What and How Much We Know About Dengue Fever

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What and How much we know about Dengue fever? By: 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
  What and How much we know about Dengue fever? By: Sajeeb SarkerDengue, again, is the issue; we suffer a lot and we forget about then. This happens just every singletime. But, if we just try to know something about this  in as much details as possible, we can have a lotmore chance to prevent it. And by knowing a little more about its types and diagnosis systems, we canincrease the chance of preventing being misdiagnosed. Here are some information about Dengue thatcan 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 abenign 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 (andother 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 differentthat there is no cross-protection and epidemics caused by multiple serotypes (hyperendemicity) canoccur. Dengue is transmitted to humans by the Aedes aegypti (rarely Aedes albopictus) mosquito, whichfeeds 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 fevermultiple times. However, an attack of dengue produces immunity for a lifetime to that particularserotype 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, hencethe name breakbone fever. Slaves in the West Indies who contracted dengue were said to have dandyfever 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 theskin), 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. Earlyclinical diagnosis and careful clinical management by experienced physicians and nurses increasesurvival 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 aninfected 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 transmittedby the bite of an Aedes mosquito infected with any one of the four dengue viruses. It occurs in tropicaland sub-tropical areas of the world. Symptoms appear 314 days after the infective bite. Dengue feveris 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-personpathway.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 occursduring the first hours of illness. The temperature rises quickly as high as 104° F (40° C), with relative lowheart rate (bradycardia) and low blood pressure (hypotension). The eyes become reddened. A flushingor pale pink rash comes over the face and then disappears. The glands (lymph nodes) in the neck andgroin are often swollen. Fever and other signs of dengue last for two to four days, followed by rapiddrop in temperature (defervescence) with profuse sweating. This precedes a period with normaltemperature and a sense of well-being that lasts about a day. A second rapid rise in temperaturefollows. A characteristic rash appears along with thefever and spreads from the extremities to cover the entire body except the face. The palms and solesmay be bright red and swollen. Symptoms range from a mild fever, to incapacitating high fever, withsevere headache, pain behind the eyes, muscle and joint pain, and rash. There are no specific antiviralmedicines for dengue. It is important to maintain hydration. Use of acetylsalicylic acid (e.g. aspirin) andnon steroidal anti-inflammatory drugs (e.g. Ibuprofen) is not recommended. Yet, we can have anotherlook over the signs and symptoms of dengue for a little more information: This infectious disease ismanifested by a sudden onset of fever, with severe headache, muscle and joint pains (myalgias andarthralgiassevere pain gives it the name break-bone fever or bonecrusher disease) and rashes. Thedengue rash is characteristically bright red petechiae and usually appears first on the lower limbs andthe chest; in some patients, it spreads to cover most of the body. There may also be gastritis with somecombination 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 asinfluenza or other viral infection. Thus travelers from tropical areas may inadvertently pass on dengue intheir home countries, having not been properly diagnosed at the height of their illness. Patients withdengue can pass on the infection only through mosquitoes or blood products and only while they arestill febrile. The classic dengue fever lasts about six to seven days, with a smaller peak of fever at thetrailing end of the disease (the so-called biphasic pattern ). Clinically, the platelet count will drop untilthe 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 shocksyndrome (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: TheWHO definition of dengue hemorrhagic fever has been in use since 1975; all four criteria must befulfilled: 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 permm³ 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 baselinefollowing IV fluid, pleural effusion, ascites, hypoproteinemia)In other words, dengue hemorrhagic fever (DHF) is a specific syndrome that tends to affect childrenunder 10. It causes abdominal pain, hemorrhage (bleeding), and circulatory collapse (shock). DHF is alsocalled Philippine, Thai, or Southeast Asian hemorrhagic fever and dengue shock syndrome.DHF starts abruptly with high continuous fever and headache. There are respiratory and intestinalsymptoms with sore throat, cough, nausea, vomiting, and abdominal pain. Shock occurs two to six daysafter 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 easybruising, 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 theheart (myocarditis) may be present.Patients with DHF must be monitored closely for the first few days since shock may occur or recurprecipitously. Cyanotic (bluish) patients are given oxygen. Vascular collapse (shock) requires immediatefluid 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.DiagnosisThe diagnosis of dengue is usually made clinically. The classic picture is high fever with no localisingsource of infection, a petechial rash with thrombocytopenia and relative leukopenia. Serology andpolymerase chain reaction (PCR) studies are available to confirm the diagnosis of dengue if clinicallyindicated.How is dengue fever treated?Because dengue is caused by a virus, there is no specific medicine or antibiotic to treat it. For typicaldengue, the treatment is purely concerned with relief of the symptoms (symptomatic). Rest and fluidintake for adequate hydration is important. Aspirin and nonsteroidal anti-inflammatory drugs should beavoided. Acetaminophen (Tylenol) and codeine may be given for severe headache and for the joint andmuscle pain (myalgia). The mainstay of treatment is supportive therapy. Increased oral fluid intake isrecommended 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 oralintake. A platelet transfusion is indicated in rare cases if the platelet level drops significantly (below20,000) or if there is significant bleeding. The presence of melena may indicate internal gastrointestinalbleeding 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 associatedwith some of these infections. Patients may receive paracetamol preparations to deal with thesesymptoms if dengue is suspected.Emerging treatments Emerging evidence suggests that mycophenolic acid and ribavirin inhibit denguereplication. Initial experiments showed a fivefold increase in defective viral RNA production by cellstreated 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, oneof the many ongoing vaccine development programs is the Pediatric Dengue Vaccine Initiative whichwas 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 adengue fever vaccine on 3,0005,000 human volunteers after having successfully conducted tests onanimals and a small group of human volunteers. And, a number of other vaccine candidates are enteringphase I or II testing. Mosquito control A field technician looking for larvae in standing water containersduring the 1965 Aedes aegypti eradication program in Miami, Florida. In the 1960s, a major effort wasmade to eradicate the principal urban vector mosquito of dengue and yellow fever viruses, Aedesaegypti, from southeast United States. Primary prevention of dengue mainly resides in mosquitocontrol. 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 periodicdraining of artificial containers is the most effective way of reducing the larva and thereby the aedesmosquito load in the community. Larvicide treatment is another effective way of control the vectorlarvae but the larvicide chosen should be long lasting and preferably have World Health Organizationclearance 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. In1998, scientists from the Queensland Institute of Research in Australia and Vietnam'sMinistry of Health introduced a scheme that encouraged children to place a water bug, the crustaceanMesocyclops, in water tanks and discarded containers where the Aedes aegypti mosquito was known tothrive. This method is viewed as being more cost-effective and more environmentally friendly thanpesticides, though not as effective, and requires the ongoing participation of the community. Personalprotection Personal prevention consists of the use of mosquito nets, repellents containing NNDB or
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