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Monday, September 19, 2011

Your Guide to Dengue Fever


Dengue Fever is a major global health threat and a leading cause of mortality in the tropics and subtropics. It is caused by infection with any one of four serotypes of dengue virus transmitted by the bite of the Aedes mosquito. This mosquito species breeds around habitations and feeds during the day. As many as 100 million people are infected annually, of which about 25,000 die of the disease.

<<< The Aedes mosquito and its infamous black and white stripes.



Presentation
Once inoculated into the human body, dengue has an incubation period (during which the virus multiplies) of 3-14 days. Thereafter, in the typical form of the disease, a five- to seven-day acute fever ensues. Recovery is usually complete by 7-10 days.
It is important to appreciate that about half of all dengue infections go completely unnoticed. Some patients have isolated fever while others may produce the typical symptom complex of classic dengue fever (DF). Fever may be as high as 106°F. The fever presents in a nonspecific manner and may not be distinguishable from other infectious illnesses. The fever in DF is often preceded by chills, red speckles on the skin, and facial flushing. It typically begins on the third day of symptoms and lasts five to seven days. The other symptoms associated with DF include headache, which is usually generalised, pain in the back of the eye, nausea or vomiting and a rash that begins on day three and persists for about three days. DF can also be associated with muscle aches, joint pains and generalised fatigue. Abdominal pain when present can be a heralding sign of a more serious form of the disease, known as dengue hemorrhagic fever (DHF).


DHF is characterised by bleeding. This may be as mild as small amounts of oozing from the nose or gums or serious enough to present with copious bloody vomiting, an abnormally heavy period or excessive blood in the stool. Abdominal pain, excessive restlessness, confusion, decrease in body temperature, and a drop in the platelet count are indicators of imminent DHF.

Patients who have previously had DF (over half of which go unnoticed) are specifically at risk for development of DHF. It is also important to keep in mind that it is at the time when the fever is receding that DF patients are at greatest risk for DHF. This is the time to watch for the warning signs mentioned above and seek emergency care. If not properly taken care of, DHF complications (particularly gastrointestinal bleeding) can worsen and induce shock. This most severe and fatal form of dengue is known as Dengue Shock Syndrome (DSS). DSS is characterised by cold-clammy skin, a fast heart rate, decreased blood pressure, delirium, difficulty breathing and damage to the internal organs specifically the liver and kidney. DSS can lead to multiorgan failure and death.

Outcome

Most patients achieve a complete recovery from dengue. Even patients with DHF and DSS usually recover with proper resuscitation. Infection with one dengue serotype confers lifelong immunity against that particular serotype, but still leaves the individual susceptible to the other three serotypes. As mentioned above, a subsequent infection by a different serotype is a major risk factor for the development of DHF and, as a result, DSS.

Prevention

No vaccine is currently available to prevent contracting the dengue virus. Consequently, the most effective protective measures are those that avoid mosquito bites. Repellants and protective clothing are simple effective measures to take. Even better, eliminate mosquito breeding grounds: ensure no water is left standing in flower vases, old tires, etc. Since the Aedes is a day-biting mosquito, mosquito nets are not useful.

Diagnosis

DF is diagnosed clinically, based on the patient’s presenting symptoms and signs. A complete blood count might reveal a low white cell and platelet count. Serological testing and PCR are not only very costly but are unhelpful in the initial stages of the disease.

Treatment
Dengue fever is usually a self-limited illness, and only supportive care is required. No specific antiviral medication currently is available to treat dengue infections. Paracetamol should be used to manage the fever. Other agents including aspirin should be avoided, especially in children.

Patients may become dehydrated from fever, vomiting or lack of adequate dietary intake. Patients who are able to tolerate oral fluids should be encouraged to drink oral rehydration solution, fruit juice or water to prevent dehydration. Patients who improve can continue to be monitored in an outpatient setting. Patients who do not improve should be admitted to the hospital for hydration. Patients with dengue shock syndrome are treated in intensive/critical care units.

No specific diet is necessary for patients with dengue fever. Bed rest is advised.

Patients with known or suspected dengue fever should have their blood counts measured daily from the third day of illness until one to two days after the fever abates. Patients whose condition improves can continue to be monitored in an outpatient setting. Patients who do not improve should be admitted to the hospital for hydration.

When the patient’s fever is going away, watch for the warning signs mentioned above (taken from the CDC site here). If any of them appear, take the patient to the Emergency department of your nearest hospital immediately.

By Kashif N Chaudhry: http://www.newslinemagazine.com/2011/09/your-guide-to-dengue-fever/

Platelets, or thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are small, irregularly shaped clear cell fragments (i.e. cells that do not have a nucleus containing DNA), 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes.  The average lifespan of a platelet is normally just 5 to 9 days. Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots. [Dengue fever reduces platelets level ]
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Less than 50,000 platelets count worrisome, says doctor

Humidity, Aedes-mosquito, fresh stagnant water and plus the virus compiles and forms Dengue Fever. The platelets count is the only option physicians deal with in the initial stages. Platelets count should not drop in the patients suffering from dengue, said Dr. Abdus Salam, Director Emergency Room of Shifa International Hospital while addressing an awareness session in Hospital. Less than 50,000 platelets count with bleeding is a worrisome situation for the doctors, as alarmed Dr Salam. If the patient’s platelets count is 10,000 with no bleeding; internal or external the patient is in out of the danger zone. The normal platelet count is 150,000 up to 450,000. Salam informed this scribe that the symptoms include fever, headache, muscle and joint pains and a characteristic skin rash that is similar to measles. In a small proportion of cases the disease develops into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs. Dr. Salam informed that only eight hours are required for the mosquito to breed from the development from an egg to larvae. He alarmed the audience to double check for rainwater stored at places as the monsoon continues.
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If the number of platelets is too low, excessive bleeding can occur. However, if the number of platelets is too high, blood clots can form (thrombosis), which may obstruct blood vessels and result in such events as a stroke, myocardial infarction, pulmonary embolism or the blockage of blood vessels to other parts of the body, such as the extremities of the arms or legs.  An abnormality or disease of the platelets is called a thrombocytopathy, which could be either a low number of platelets (thrombocytopenia), a decrease in function of platelets (thrombasthenia), or an increase in the number of platelets (thrombocytosis). There are disorders that reduce the number of platelets, such as heparin-induced thrombocytopenia (HIT) or thrombotic thrombocytopenic purpura (TTP) that typically cause thromboses, or clots, instead of bleeding.

Platelets release a multitude of growth factors including Platelet-derived growth factor (PDGF), a potent chemotactic agent, and TGF beta, which stimulates the deposition of extracellular matrix.  Both of these growth factors have been shown to play a significant role in the repair and regeneration of connective tissues.  Other healing-associated growth factors produced by platelets include basic fibroblast growth factor, insulin-like growth factor 1, platelet-derived epidermal growth factor, and vascular endothelial growth factor.  Local application of these factors in increased concentrations through Platelet-rich plasma (PRP) has been used as an adjunct to wound healing for several decades.
High and low counts
A normal platelet count in a healthy individual is between 150,000 and 450,000 per μl (microlitre) of blood ((150–450)×109/L). Ninety-five percent of healthy people will have platelet counts in this range.  Some will have statistically abnormal platelet counts while having no demonstrable abnormality. However, if it is either very low or very high, the likelihood of an abnormality being present is higher.

Both thrombocytopenia and thrombocytosis may present with coagulation problems.  In general, low platelet counts increase bleeding risks; however there are exceptions (such as immune-mediated heparin-induced thrombocytopenia or paroxysmal nocturnal hemoglobinuria). High counts may lead to thrombosis, although this is mainly when the elevated count is due to myeloproliferative disorder.

Transfusion is generally used only to correct unusually low platelet counts (typically below (1.0–1.5)×1010/L). Transfusion is contraindicated in thrombotic thrombocytopenic purpura (TTP), as it fuels the coagulopathy. In patients undergoing surgery, a level below 5×1010/L is associated with abnormal surgical bleeding, and regional anaesthetic procedures such as epidurals are avoided for levels below 80–100.

Normal platelet counts are not a guarantee of adequate function.  In some states, the platelets, while being adequate in number, are dysfunctional.  For instance, aspirin irreversibly disrupts platelet function by inhibiting cyclooxygenase-1 (COX1), and hence normal hemostasis.  The resulting platelets are unable to produce new cyclooxygenase because they have no DNA.  Normal platelet function will not return until the use of aspirin has ceased and enough of the affected platelets have been replaced by new ones, which can take over a week.  Ibuprofen, another NSAID, does not have such a long duration effect, with platelet function usually returning within 24 hours,and taking ibuprofen before aspirin will prevent the irreversible effects of aspirin.[18]  Uremia, a consequence of renal failure, leads to platelet dysfunction that may be ameliorated by the administration of desmopressin.

Medications
Oral agents often used to alter/suppress platelet function include aspirin, clopidogrel, cilostazol, ticlopidine, and prasugrel.
Intravenous agents often used to alter/suppress platelet function include: abciximab, eptifibatide, tirofiban.
In addition to platelet transfusion, hematopoetic agents such as Oprelvekin, Romiplostim, and Eltrombopag can be used to increase platelet counts.

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