| Fact | Explanation |
|---|---|
| Exposure to mosquito bite | Dengue fever is caused by an RNA virus which has 4 serotypes named dengue virus type 1 to type 4. Infection with one serotype provides life-long immunity against that particular serotype, and partial immunity against other serotypes. When a person who is immune to one serotype gets infected with another serotype, the risk of developing severe dengue is high. After the incubation period, febrile phase starts which is followed by the critical phase and recovery phase. [6,7] However these sequence of events might not be present in all patients with dengue. Some patients may not enter the critical phase and some remain asymptomatic. [8] |
| Symptoms during the febrile period | Fever is preceded by the prodromal symptoms (chills, erythematous diffuse skin rash and facial flushing). [2] Infants and young children may present with mild fever but adults usually present with rapidly rising fever often more than 39°C. Nausea and or vomiting are common associations of fever. During the febrile period patients often complain of severe retro-orbital headache, arthralgia, myalgia and fatigue. [2] Petechiae, bruising and macular or maculopapular erythematous skin rash can develop during the febrile phase. [4,6] |
| Symptoms during the critical phase | During the critical phase plasma leaking and hemorrhagic manifestations occur and it happens around the time of defervescence (roughly 4-5 days after the onset of fever and lasts about 48 hours). [2,5,6] Cutaneous bleeding and mucosal bleeding (hemoptysis, melena, vaginal bleeding, and epistaxis) manifest during this phase. [2,3,6] Dengue shock syndrome can occur during this phase. [6] Severe dengue is a deadly consequence of dengue fever that can occur during the critical phase, and it is the cumulative effect of plasma leak, respiratory failure, severe hemorrhage, and multi organ failure. Patients often complain of severe abdominal pain, persistent vomiting, hematemesis, gum bleeding, rapid breathing, fatigue and restlessness. [7] |
| Symptoms during the recovery phase | Patients often complain of rapid improvement of the symptoms. Cutaneous manifestations include asymptomatic or itchy maculopapular rash. Fatigue may remain even after the recovery period in adults and may last about several weeks. [6] |
| Risk factors | A recent history of travel to an endemic area and presence of diagnosed patients with dengue fever in the near vicinity and living in an environment with lot of mosquito breeding sites are risk factors. [1] |
| Fact | Explanation |
|---|---|
| Febrile phase | As the name implies patients are febrile and can have mild hemorrhagic manifestations like, petechiae and skin bruising. [1,6] Hepatomegaly, the most valuable indicator of hepatic involvement in dengue fever is detected during the febrile phase and often associated with jaundice. [4,5] Lymphadenopathy occurs due to viral replication within the lymph nodes. [3] |
| Signs during the critical phase | Patients are usually afebrile. Plasma leaking reduces the circulatory volume and patients develop tachycardia, narrow pulse pressure hypotension, cold blotchy skin congested peripheries, and central cyanosis occurs with circulatory collapse. [4] Plasma leaking results in pleural effusions and ascites. [4] Petechiae, epistaxis, and gingival bleeding are cutaneous manifestations. [1,2] Tourniquet test usually becomes positive during the hemorrhagic phase. Although positive tourniquet test only suggests dengue fever a negative test cannot exclude the possibility of dengue. [7] Tender hepatomegaly is still present during the critical phase as well. [6] |
| Signs during the recovery phase | A maculopapular skin rash and desquamation of the skin lesions are seen during the recovery phase. [6] |
| Fact | Explanation |
|---|---|
| Viral fever [1] | Most children and infants present with non-specific symptoms and fever resembling more common viral fever. Chikungunya fever have rapid onset of symptoms and a shorter febrile period. [2,4] Koplik's spots which appear during the prodromal phase are pathognomonic of measles. [1] Rubella, Roseola infantum, infectious mononucleosis, typhoid fever, leptospirosis are other infective causes presenting with fever and rash. [1] Infection with enterovirus, adenovirus, malaria, viral hepatitis, rickettsial diseases, and bacterial sepsis should also be considered. [5] |
| Scarlet fever | Another differential diagnosis for fever with rash. Skin rash appears after 12 hours to 2days of onset of fever and become generalized within few hours. [1] |
| Kawasaki disease | Often high spiking fever is prolonged and should be suspected in patients with bilateral non-suppurative conjunctivitis, red cracked lips, “strawberry tongue”, peeling of the skin from fingertips and polymorphic macular, maculopapular or urticarial rash. [3] |
| Infective exanthems | Skin manifestations of dengue fever may mimic bacterial or viral exanthems. [1] |
| Fact | Explanation |
|---|---|
| Full blood count | Thrombocytopenia and leucopenia are seen in full blood count. In some patients platelet count can be normal. Packed cell volume is raised in dengue hemorrhagic fever. [1,3] |
| Reverse transcription (RT)-PCR | Detects the dengue antigen and enables the diagnosis within 2 to 7 days of illness. [2] |
| Enzyme-linked immunosorbent assay (ELISA) | ELISA can detect antibodies against dengue virus. Ig M type indicates an acute infection and Ig G type indicates a secondary infection. [5] ELISA is also useful in detecting E/M antigen and the NS1 antigen up to 9days from the onset of symptoms. [2,4] |
| Fact | Explanation |
|---|---|
| Liver function test | Hepatic transaminases are elevated and the liver function can be deranged. Acute liver failure can occur with multi organ dysfunction syndrome. [1,2] |
| Renal function test | Assessment of the renal function is important as acute renal failure is a complication of severe dengue. [3] |
| Fact | Explanation |
|---|---|
| Full blood count | Full blood count should be repeated at least once a day to detect the progression of the disease. Platelet count is considered as the surrogate marker to monitor the disease progress. Platelet count drops rapidly during the febrile phase and the lowest value is recorded during the critical phase. Platelet count less than 100,000/μL indicates impending dengue hemorrhagic fever or dengue shock syndrome. [9] Hemoconcentration occurs in the critical phase due to plasma leaking. So the packed cell volume rises. 20% or more rise in packed cell volume from the baseline value is diagnostic of dengue hemorrhagic fever. [2] With those clues in full blood count, evidence of fluid leakage (pleural effusion, pericardial effusion, ascites) should be looked for. Rising platelet counts indicates end of the critical phase and entering in to the recovery phase. |
| Ultrasound scan | Enables detection of hepatomegaly, pleural effusions, pericardial effusions and ascites in dengue hemorrhagic fever. [5] |
| Chest X-ray | Detect pleural effusions. But this is inferior to ultrasound scan in detecting pleural effusions. [6,7] Often lateral decubitus chest X-ray can detect small pleural effusions than an erect chest X-ray film. [9] |
| Serum electrolytes | Acute renal failure is a known complication of dengue hemorrhagic fever and dengue shock syndrome, but this is uncommon. [1] |
| Coagulation studies | Disseminated intravascular coagulation is a complication associated with dengue shock syndrome (DSS). [2] Prothrombin time prolongs in the presence of hepatic involvement. [3] |
| Hepatic transaminases | Elevated in hepatic involvement. [2,3] |
| Serum bilirubin | Can be increased due to hepatic involvement. [3] |
| Serum albumin | Low in dengue shock syndrome. [3] |
| Fibrin degradation products | Elevated in disseminated intra-vascular coagulation. [4] |
| Blood grouping and cross matching | Platelet transfusion may be needed in severe thrombocytopenia. [8] |
| Fact | Explanation |
|---|---|
| Health education | Preventive measures of dengue include destroying mosquito breeding sites and use of mosquito repellents and nets to avoid bitten by the mosquitoes. [1,2,3] Patients with dengue should be advised to take adequate rest and fluid intake. Patients should be warned not to take non-steroidal anti-inflammatory drugs for fever especially during outbreaks. [3] Patients can be managed as an out patient during the febrile period and they should be advised to seek immediate health care if they develop dehydration, any bleeding manifestations or if there is no symptom improvement with the settlement of fever. [4] |
| Fluid management | Fluid management is the mainstay of treatment. Patients who are in the febrile phase can be managed with oral hydration. But regular monitoring is necessary for the early detection of entering in to the critical phase. [4] Once the critical period is over patient can be asked to take oral fluid with no restriction. [5] |
| Antipyeritics | Paracitamol is the drug of choice and non-steroidal anti-inflammatory drugs are contraindicated. [3] |
| Fact | Explanation |
|---|---|
| Fluid management during the critical period (in the absence of shock) | Patients usually need intravenous fluids during the critical phase. The total fluid requirement (both oral and intravenous) for the 48 hours of critical period is, the sum of maintenance fluid requirement for 24 hours and the fluid deficit, 50 mL/kg calculated up to 50kg of maximum body weight. This amount is to be spread over the critical period, as excessive and injudicious fluid administration can lead to fluid overload and pulmonary edema. Signs of fluid overload (puffy eyes, pulmonary edema) should be cautiously looked for during this period. Sometimes in severe dengue patients need blood transfusions to maintain the intravascular volume. If the hematocrit continue to fall despite adequate fluid replacement, either internal bleeding or end of the critical period should be suspected (As the recovery phase begins extravasated fluid is reabsorbed in to the intravascular compartment, so the hematocrit drops). Cross-matched whole blood should be transfused if significant bleeding (more than 300 ml) develops. Transfusion of platelets is indicated if platelet counts are very low. [1,2] |
| Fluid management in dengue shock | In the presence of dengue shock fluid boluses (20 mL/kg) should be administered until the blood pressure is recordable. Crystalloids are preferred for the initial fluid resuscitation and colloids (dextran) should be used as the second line choice if the blood pressure is not responding to crystalloids. [1,2,3] After patient recovers from the shock the rest of the calculated fluid volume should be administrated not exceeding that. |