blood pressure (hypotension). The eyes become reddened. A flushing or pale pink rash comes over the face and then disappears. The glands (lymph nodes) in the neck and groin are often swollen. Fever and other signs of dengue last for two to four days, followed by rapid drop in temperature (defervescence) with profuse sweating. This precedes a period with normal temperature and a sense of well-being that lasts about a day. A second rapid rise in temperature follows. A characteristic rash appears along with the


fever and spreads from the extremities to cover the entire body except the face. The palms and soles may be bright red and swollen. Symptoms range from a mild fever, to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, and rash. There are no specific antiviral medicines for dengue. It is important to maintain hydration. Use of acetylsalicylic acid (e.g. aspirin) and non steroidal anti-inflammatory drugs (e.g. Ibuprofen) is not recommended. Yet, we can have another look over the signs and symptoms of dengue for a little more information: This infectious disease is manifested by a sudden onset of fever, with severe headache, muscle and joint pains (myalgias and arthralgias—severe pain gives it the name break-bone fever or bonecrusher disease) and rashes. The dengue rash is characteristically bright red petechiae 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 diarrhea. Other symptoms include:
• • • • • •

fever; chills; constant headaches; bleeding from nose, mouth or gums; severe dizziness; and, loss of appetite.

Some cases develop much milder symptoms which can, when no rash is present, be misdiagnosed as influenza or other viral infection. Thus travelers from tropical areas may inadvertently pass on dengue in their home countries, having not been properly diagnosed at the height of their illness. Patients with dengue can pass on the infection only through mosquitoes or blood products and only 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 disease (the so-called "biphasic pattern"). Clinically, the platelet count will drop until the patient's temperature is normal. Cases of DHF also show higher fever, haemorrhagic phenomena, thrombocytopenia, and haemoconcentration. A small proportion of cases lead to dengue shock syndrome (DSS) which has a high mortality rate.


Dengue shock syndrome is defined as dengue hemorrhagic fever plus:
• • •

Weak rapid pulse, Narrow pulse pressure (less than 20 mm Hg) or, Cold, clammy skin and restlessness.

What is dengue hemorrhagic fever?
Here, we’ve spoken of dengue hemorrhagic fever several times; let’s take a little close look at this: The WHO definition of dengue haemorrhagic fever has been in use since 1975; all four criteria must be fulfilled: 1. Fever, bladder problem, constant headaches, severe dizziness and loss of appetite. 2. Hemorrhagic tendency (positive tourniquet test, spontaneous bruising, bleeding from mucosa, gingiva, injection sites, etc.; vomiting blood, or bloody diarrhea) 3. Thrombocytopenia (<100,000 platelets per mm³ or estimated as less than 3 platelets per high power field) 4. Evidence of plasma leakage (hematocrit more than 20% higher than expected, or drop in haematocrit of 20% or more from baseline following IV fluid, pleural effusion, ascites, hypoproteinemia)

In other words, dengue hemorrhagic fever (DHF) is a specific syndrome that tends to affect children under 10. It causes abdominal pain, hemorrhage (bleeding), and circulatory collapse (shock). DHF is also called Philippine, Thai, or Southeast Asian hemorrhagic fever and dengue shock syndrome.
DHF starts abruptly with high continuous fever and headache. There are respiratory and intestinal symptoms with sore throat, cough, nausea, vomiting, and abdominal pain. Shock occurs two to six days after the start of symptoms with sudden collapse, cool, clammy extremities (the trunk is often warm), weak pulse, and blueness around the mouth (circumoral cyanosis). In DHF, there is bleeding with easy bruising, blood spots in the skin (petechiae), spitting up blood (hematemesis), blood in the stool (melena), bleeding gums, and nosebleeds (epistaxis). Pneumonia is common, and inflammation of the heart (myocarditis) may be present.


Patients with DHF must be monitored closely for the first few days since shock may occur or recur precipitously. Cyanotic (bluish) patients are given oxygen. Vascular collapse (shock) requires immediate fluid replacement. Blood transfusions may be needed to control bleeding. The mortality, or death rate, with DHF is significant. It ranges from 6%-30%. Most deaths occur in children. Infants under a year of age are especially at risk of dying from DHF.

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 polymerase chain reaction (PCR) studies are available to confirm the diagnosis of dengue if clinically indicated.

How is dengue fever treated?
Because dengue is caused by a virus, there is no specific medicine or antibiotic to treat it. For typical dengue, the treatment is purely concerned with relief of the symptoms (symptomatic). Rest and fluid intake for adequate hydration is important. Aspirin and nonsteroidal anti-inflammatory drugs should be avoided. Acetaminophen (Tylenol) and codeine may be given for severe headache and for the joint and muscle pain (myalgia). The mainstay of treatment is supportive therapy. Increased oral fluid intake is recommended to prevent dehydration. Supplementation with intravenous fluids may be necessary to prevent dehydration and significant concentration of the blood if the patient is unable to maintain oral intake. A platelet transfusion is indicated in rare cases if the platelet level drops significantly (below 20,000) or if there is significant bleeding. The presence of melena may indicate internal gastrointestinal bleeding requiring platelet and/or red blood cell transfusion. Aspirin and non-steroidal anti-inflammatory drugs should be avoided as these drugs may worsen the bleeding tendency associated with some of these infections. Patients may receive paracetamol preparations to deal with these symptoms if dengue is suspected.


Emerging treatments Emerging evidence suggests that mycophenolic acid and ribavirin inhibit dengue replication. Initial experiments showed a fivefold increase in defective viral RNA production by cells treated with each drug. In vivo studies, however, have not yet been done.

How can dengue fever be prevented?
Vaccine development 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 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. Thai researchers are testing a dengue fever vaccine on 3,000–5,000 human volunteers after having successfully conducted tests on animals and a small group of human volunteers. And, a number of other vaccine candidates are entering phase I or II testing. Mosquito control A field technician looking for larvae in standing water containers during the 1965 Aedes aegypti eradication program in Miami, Florida. In the 1960s, a major effort was made to eradicate the principal urban vector mosquito of dengue and yellow fever viruses, Aedes aegypti, from southeast United States. Primary prevention of dengue mainly resides in mosquito control. There are two primary methods: larval control and adult mosquito control. In urban areas, Aedes mosquitos breed on water collections in artificial containers such as plastic cups, used tires, broken bottles, flower pots, etc. Continued and sustained artificial container reduction or periodic draining of artificial containers is the most effective way of reducing the larva and thereby the aedes mosquito load in the community. Larvicide treatment is another effective way of control the vector larvae but the larvicide chosen should be long lasting and preferably have World Health Organization clearance for use in drinking water. There are some very effective insect growth regulators (IGR`s) available which are both safe and long alasting e.g. pyriproxyfen. For reducing the adult mosquito load, fogging with insecticide is somewhat effective. Prevention of mosquito bites is another way of preventing disease. This can be achieved either by personal protection or by using mosquito nets. In 1998, scientists from the Queensland Institute of Research in Australia and Vietnam's


Ministry of Health introduced a scheme that encouraged children to place a water bug, the crustacean Mesocyclops, in water tanks and discarded containers where the Aedes aegypti mosquito was known to thrive. This method is viewed as being more cost-effective and more environmentally friendly than pesticides, though not as effective, and requires the ongoing participation of the community. Personal protection Personal prevention consists of the use of mosquito nets, repellents containing NNDB or DEET, covering exposed skin, use of DEET-impregnated bednets, and avoiding endemic areas. Potential antiviral approaches In cell culture experiments and mice Morpholino antisense oligos have shown specific activity against Dengue virus. The yellow fever vaccine (YF-17D) is a vaccine for a related Flavivirus, thus the chimeric replacement of yellow fever vaccine with dengue has been often suggested but no full scale studies have been conducted to date. In 2006, a group of Argentine scientists discovered the molecular replication mechanism of the virus, which could be attacked by disruption of the polymerase's work. We can think of prevention in different words as: The transmission of the virus to mosquitoes must be interrupted to prevent the illness. To this end, patients are kept under mosquito netting until the second bout of fever is over and they are no longer contagious. The prevention of dengue requires control or eradication of the mosquitoes carrying the virus that causes dengue. In nations plagued by dengue fever, people are urged to empty stagnant water from old tires, trash cans, and flower pots. Governmental initiatives to decrease mosquitoes also help to keep the disease in check but have been poorly effective. Wear long pants and long sleeves. For personal protection, use mosquito repellant sprays that contain DEET when visiting places where dengue is endemic. Limiting exposure to mosquitoes by avoiding standing water and staying indoors two hours after sunrise and before sunset will help. The Aedes aegypti mosquito is a daytime biter with peak periods of biting around sunrise and sunset. It may bite


at any time of the day and is often hidden inside homes or other dwellings, especially in urban areas. There is currently no vaccine available for dengue fever. There is a vaccine undergoing clinical trials, but it is too early to tell if it will be safe or effective.

What is the outcome with typical dengue?
Typical dengue does not result in death. It is fatal in less than 1% of cases. The acute phase of the illness with fever and myalgias lasts about one to two weeks. Convalescence is accompanied by a feeling of weakness (asthenia), and full recovery often takes several weeks.

Dengue : The ‘Evil Spirit’...
The origins of the word dengue are not clear, but one theory is that it is derived from the Swahili phrase "Ka-dinga pepo", which describes the disease as being caused by an evil spirit. The Swahili word "dinga" may possibly have its origin in the Spanish word "dengue" (fastidious or careful), describing the gait of a person suffering dengue fever or, alternatively, the Spanish word may derive from the Swahili. It may also be attributed to the phrase meaning "Break bone fever", referencing the fact that pain in the bones is a common symptom. Outbreaks resembling dengue fever have been reported throughout history. The first definitive case report dates 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 deciphered only in the 20th century. Population movements during World War II spread the disease globally. In 2007 replication mechanism of the virus was interrupted by interception of the viral protease, and currently a project to identify new protease interception mechanisms of the whole familly of the virus has been launched (Dengue virus belong to the familly Flaviviridae, which includes among others HCV, West Nile and Yellow fever viruses). The software and information about the project can be found at the World Community Grid web site.

What areas are at high risk for contracting dengue fever?
Dengue is prevalent throughout the tropics and subtropics. Outbreaks have occurred in the Caribbean, including Puerto Rico, the U.S. Virgin Islands, Cuba, and Central America. Cases have also been imported via tourists returning from


areas with widespread dengue, including Tahiti, the South Pacific, Southeast Asia, the West Indies, India, and the Middle East. Dengue fever is common and may be increasing in Southeast Asia. Thailand, Vietnam, Singapore, and Malaysia have all reported an increase in cases. According to the World Health Organization, there are an estimated 50 million cases of dengue fever with 500,000 cases of dengue hemorrhagic fever requiring hospitalization each year. Nearly 40% of the world's population lives in an area endemic with dengue. Though not that much epidemic as other places, yet, Bangladesh is not even a fresher for dengue. A lot people have suffered and have been suffering, and a considerable number of people have already died. In this circumstance, we should treat the issue of dengue as a highly priorative, and knowing about dengue as much as possible is a must to make prevention against it.
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Acosta, Dalia (2006-09-12). "War on Mosquitoes Continues During Global Summit", Inter Press Service.


Manson's Tropical Diseases Mandell's Principles and Practices of Infection Diseases Cecil Textbook of Medicine The Oxford Textbook of Medicine Harrison's Principles of Internal Medicine Theiler, Max and Downs, W. G. 1973. The Arthropod-Borne Viruses of Vertebrates: An Account of The Rockefeller Foundation Virus Program 1951-1970. Yale University Press. 14. Downs, Wilbur H., et al. 1965. Virus diseases in the West Indies. Special edition of the Caribbean Medical Journal, Vol. XXVI, Nos. 1-4, 1965. 15. Earle, k. Vigors. 1965. "Notes on the Dengue epidemic at Point Fortin." The Caribbean Medical Journal, Vol. XXVI, Nos. 1-4, pp. 157-164. 16. Hill, A. Edward. 1965. "Isolation of Dengue Virus from a Human Being in Trinidad." Virus diseases in the West Indies. The Caribbean Medical Journal, Vol. XXVI, Nos. 1-4, pp. 83-84; "Dengue and Related Fevers in Trinidad and Tobago." Ibid, pp. 91-96. Courtesy: Centers for Disease Control and Prevention, Public Health Image Library.




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