Dengue fever also known as breakbone fever is a mosquito-borne infectious tropical disease caused by the dengue virus. 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 life-threatening dengue hemorrhagic fever, which results in bleeding, thrombocytopenia, and leakage of blood plasma, or into dengue shock syndrome, in which dangerously low blood pressure occurs. Treatment of acute dengue fever is supportive, with either oral or intravenous rehydration for mild or moderate disease and use of intravenous fluids and blood transfusion for more severe cases. Along with attempts to eliminate the mosquito vector, work is ongoing to develop a vaccine and medications targeted directly at the virus.
Dengue is an acute febrile illness characterized by severe muscle and joint pain, rash, malaise, and lymphadenopathy. The severity of the musculoskeletal complaints gave rise to the sobriquet breakbone fever.
Dengue virus (DENV) belongs to the family Flaviviridae, genus Flavivirus, and is transmitted to humans by Aedes mosquitoes, mainly Aedes aegypti. Based on neutralization assay data, four serotypes (DENV-1, DENV-2, DENV-3, and DENV-4) can be distinguished. DENV infection is a major cause of disease in tropical and subtropical areas, with an estimated 50 million infections occurring each year and more than 2.5 billion people being at risk of infection [rx].
Types of Dengue Fever
The WHO classifies DF into two groups
According to the 1997 classification, dengue can be divided into an undifferentiated fever, DF, and DHF.[rx] DHF was further subdivided into grades I–IV.
- Grade I: Only mild bruising or a positive tourniquet test
- Grade II: Spontaneous bleeding into the skin and elsewhere
- Grade III: Clinical sign of shock
- Grade IV: Severe shock – feeble pulse, and blood pressure cannot be recorded.[rx]
Here, grades III and IV comprise DSS.[rx]
According to the severity of fever
Mild Dengue Fever
Symptoms can appear up to 7 days after being bitten by the mosquito that carries the virus.
- Aching muscles and joints
- Body rash that can disappear and then reappear
- High fever
- Intense headache
- Pain behind the eyes
- Vomiting and feeling nauseous
Symptoms usually disappear after a week, and mild dengue rarely involves serious or fatal complications.
Dengue Hemorrhagic Fever
At first, symptoms of DHF may be mild, but they gradually worsen within a few days. As well as mild dengue symptoms, there may be signs of internal bleeding. DHF is frequently seen during secondary dengue infection. However, in infants, it may also occur during a primary infection due to maternally attained dengue antibodies.[rx] The proposed diagnostic criteria for DHF include:[rx]
- Clinical parameters Acute-onset febrile phase – high-grade fever lasting from 2 days to 1 week. Hemorrhagic episodes (at least one of the following forms): Petechiae, purpura, ecchymosis, epistaxis, gingival and mucosal bleeding, GIT or injection site, hematemesis and/or Malena
Positive tourniquet and hepatomegaly.
- Laboratory parameters – Thrombocytopenia (platelet count <100,000/cu mm)
A person with Dengue hemorrhagic fever may experience
- Bleeding from the mouth, gums, or nose
- Clammy skin
- Damage to lymph and blood vessels
- Internal bleeding, which can lead to black vomit and feces, or stools
- A lower number of platelets in the blood
- Sensitive stomach
- Small blood spots under the skin
- Weak pulse
Without prompt treatment, DHF can be fatal.
Dengue Shock Syndrome
DSS is a severe form of dengue. It can be fatal.
Apart from symptoms of mild dengue fever, the person may experience:
- Intense stomach pain
- Sudden hypotension, or a fast drop in blood pressure
- Heavy bleeding
- Regular vomiting
- Blood vessels leaking fluid
Without treatment, this can result in death.
Criteria for Dengue Include
Probable dengue – The patient lives in or has traveled to a dengue-endemic area. Symptoms include fever and two of the following: nausea, vomiting, rash, myalgias, arthralgias, rash, positive tourniquet test, or leukopenia.
Warning Signs of Dengue – Abdominal pain, persistent vomiting, clinical fluid accumulation such as ascites or pleural effusion, mucosal bleeding, lethargy, liver enlargement greater than 2 cm, increase in hematocrit, and thrombocytopenia.
Severe Dengue – Dengue fever with severe plasma leakage, hemorrhage, organ dysfunction including transaminitis greater than 1000 international units per liter, impaired consciousness, myocardial dysfunction, and pulmonary dysfunction.
Dengue shock syndrome clinical warnings – Symptoms include rapidly rising hematocrit, intense abdominal pain, persistent vomiting, and narrowed or absent blood pressure.
The virus antigen can be detected by ELISA, polymerase chain reaction, or isolation of the virus from body fluids. Serology will reveal a marked increase in immunoglobulins. It is vital to assess pregnant patients with dengue as the symptoms may be very similar to preeclampsia.
Mechanism of Dengue Fever
When a mosquito carrying dengue virus bites a person, the virus enters the skin together with the mosquito’s saliva. It binds to and enters white blood cells, and reproduces inside the cells while they move throughout the body. The white blood cells respond by producing a number of signaling proteins, such as cytokines and interferons, which are responsible for many of the symptoms, such as the fever, the flu-like symptoms, and the severe pains. In severe infection, the virus production inside the body is greatly increased, and many more organs (such as the liver and the bone marrow) can be affected. Fluid from the bloodstream leaks through the wall of small blood vessels into body cavities due to capillary permeability. As a result, less blood circulates in the blood vessels, and the blood pressure becomes so low that it cannot supply sufficient blood to vital organs. Furthermore, dysfunction of the bone marrow due to infection of the stromal cells leads to reduced numbers of platelets, which are necessary for effective blood clotting; this increases the risk of bleeding, the other major complication of dengue fever.[rx]
The Aedes aegypti mosquito is the primary vector of dengue. The virus is transmitted to humans through the bites of infected female mosquitoes. After virus incubation for 4–10 days, an infected mosquito is capable of transmitting the virus for the rest of its life.
Infected symptomatic or asymptomatic humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. Patients who are already infected with the dengue virus can transmit the infection (for 4–5 days; maximum 12) via Aedes mosquitoes after their first symptoms appear.
The Aedes aegypti mosquito lives in urban habitats and breeds mostly in man-made containers. Unlike other mosquitoes Ae. aegypti is a day-time feeder; its peak biting periods are early in the morning and in the evening before dusk. Female Ae. aegypti bites multiple people during each feeding period. Aedes eggs can remain dry for over a year in their breeding habitat and hatch when in contact with water.
Aedes albopictus, a secondary dengue vector in Asia, has spread to North America and more than 25 countries in the European Region, largely due to the international trade in used tires (a breeding habitat) and other goods (e.g. lucky bamboo). Ae. albopictus is highly adaptive and, therefore, can survive in cooler temperate regions of Europe. Its spread is due to its tolerance to temperatures below freezing, hibernation, and ability to shelter in microhabitats.[rx]
Through Mosquito Bites
Dengue viruses are spread to people through the bites of infected Aedes species mosquitoes (Ae. aegypti or Ae. albopictus). These are the same types of mosquitoes that spread Zika and chikungunya viruses.
- These mosquitoes typically lay eggs near standing water in containers that hold water, like buckets, bowls, animal dishes, flower pots, and vases.
- These mosquitoes prefer to bite people and live both indoors and outdoors near people.
- Mosquitoes that spread dengue, chikungunya, and Zika bite during the day and night.
- Mosquitoes become infected when they bite a person infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.
From mother to child
- A pregnant woman already infected with dengue can pass the virus to her fetus during pregnancy or around the time of birth.
- To date, there has been one documented report of dengue spread through breast milk. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas with risk of dengue.
Causes of Dengue Fever
|Soluble factor||Biological function in relation to pathogenesis|
|Thrombin||Thrombin is thought to act near the site at which it is produced. Thrombin converts circulating fibrinogen to fibrin and triggers platelet activation, which results in platelet aggregation. Thrombin activates EC and increases EC permeability, leading to plasma leakage and edema formation. Thrombin is chemotactic for monocytes and is mitogenic for lymphocytes and mesenchymal cells. Activated platelets release several soluble factors with inflammatory, antimicrobial, and immune modulating activity, such as MMP-9, which enhances EC permeability. Activated platelets also secrete soluble CD40 ligand, which can induce EC to produce reactive oxygen species, adhesion molecules, chemokines, and TF. Thrombin also inhibits IL-12 production by mononuclear cells.|
|C3a and C5a||C3a activates platelets and enhances their activation and adhesion properties. C5a enhances blood thrombogenicity by upregulating TF and PAI-1 expression on various cell types. C5a stimulates monocytes to produce IL-1, IL-6, IL-8, and TNF-α. Activation of these complement factors is enhanced by thrombin, which cleaves C3 and C5 to C3a/b and C5a/b, respectively. Activated platelets are also involved in C3 cleavage, which induces activation of the classical complement pathway.|
|C4b||C4b binds to protein S and thereby inhibit the anticoagulant properties of activated protein C-protein S complexes.|
|IL-1||IL-1β is a major mediator of platelet-induced activation of EC, causing enhanced chemokine release and upregulation of VCAM-1. VCAM-1 promotes adhesion of monocytes to the endothelium. IL-1 increases the expression of TF on EC and suppresses the cell surface anticoagulant activity of EC. Depending on its concentration, it may upregulate TNF-α production or downregulate TNF-receptors. IL-1 stimulates the hypothalamus and, as a consequence, the pituitary gland to produce anti-inflammatory mediators such as endorphins, melanocyte-stimulating hormone, and adrenocorticotropic hormone.|
|IL-6||Together with other proinflammatory cytokines, IL-6 potentiates the coagulation cascade. It can downregulate the production of TNF-α and TNF receptors. IL-6, together with IL-1, is a potent inducer of fever.|
|IL-8||IL-8 is a chemokine that is abundantly produced by monocytes, EC, and hepatocytes. EC damage in the liver may elevate systemic concentrations. Activation of the coagulation system results in increased expression of IL-6 and IL-8 by monocytes, while the APC-PS anticoagulation pathway downregulates production of IL-8 by EC.|
|IL-10||IL-10 is produced by monocytes and regulatory T helper cells and may cause platelet decay. Thrombin can stimulate IL-10 production by monocytes. The cytokine downregulates the inflammatory response and creates a proviral survival milieu. IL-10 promotes OAS by inhibiting the development of effector T cells to new epitopes. IL-10 also inhibits the expression of TF and inhibits fibrinolysis.|
|TNF-α||TNF-α in a potent activator of EC and enhances capillary permeability. TNF-α upregulates expression of TF on monocytes and EC and downregulates the expression of thrombomodulin on EC. It also activates the fibrinolysis system. TNF-α enhances expression of NO and mediates activation-induced death of T cells, and it has therefore been implicated in peripheral T-cell deletion.|
|TGF-β||TGF-β may act as a proinflammatory or anti-inflammatory cytokine, depending on its concentration. Early in infection, low levels of TGF-β may trigger the secretion of IL-1 and TNF-α. However, later in infection, the cytokine inhibits the Th1 response and enhances the production of Th2 cytokines such as IL-10. TGF-β increases expression of TF on EC and upregulates expression and release of PAI-1.|
|NO||NO has a multifaceted role in inflammatory reactions. It enhances the vasodilatation and formation of edema. It upregulates TNF-α production in monocytes. At low concentrations, it protects cells from apoptosis, while at high concentrations it induces apoptosis. NO downregulates expression of MHC class II and suppresses the expansion of Th1 cells. Maintenance of the EC barrier requires a basal level of NO. Both a lack of NO and high NO levels destabilize EC junctions.|
|VEGF||VEGF is a key driver of vascular permeability. It reduces EC occludins, claudins, and VE-cadherin content, all of which are components of EC junctions. Upon activation, VEGF stimulates expression of ICAM-1, VCAM-1, and E-selectin in EC.|
Symptoms of Dengue Fever
|Characteristics||Malaria infection||Dengue infection||Concurrent infection|
|Mode of transmission||Mosquito-borne (Anopheles)||Mosquito-borne (Aedes)||Mosquito-borne (Anopheles + Aedes)|
|Fever||Acute febrile illness (chronic in some cases)||Acute febrile illness||Acute febrile illness|
|Atypical lymphocytosis||Usually negative||Usually positive||Usually positive|
|Hemoconcentration||Usually negative||Usually positive||Usually positive|
|Thrombocytopenia||Usually negative||Usually positive||Usually positive|
|Tourniquet test||Usually negative||Usually positive||Usually positive|
|Treatment||Antimalarial drug||Fluid therapy||Antimalarial drug with fluid therapy|
According to the WHO 2011 case definition [rx], dengue infection is suspected in a patient with high fever and two of the following signs or symptoms:
- Sudden, high fever
- Severe headaches
- Pain behind the eyes
- Severe joint and muscle pain
- Retro-orbital pain
- Arthralgia/ bone pain
- Bleeding manifestations – petechiae, epistaxis, gum bleeding, hematemesis, melena, or positive tourniquet test.
- Stomach or belly pain, tenderness
- Vomiting (at least 3 times in 24 hours)
- Bleeding from the nose or gums
- Vomiting blood, or blood in the stool
- Feeling tired, restless, or irritable
- Serosal effusion
- Lethargy or restlessness
- High hematocrit combined with low platelet count
- Mucosal bleeding
- Enlargement of the liver
- Ongoing vomiting
- Worsening abdominal pain [rx,rx]
- Leukopenia (WBC ≤ 5,000 cells/mm3)
- Platelet count ≤ 150,000 cell/mm3
- Hematocrit (Hct) rising 5–10%.
- Skin rash, which appears two to five days after the onset of fever
- Mild bleeding (such a nose bleed, bleeding gums, or easy bruising)
- UF cannot be diagnosed clinically and the diagnosis is based on serology or virology.
- DF is considered to be a mild disease because death is rarely reported, but massive bleeding may be associated with DF.
- DHF – clinical presentations during the febrile phase are similar to those in DF. The distinct feature of DHF is the increase in vascular permeability (plasma leakage) that differentiates DHF from DF. The plasma leakage is selective leakage into the pleural and peritoneal cavities that results in pleural effusion and ascites.
- DSS – presentations are the same as those in DHF but the plasma leakage is so severe that the patient develops shock.
- UD – most of the unusual cases are DHF cases with prolonged shock or DHF inpatients with co-morbidities or DHF together with other infections [rx].
|An acute febrile illness with ≥2 of the following manifestations:||All of the following must be present:||All 4 criteria for DHF must be met, plus evidence of circulatory failure manifested by:|
|Fever or history of acute fever, lasting 2-7 d|
|Headache||Bleeding, evidenced by at least one of the following:||Rapid and weak pulse,|
|Myalgia||Positive tourniquet test result†||Narrow pulse pressure|
|Arthralgia||Petechiae, ecchymoses, or purpura||or|
|Rash||Bleeding from the mucosa, GI tract, injection sites, or other locations||Hypotension for age (systolic pressure < 80 mm Hg for those < age 5 y, or <90 mm Hg for those > age 5 y)|
|Leukopenia||Hematemesis or melena|
|AND||Thrombocytopenia (≤ 100,000 cells/mm3)||Cold clammy skin and restlessness|
|OR||Evidence of plasma leakage caused by increased vascular permeability, manifested by at least one of the following:|
|The occurrence at the same location and time as other confirmed cases of DF|
|Laboratory criteria||Increase in hematocrit ≥ 20% above average for age, sex, and population|
|Isolation of dengue virus ≥ 4-Fold change in antibody titers|
|The decrease in hematocrit after volume-replacement treatment ≥ 20% of baseline|
|Demonstration of dengue virus antigen|
|Detection of dengue virus genomic sequence||Signs of plasma leakage such as pleural effusion, ascites, and hypoproteinemia|
Adapted from the World Health Organization.[rx]
DF, Dengue fever; DHF, dengue hemorrhagic fever; DSS, dengue shock syndrome; GI, gastrointestinal.
- Grade I: fever and nonspecific constitutional symptoms; only hemorrhagic manifestation is a positive tourniquet test and/or easy bruising.
- Grade II: same as grade I but includes spontaneous bleeding.
- Grade III: Circulatory failure manifested by a rapid, weak pulse and narrowing of the pulse pressure or hypotension.
- Grade IV: Profound shock with undetectable blood pressure or pulse. Grades III and IV define DSS.
Diagnosis of Dengue Fever
Confirmed dengue infection
IgM or IgG seroconversion
Probable dengue infection
Elevated IgG titer (that is, 1,280 or greater by haemagglutination inhibition test)
|Disease||Presenting symptoms||Exanthem||Timing from symptoms to rash||Distinguishing features|
|Chikungunya fever||Fever, arthralgia, myalgia, HA, ± vomiting, diarrhea||Flushing erythema on the face and upper aspect of the chest.[rx]||24 h||Asia, Africa, Indian Ocean|
|Sandfly fever||Fever, HA, malaise, retro-orbital pain||Flushing scarlatiniform erythema on face and neck. Very rare reports of subsequent rash (urticaria, erythema-multiforme, morbilliform). Lack of later rash helps distinguish from dengue fever.[rx]||Concomitant||Mediterranean, Asia, Africa|
|Scarlet fever||Fever, pharyngitis, ± vomiting, abdominal pain, ± convulsions||Initially on neck/chest. The rapid development of 1- to 2-mm papules on the erythematous background (sandpaper). Linear petechiae (Pastia’s lines) in the skin folds. Subsequent membranous desquamation of palms/soles. White, then red, strawberry tongue.[rx]||12-48 h||ASO titer positive, leukocytosis|
|Toxic shock syndrome||Fever, hypotension||Generalized erythroderma or scarlatiniform rash. Erythema/edema of palms/soles. Strawberry tongue, conjunctival injection. Desquamation of palms/soles 1-2 wk after disease onset.[rx]||Concomitant||Staphylococcal or streptococcal infection|
|Kawasaki disease||Fever, LAD, oropharyngeal change, conjunctival injection||Polymorphic, including flushing macular erythema, nonpruritic erythematous plaques, erythema marginatum, pustules. Perineal involvement. Strawberry tongue, conjunctival hyperemia. Edema, erythema, then desquamation of palms/soles.[rx]||Concomitant||± Cardiac abnormalities|
|Erythema infectiosum (parvovirus B19)||Fever, HA, rhinorrhea||Initial macular fiery erythema of cheeks with circumoral pallor. In 1-4 d, morbilliform reticulated eruption on extremities (spares palms/soles); recurring stage (rash on exposure to trigger).[rx]||1-2 d||Arthritis in 80% of adults|
ASO, Antistreptolysin O; HA, headache; LAD, lymphadenopathy.
Test / Differential diagnosis
|Disease||Presenting symptoms||Exanthem||Timing from symptoms to rash||Distinguishing features|
|Infectious mononucleosis (EBV, CMV)||Fever, malaise, pharyngitis, LAD||Polymorphic, including generalized macular erythema ± petechiae, urticaria, scarlatiniform, erythema multiforme-like. The rash is rare (3%-10%).[rx,rx] Eyelid edema. Pinhead petechiae at the junction of the soft/hard palate (Forschheimer’s spots).||Within first week of illness|
|Roseola infantum (HHV 6)||Fever, LAD ± convulsions||Mostly discrete pink macules, occasional papules. Often starts on the back. The fully developed rash usually involves the trunk, nape of the neck, proximal limbs ± scalp. Rare for face involvement. Total duration 24-72 h. Nonpruritic. Not followed by desquamation or pigment change.[rx]||As fever subsides||Age 6-36 mo; reactivation in immunocompromised hosts; associated with DRESS syndrome (controversial)rx]|
|Measles||Fever, cough, coryza||Initial erythematous papules on the face; within 1-2 d, spreads to the trunk. Small bright red spots with blue-white center on buccal mucosa–often appear at the beginning stage of exanthem (Koplick spots).[rx]||1-7 d|
|Rubella||Fever, eye pain, LAD||Initial “brilliant” generalized erythema on face, which fades within 24 h. Then, pale rose-pink macules appear on face and scalp that spread down trunk and extremities. Macules coalesce on the lower aspect of back/buttocks. Forschheimer’s spots.[rx]||2-5 d|
|Enterovirus||Fever ± pharyngitis||Polymorphic, including diffuse macular or morbilliform eruption. ±Vesicles, petechiae, purpura.[rx]||Varies||Associated with myocarditis|
|Secondary syphilis||Fever, HA, pharyngitis, myalgia, weight loss, LAD||Polymorphic: macules/papules/psoriasiform papules. Often diffuse discrete red to red-brown papules involving palms and soles. ±Condyloma lata. ±Moth-eaten alopecia.[rx]||Weeks to months after the initial chance||Serology for RPR or VDRL|
|Typhoid fever||Fever, vomiting, diarrhea, HA||Rose spots: 2- to 4-mm pink grouped papules on the trunk or generalized erythema “erythema typos.”[rx]||2-4 wk||Rose spot cultures may be Salmonella typhi+|
|Chikungunya fever||Fever, arthralgia, myalgia, HA, LAD, vomiting, diarrhea||Erythematous macules and papules on the trunk and extremities with islands of sparing. ±Petechiae. Face spared. Burning sensation in pinna.[rx]||3-5 d||Asia, Africa, Indian Ocean|
|West Nile virus||Fever, seizures, ascending flaccid paralysis||Ill-defined erythematous-to-pink macules on the trunk, and proximal extremities with pruritus and dysesthesia. Spares face palms, soles, mucous membranes. Resolve without scaling.[rxx]||3-7 d||Asia, Africa, Europe, the United States[rx]|
|O’nyong-nyong fever||Fever, arthritis, LAD||Pruritic morbilliform eruption. Initially discrete, then confluent. Starts on the face spread to trunk and extremities. Favors neck, chest, back, flanks, inner aspect of thighs and arms. Does not desquamate.[rx]||4 d, but varies||Sub-Saharan Africa|
|Mayaro virus||Fever, HA, myalgia, arthralgia||Erythematous macules and papules with some areas of confluence. Extremities and trunk[rx] ± hand involvement. Relative sparing of the face. Rash more common in children (89%) than adults (53%).[rx]||As fever subsides||South America|
|Sindbis virus||Fever, fatigue, arthralgia/arthritis||Generalized morbilliform eruption. Reports of vesicles on pressure points (palms/soles).[rx]||3-4 d||Europe, Africa, Asia, Australia|
|Ross River disease||Fever, fatigue, arthralgia/arthritis||Most commonly maculopapular on trunk and limbs. ± Palm/sole/face/scalp involvement. Reports of vesicular or purpuric. The rash seen in about 50% of affected persons.[rx]||3-4 d||Australia, Papua New Guinea, Fiji, Samoa|
|Leptospirosis||Acute phase: fever, HA, myalgia, pharyngitis.
Immune phase: organ failure
|Acute phase: generalized morbilliform rash, most prominent on the trunk.[rx]
Immune phase: hemorrhage, bleeding, jaundice.
Jaundice with history of water exposure differentiates from dengue fever.[rx]
|Concomitant||History of exposure to fresh water|
|Acute retroviral syndrome (HIV)||Fever, fatigue, HA, pharyngitis, myalgias, LAD||Macules and papules on the trunk and upper arms.[rx] ±Palms and soles.||Concomitant|
CMV, Cytomegalovirus; DRESS, drug reaction with eosinophilia and systemic symptoms; EBV, Epstein-Barr virus; HA, headache; HHV, human herpesvirus; LAD, lymphadenopathy; RPR, rapid plasma reagin; VDRL, Venereal Disease Research Laboratory test.
- Although all four dengue serotypes were initially isolated from human serum by using baby mice (rx, rx, rx), this method is very time-consuming, slow, and expensive. Moreover, because of the low sensitivity of the method, many wild-type viruses cannot be isolated with baby mice.
- Those that are isolated frequently require numerous passages to adapt the viruses to growth in mice. This method is no longer recommended for the isolation of dengue viruses, but some laboratories continue to use it (rx). One advantage of using baby mice, however, is that other arboviruses that cause dengue-like illness may be isolated with this system.
Mammalian Cell Culture
- Mammalian cell cultures have many of the same disadvantages as baby mice for isolation of dengue viruses—they are expensive, slow, and insensitive (rx, rx, rx, rx).
- As with isolation systems that use baby mice, viruses that are isolated frequently require many passages before a consistent cytopathic effect can be observed in the infected cultures. Although the use of this method continues in some laboratories, it is not recommended (rx, rx).
- Mosquito inoculation is the most sensitive method for dengue virus isolation (rx, rx). Isolation rates of up to 100% of serologically confirmed dengue infections are not uncommon, and this is the only method sensitive enough for routine successful virologic confirmation of fatal DHF and DSS cases (rx, rx, rx, rx). Moreover, there are many endemic dengue virus strains that can be recovered only by this method (rx, rx, rx).
Mosquito Cell Culture
- Mosquito cell cultures are the most recent addition to dengue virus isolation methodology (rx, rx, rx, rx, rx). Three cell lines of comparable sensitivity are most frequently used (rx). The first cell line developed, and still the most widely used is the C6/36 clone of A. albopictus cells (76).
- The use of these cell lines has provided a rapid, sensitive, and economical method for dengue virus isolation. Moreover, many serum specimens can be processed easily, making the method ideal for routine virologic surveillance (rx).
- The hybridization probe method detects viral nucleic acids with cloned hybridization probes (rx, rx). Probes with variable specificity ranging from dengue complex to serotype-specific can be constructed depending on the genome sequences used. The method is rapid and relatively simple and can be used on human clinical samples as well as fixed autopsy tissues.
- Unfortunately, hybridization probes have not been widely used or evaluated in the diagnostic laboratory. Preliminary data suggest that this method is less sensitive than RT-PCR, but like PCR, the outcome of the test is not influenced by the presence of neutralizing antibodies or other inhibitory substances.
- Even so, the difficulties of working with RNA and the technical expertise required to obtain reproducible results make this method more suitable as a research tool than as a routine diagnostic test (rx, rx, rx).
- A major problem in dengue laboratory diagnosis has been confirmation of fatal cases. In most instances, only a single serum sample is obtained and serologic testing is therefore of limited value. Also, most patients die at the time of or slightly after defervescence, when virus isolation is difficult.
- With new methods of immunohistochemistry, it is now possible to detect dengue viral antigen in a variety of tissues (rx, rx).
- Although immunofluorescence tests were used in the past, newer methods involving enzyme conjugates such as peroxidase and phosphatase in conjunction with either polyclonal or monoclonal antibodies are greatly improved (rx). Because tissues can be fresh or fixed, autopsies should be performed in all cases of suspected DHF with a fatal outcome (rx, rx).
- The Armed Forces Research Institute of Medical Sciences (AFRIMS) developed an IgM antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA) for dengue in regions where dengue and Japanese encephalitis virus co-circulate[rx[. Today, many groups have developed their own in-house MAC-ELISAs. Dengue-specific IgM in the test serum is detected by first capturing all IgM using human-specific IgM bound to a solid phase.
- An ELISA for dengue-specific IgG detection can be used to confirm a dengue infection in paired sera. It is also widely used to classify primary or secondary infections[rx,rx,rx,rx]. Some protocols use serum dilutions to titer dengue-specific IgG[rx] and others use the ratio of IgM to IgG[rx,rx].
- The assay uses the same dengue antigens as MAC-ELISA and it correlates with results from the haemagglutination inhibition assay.
IgM: IgG ratio
- A dengue virus E and M protein-specific IgM – IgG ratio can be used to distinguish primary from secondary dengue virus infections. IgM capture and IgG capture ELISAs are the most common assays for this purpose. According to this method, a dengue infection is defined as a primary infection if the IgM:IgG OD ratio is greater than 1.2 (using patient sera at 1:100 dilution) or 1.4 (using patient sera at 1:20 dilution), or as a secondary infection if the ratio is less than 1.2 or 1.4 (rxrx,rx).
Nucleic Acid Amplification Tests
- Many nucleic acid amplification tests (NAATs) have been developed for the diagnosis of dengue infection. Some techniques are quantitative and others can be used for serotyping. However, none has been commercialized to date and quality assurance materials are not widely available to ensure the quality of the results.
Treatment of Dengue Fever
For milder forms, treatment includes
- Preventing dehydration – A high fever and vomiting can dehydrate the body. The person should drink clean water, ideally bottled rather than tap water. Rehydration salts can also help replace fluids and minerals.
- Painkillers, such as Tylenol or paracetamol – These can help lower fever and ease the pain.
- Non-steroidal anti-inflammatory drugs (NSAIDs) – such as aspirin or ibuprofen, are not advised, as they can increase the risk of internal bleeding.
More severe forms of dengue fever may need
- Intravenous (IV) fluid supplementation, or drip, if the person cannot take fluids by mouth
- Blood transfusion, for patients with severe dehydration
WHO guidelines summarize the following principles of fluid therapy [rx]
- Oral fluid supplementation must be as plentiful as possible. However, intravenous fluid administration is mandatory in cases of shock, severe vomiting, and prostration (cases where the patient is unable to take fluids orally)
- Crystalloids form the first-line choice of intravenous fluid (0.9% saline)
- Hypotensive states that are unresponsive to boluses of intravenous crystalloids, colloids (e.g., dextran) form the second-line measures
- If the patient remains in the critical phase with low platelet counts, there should be a serious concern for bleeding. Suspected cases of bleeding are best managed by transfusion of fresh whole blood.
The management of patients with dengue infections depends on the phase of illness, i.e. febrile phase, critical/ leakage phase and convalescence phase, as follows:
Rapid Diagnostic Test
- NS1Ag test during the febrile phase (first five days of fever): sensitivity 60–70%, specificity >99%
- PCR – good sensitivity and specificity but expensive and not available in most places
- ELISA- IgM, IgG test – not suitable for early diagnosis because the antibody significantly rises after day 5 of fever
- Reduction of high fever: paracetamol only, tepid sponge
- Promote oral feeding: soft diet, milk, fruit juice, oral rehydration solution (ORS). Avoid IV fluid if there is no vomiting and moderate/ severe dehydration
- Follow up CBC every day
- Advise to come back to the hospital ASAP when there is no clinical improvement despite a lack of fever, severe abdominal pain/ vomiting, bleeding, restless/irritable, drowsy, refusal to eat or drink (some patients may be thirsty), urine not passed for 4–6 hours
2. Critical/ Leakage phase: (Early detection of plasma leakage/ shock)
- Thrombocytopenia, i.e. platelet count ≤ 100,000 cells/mm3, is the best indicator for plasma leakage: Platelet count between 50,000 and 100,000 cells/mm3 – beginning of plasma leakage (about half of DF patients have thrombocytopenia at this level), platelet count < 50,000 cells/mm3 – DHF is most likely and usually indicates that plasma leakage has occurred, probably for 24 hours.
- Admit patients with thrombocytopenia and poor appetite/ poor clinical conditions. Consider admitting high-risk patients: infants, obese patients, patients with prolonged shock (grade IV), bleeding, encephalopathy, underlying diseases, pregnancy.
- Detection of pleural effusion and ascites by a physical examination in the early leakage phase or even at the time of shock is very difficult. Chest film – right lateral decubitus technique, ultrasonography or serum albumin ≤ 3.5 gm% are the alternative ways to detect plasma leakage.
(Proper IV fluid management during the critical period)
- Isotonic salt solution in the critical period, e.g. 5% dextrose in normal saline solution (NSS), 5% Ringer Acetate, 5% Ringer-Lactate. The 5% dextrose in NSS is preferable because the severe cases needing admission are those with poor appetite, nausea/ vomiting, and abdominal pain.
- The total amount of fluid needed during the critical period of 24–48 hours is estimated to be maintenance + 5% deficit (M+5%D), including oral and IV fluids. In DSS patients the duration of IV fluid may be 24–36 hours and in non-shock DHF 48–60 hours.
- The rate of IV fluid should be adjusted according to clinical vital signs (BP, pulse, respiratory rate, temperature), hematocrit (Hct) and urine output (0.5 ml/kg/hr)
- The rate of IV fluid for shock patients (DHF grade III) is shown in Figure [rx]. The IV fluid resuscitation for DHF grade III is less than that recommended for other kinds of shock, i.e. only 10 ml/kg/hr, not 20 ml/kg/hr or over. A larger amount of IV fluid is needed for DHF grade IV, but the rate should be reduced to 10 ml/kg/hr as soon as the blood pressure is restored.
- The rate of IV fluid for non-shock patients (DHF grade I and II) is shown in Figure [rx]. The administration should begin at a slower rate if leakage is in the earlier stage, i.e. platelet count is between 50,000 and 100,000 cells/mm3. The rate of IV should be more rapid when the leakage has continued for some time, i.e. platelet count < 50,000 cells/mm3.
A – Acidosis – blood gas (capillary or venous), if present, check liver and renal functions. Correct acidosis when blood pH is < 7.35 and HCO3 < 15 mEq/L.
B – Bleeding – Hct: if high, dextran is indicated, if low or not rising, consider blood transfusion and consider giving vitamin K1 intravenously.
C – iCa and other electrolytes – Na, K. Give gluconate 1 ml/kg/dose diluted twice with IV fluid and IV push slowly. The maximum dose is 10 ml/dose.
S – Blood sugar
- Colloidal solution – only plasma expander that has an osmolarity higher than that of plasma is recommended, e.g. 10% Dextran-40 in NSS. A bolus dose of 10 ml/kg/hr in children or 500 ml/hr in adults is recommended, and this will usually bring the Hct down to 10 points in cases with signs of fluid overload or persistently high Hct.
- In cases with significant bleeding, i.e. > 6–8 ml/kg ideal body weight in children or 300 ml in adult, blood transfusion is recommended as soon as possible. The amount to transfuse is equal to the estimated amount. If it is impossible to estimate (concealed internal bleeding), transfuse 10 ml/kg of fresh whole blood (FWB) or 5 ml/kg of packed red cells (PRC) in children to raise Hct by 5 points. In adults, transfuse 1 unit of FWB or PRC.
- Platelets are indicated in cases with significant bleeding. If the patient already has signs of fluid overload, however, do not give platelets because this will cause fluid overload (possibly acute pulmonary edema). Platelet transfusion is only adjunct therapy, no specific treatment. There is no platelet prophylaxis in children, no matter how low the platelet count. Clinicians may consider prophylactic platelet transfusion in adults with underlying hypertension or heart disease and a platelet count < 10,000 cells/mm3.
- Plasma has almost no role in the management of acute DHF in the critical phase.
- The steroid has no role in the management of DSS.
- At the children’s hospital, Bangkok, DHF/DSS patients were treated with NSS (100%), Dextran-40 (20–25%), blood transfusion (10–15%) and platelet transfusion (0.4%) [rx].
3. Convalescence phase
- Stop IV fluid when there are signs of recovery: convalescence rash, itching, increase in appetite or > 30 hours after shock and > 60 hours after plasma leakage. Sinus bradycardia may be observed in some patients.
- Patients who have massive ascites and pleural effusion may need diuretic during this period of reabsorption of extravasated plasma into the circulation.
- Some patients may not regain their appetite in this period. This may be due to diuresis and loss of potassium in the urine. A potassium supplement may be necessary in this phase. Fruit (bananas, oranges) and fruit juice are rich in potassium and are preferred by most patients.
- In adults, the convalescence period may extend for 2–4 weeks with fatigue.
4. Management of volume overload [rx]
The most common complication in DHF/DSS management is fluid overload, which may lead to heart failure, acute pulmonary edema or even death if not managed properly and timely.
Steps in the management of fluid overload
- Early detection of signs and symptoms of fluid overload.Early signs of fluid overload: puffy eyelids, tachypnea, distended abdomen with abdominal discomfort. Late signs of fluid overload = indication for diuretic (furosemide 1 mg/kg/dose)* : Cough, respiratory distress (dyspnea/ orthopnea), very tense abdomen, wide pulse pressure (some may have narrowing of pulse pressure), strong and bounding pulse, hypertension (reabsorption phase), abnormal lung signs (crepitation, rhonchi, wheezing). A urinary catheter should be inserted in every patient with late signs of fluid overload.
- Know the status of the patient: time after shock or time after plasma leakage. If the patients are still in the leakage phase, dextran bolus is recommended 15–30 minutes before administering furosemide.
- Status of the patient at that time: shock or non-shock. If the patients are in shock state, dextran bolus is recommended for 15–30 minutes before administer furosemide.
- Assessment and correct associated complications: bleeding, electrolyte/metabolic/acid-base disturbance, liver/renal failure?
- Clinicians are urged to measure the vital signs four times at 15-minute intervals after furosemide administration because furosemide acts for less than 1 hour.
5. Management of DHF with encephalopathy [rx]
- Most cases of encephalopathy are observed in DHF patients during or after the critical phase, but it may occur early in the febrile phase. Few cases are found among DF patients. The presentations include behavior change (aggression, violence, vulgar language), consciousness change (irritation, agitation, confusion, hallucinations, coma) and convulsion.
- More than half of DHF patients who present with encephalopathy are cases of prolonged shock and liver/renal failure. The other common causes are hyponatremia, hypoglycemia, and hypocalcemia. Intracranial bleeding, although quite rare, is usually found in DSS patients with prolonged shock and multi-organ failure and occurs very late, i.e. > 3 days aftershock.
Management of dengue encephalopathy is generally the same as that of hepatic encephalopathy, as follows:
Maintain adequate airway oxygenation with oxygen therapy. Intubation may be necessary for patients who are in respiratory failure or semi-coma/ coma.
Prevent/ reduce ICP by the following measures
- Give minimal IV fluid to maintain adequate intravascular volume, ideally, the total IV fluid should not exceed 80% maintenance
- Switch to colloidal solution earlier if Hct continues to rise or a large volume of IV is needed in cases with severe plasma leakage.
- Administer diuretic if indicated in cases with signs and symptoms of fluid overload
- Consider steroids to reduce ICP. Dexamethasone 0.5 mg/kg/day IV every 6–8 hours is recommended.
- Decrease ammonia production: Give lactulose 5–10 ml every 6 hours for induction of osmotic diarrhea. Local antibiotics to eliminate bowel flora. This is not necessary if systemic antibiotics are given.
- Maintain blood sugar level > 60 mg%. Recommend a glucose infusion rate between 4–6 mg/kg/hour.
- Correct acid-base and electrolyte balance, e.g. correct hypo/hypernatremia, hypo/hyperkalemia, hypocalcemia, and acidosis.
- Vitamin K1 IV administration: 3 mg for < 1 year old, 5 mg for < 5 years old and 10 mg for > 5 years old and adults.
- Anti-convulsants should be given for control of seizures; phenobarbital, Dilantin and diazepam IV as indicated
- Transfuse blood, preferably fresh packed red cells as indicated. Other blood components such as platelets and fresh frozen plasma should not be given because the fluid overload may cause increased ICP.
- Empiric antibiotic therapy may be indicated if suspected superimposed bacterial infections occur.
- H2-blockers or proton pump inhibitor may be given to alleviate gastrointestinal bleeding.
- Avoid unnecessary drugs because most drugs have to be metabolized by the liver.
- Consider plasmapheresis or hemodialysis or renal replacement therapy in cases of clinical deterioration.
Medicine that may be used
- Polyoxotungstates and sulfated polysaccharides – show some potential as viral inhibitors. They impair flavivirus adsorption and entry into host cells in vitro, apparently by binding to the cell surface [rx, rx]. Sulfated galactomannans protected mice from lethal YFV infection when inoculated simultaneously with the virus [rx]
- Ivermectin – a broadly used antihelmintic drug, displays specific inhibitory unwinding activity against helicases from several flaviviruses, including YFV, DENV, and WNV with the half maximal inhibitory concentration (IC50) values in the submicromolar range [rx]. Preliminary studies indicate higher binding efficiency with YFV than with DENV. Nevertheless, disappointingly, Ivermectin did not protect hamsters against infection with YFV. Structure-based optimization may result in analogs exerting potent activity against flaviviruses both in vitro and in vivo.
- Doxorubicin – is an antineoplastic antibiotic obtained from Streptomyces peucetius. This antibiotic exhibits in vitro antiviral activity against the YFV17D vaccine strain and the DENV-2 NGC strain. Doxorubicin proved to be cytotoxic in uninfected host cells. However, a novel derivative of doxorubicin, SA-17, showed excellent antiviral activity against DENV and markedly reduced cytopathogenicity [rx]. The dose-dependent anti-DENV activity was confirmed using a dengue reporter virus.
- Flaviviral inhibitory activity – has also been observed with plant extracts. Boesenbergia rotunda (L.) Mansf. Kulturpfl. (BR) is a common spice belonging to a member of the ginger family (Zingiberaceae)? Some of the BR compounds, such as flavonoids and chalcones, have been shown to be pharmaceutically active. The chalcone, cardamon, isolated from BR, was recently reported to exhibit appreciable anti-HIV-1 protease inhibition [rx]. Moreover, inhibitory activity by six compounds isolated from BR has also been demonstrated on DENV-2 virus NS3 protease activity.
|No||Strategy||Developer (s)||Current status|
|1||Live attenuated yellow fever 17D/DENV chimeric vaccine||Sanofi-Pasteur||Phase 3 trials with a tetravalent formulation in DENV endemic countries|
|2||PDK cell-passaged, live attenuated vaccine||WRAIR/GSK||Phase 2 trials with a tetravalent formulation in endemic countries|
|3||Live attenuated DENV Delta-30 mutation and intertypic DENV chimeric vaccines||NIH/Johns Hopkins||Phase 1/2 trials with monovalent formulations completed; tetravalent|
|phase 1 initiated|
|4||Dengue prM-E DNA vaccine||NMRC||Phase 1 with monovalent vaccine completed|
|5||Recombinant 80 % E subunit antigen vaccine||Hawaii Biotech/Merck||Phase 1 with monovalent vaccine initiated|
|6||Purified inactivated vaccine||WRAIR||Phase 1 with monovalent vaccine initiated|
|7||Live attenuated chimeric DENV vaccine||CDC||Phase 1 with monovalent vaccine initiated|
Abbreviations: PDK, primary dog kidney cells; WRAIR, Walter Reed Army Institute of Research; GSK, GlaxoSmithKline Biologicals; NIH, National Institutes of Health; prM-E, membrane-envelope; NMRC, Naval Medical Research Center; CDC, Centers of Disease Control and Prevention
|Live attenuated tetravalent chimeric YF–DEN vaccine||Sanofi Pasteur||Phase II|
|Live attenuated tetravalent viral isolate vaccine||WRAIR and GSK||Phase II|
|Live attenuated chimeric DEN2–DEN vaccine||CDC and Inviragen||Phase I|
|Recombinant E subunit vaccine||Merck||Phase I|
|Live attenuated tetravalent vaccine comprising 3′ deletion mutations and DEN–DEN chimeras||US NIH LID and NIAID||Phase I|
|Subunit recombinant antigen (domain III) vaccine||IPK/CIGB||Preclinical|
|Live attenuated chimeric YF–DEN vaccine||Oswaldo Cruz Foundation||Preclinical|
|Tetravalent DNA vaccine||US NMRC and GenPhar||Preclinical|
|Purified inactivated tetravalent vaccine||WRAIR and GSK||Preclinical|
Travelers can protect themselves by preventing mosquito bites.
Prevent mosquito bites
- Cover exposed skin by wearing long-sleeved shirts, long pants, and hats.
- Use an appropriate insect repellent as directed.
Higher percentages of active ingredient provide longer protection. Use products with the following active ingredients
- DEET – (Products containing DEET include Off!, Cutter, Sawyer, and Ultrathon)
- Picaridin – (also known as KBR 3023, Bayrepel, and icaridin products containing picaridin include Cutter Advanced, Skin So Soft Bug Guard Plus, and Autan [outside the US])
- Oil of lemon eucalyptus (OLE) or PMD – (Products containing OLE include Repel and Off! Botanicals)
- IR3535 – (Products containing IR3535 include Skin So Soft Bug Guard Plus Expedition and SkinSmart)
Always follow product directions and reapply as directed
- If you are also using sunscreen, apply sunscreen first and insect repellent second.
- Follow package directions when applying repellent on children. Avoid applying repellent to their hands, eyes, and mouth.
Use permethrin-treated clothing and gear (such as boots, pants, socks, and tents). You can buy pre-treated clothing and gear or treat them yourself
- Treated clothing remains protective after multiple piles of washing. See the product information to find out how long the protection will last.
- If treating items yourself, follow the product instructions carefully.
- Do not use permethrin directly on the skin.
- Stay and sleep in screened or air-conditioned rooms.
- Use a bed net if the area where you are sleeping is exposed to the outdoors.
- Advocacy, social mobilization and legislation to ensure that public health bodies and communities are strengthened;
- Collaboration between the health and other sectors (public and private);
- An integrated approach to disease control to maximize the use of resources;
- Evidence-based decision making to ensure any interventions are targeted appropriately; and
- Capacity-building to ensure an adequate response to the local situation.
If you are bitten by mosquitoes
- Avoid scratching mosquito bites.
- Apply hydrocortisone cream or calamine lotion to reduce itching.
If you feel sick and think you may have dengue
- Talk to your doctor or nurse if you feel seriously ill, especially if you have a fever.
- Tell them about your travel.
- For more information about medical care abroad, see Getting Health Care Abroad and a list of International Joint Commission-accredited facilities.
- Use acetaminophen. Do not take pain relievers that contain aspirin and ibuprofen (Advil), it may lead to a greater tendency to bleed.
- Get lots of rest, and drink plenty of liquids.
- Avoid spreading the disease by preventing more mosquito bites.
Mosquito repellents – Use a repellent with at least 10 percent concentration of diethyltoluamide (DEET), or a higher concentration for longer lengths of exposure. Avoid using DEET on young children.
Mosquito traps and nets – Nets treated with insecticide are more effective, otherwise, the mosquito can bite through the net if the person is standing next to it. The insecticide will kill mosquitoes and other insects, and it will repel insects from entering the room.
Door and window screens – Structural barriers, such as screens or netting, can keep mosquitos out.
Avoid scents – Heavily scented soaps and perfumes may attract mosquitos.
Camping gear – Treat clothes, shoes, and camping gear with permethrin or purchase clothes that have been pretreated.
Timing – Try to avoid being outside at dawn, dusk, and early evening.
Stagnant water – The Aedes mosquito breeds in clean, stagnant water. Checking for and removing stagnant water can help reduce the risk.
To reduce the risk of mosquitoes breeding in stagnant water
- Turn buckets and watering cans over and store them under shelter so that water cannot accumulate
- Remove excess water from plant pot plates
- Scrub containers to remove mosquito eggs
- Loosen soil from potted plants, to prevent puddles forming on the surface
- Make sure scupper drains are not blocked and do not place potted plants and other objects over them
- Use non-perforated gully traps, install anti-mosquito valves, and cover any traps that are rarely used
- Do not place receptacles under an air-conditioning unit
- Change the water in flower vases every second day and scrub and rinse the inside of the vase
- Prevent leaves from blocking anything that may result in the accumulation of puddles or stagnant water
Prevention and Control According to WHO
At present, the main method to control or prevent the transmission of the dengue virus is to combat vector mosquitoes through:
- Preventing mosquitoes from accessing egg-laying habitats by environmental management and modification;
- Disposing of solid waste properly and removing artificial man-made habitats;
- Covering, emptying and cleaning of domestic water storage containers on a weekly basis;
- Applying appropriate insecticides to water storage outdoor containers;
- Using of personal household protection measures, such as window screens, long-sleeved clothes, repellents, insecticide-treated materials, coils and vaporizers (These measures have to be observed during the day both at home and place of work since the mosquito bites during the day);
- Improving community participation and mobilization for sustained vector control;
- Applying insecticides as space spraying during outbreaks as one of the emergency vector-control measures;
- Active monitoring and surveillance of vectors should be carried out to determine the effectiveness of control interventions.
Careful clinical detection and management of dengue patients can significantly reduce mortality rates from severe dengue.
WHO responds to dengue in the following ways:
- Supports countries in the confirmation of outbreaks through its collaborating network of laboratories;
- Provides technical support and guidance to countries for the effective management of dengue outbreaks;
- Supports countries to improve their reporting systems and capture the true burden of the disease;
- Provides training on clinical management, diagnosis and vector control at the regional level with some of its collaborating centers;
- Formulates evidence-based strategies and policies;
- Develops new tools, including insecticide products and application technologies;
- Gathers official records of dengue and severe dengue from over 100 Member States; and
- Publishes guidelines and handbooks for surveillance, case management, diagnosis, dengue prevention and control for the Member States.
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