Dengue Fever

Introduction
Background

Dengue, the most common arboviral illness transmitted worldwide, is caused by infection with 1 of the 4 serotypes of dengue virus. Dengue is transmitted by mosquitoes of the genus Aedes, which are widely distributed in subtropical and tropical areas of the world, and is classified as a major global health threat by the World Health Organization (WHO).

Initial dengue infection may be asymptomatic, may result in a nonspecific febrile illness, or may produce the symptom complex of classic dengue fever (DF). A small percentage of persons who have previously been infected by one dengue serotype develop bleeding and endothelial leak upon infection with another dengue serotype. This syndrome is termed dengue hemorrhagic fever (DHF). Some patients with dengue hemorrhagic fever develop shock (dengue shock syndrome [DSS]), which may cause death.

Dengue virus transmission follows two general patterns—epidemic dengue and hyperendemic dengue. Epidemic dengue transmission occurs when dengue virus is introduced into a region as an isolated event that involves a single viral strain. If the number of vectors and susceptible pediatric and adult hosts is sufficient, explosive transmission can occur, with an infection incidence of 25-50%. Mosquito-control efforts, changes in weather, and herd immunity contribute to the control of these epidemics. This is the current pattern of transmission in parts of Africa and South America, areas of Asia where the virus has reemerged, and small island nations. Travelers to these areas are at increased risk of acquiring dengue during these periods of epidemic transmission.

Hyperendemic dengue transmission is characterized by the continuous circulation of multiple viral serotypes in an area where a large pool of susceptible hosts and a competent vector (with or without seasonal variation) are constantly present. This is the predominant pattern of global transmission. In these populations, antibody prevalence increases with age and most adults are immune. Hyperendemic transmission appears to be a major risk for dengue hemorrhagic fever. Travelers to these areas are more likely to be infected than are travelers to areas that experience only epidemic transmission.

Dengue fever–like illnesses were described in Chinese medical writings dating back to 265 AD. Outbreaks of febrile illnesses compatible with dengue fever have been recorded throughout history. In 1789, Benjamin Rush, MD, published an account of a probable dengue fever epidemic that had occurred in Philadelphia in 1780. Rush coined the term breakbone fever to describe the intense symptoms reported by one of his patients. Probable outbreaks of dengue fever occurred sporadically every 10-30 years until after World War II. The socioeconomic disruptions caused by World War II resulted in increased worldwide spread of dengue viruses.

The first epidemic of dengue hemorrhagic fever was described in Manila in 1953. After that, outbreaks of dengue fever became more common. A pattern developed in which dengue fever epidemics occurred with increasing frequency and were associated with occasional dengue hemorrhagic fever cases. Subsequently, dengue hemorrhagic fever epidemics occurred every few years. Eventually, dengue hemorrhagic fever epidemics occurred yearly, with major outbreaks occurring approximately every 3 years. This pattern has repeated itself as dengue fever has spread to new regions.

Although initial epidemics were located in urban areas, increased dengue spread has involved suburban and rural locales in Asia and Latin America. The only continents that do not experience dengue transmission include Europe and Antarctica. In the 1950s, 9 countries reported dengue outbreaks; today, the geographic distribution includes more than 100 countries worldwide. Several of these countries had not previously reported dengue, and many had not reported dengue in 20 years.

Dengue transmission spread from Southeast Asia into surrounding subtropical and tropical Asian countries, southern China and southern Taiwan, the Indian subcontinent and Sri Lanka, and down the island nations of Malaysia, the Philippines, New Guinea, northeastern Australia, and several Pacific islands, including Tahiti, Palau, Tonga, and the Cook Islands. Nepal has not reported dengue transmission. Hyperendemic transmission is reported in Vietnam, Thailand, Indonesia, Pakistan, India, Malaysia, and the Philippines.

Currently, dengue hemorrhagic fever is one of the leading causes of hospitalization and death in children in many Southeast Asian countries, with Indonesia reporting the majority of dengue hemorrhagic fever cases. Of interest and significance in prevention and control, 3 surveillance studies in Asia report an increasing age among infected patients and increasing mortality rate. Since 1982 in Singapore, more than 50% of deaths have occurred in individuals older than 15 years. In Indonesia, young adults in Jakarta and provincial areas make up a larger percentage of infected patients. During the 2000 epidemic in Bangladesh, up to 82% of hospitalized patients were adults, and all deaths occurred in patients older than 5 years.

The epidemiology of dengue fever in Africa is more poorly characterized. Aedes aegypti is present in a large portion of the Middle East and sub-Saharan Africa. Dengue fever is present in 19 countries on the African continent. In a 1993 epidemic in the Comoros, an estimated 60,000 persons were infected with dengue. Of note, no major dengue hemorrhagic fever epidemics have occurred in Africa, despite the fact that all 4 dengue serotypes circulate in the continent. This may be explained by a genetic factor in these populations.

In the Americas, dengue epidemics were rare postwar because Aedes mosquitoes had been eradicated from most of the region through coordinated vector-control efforts. Systematic spraying was halted in the early 1970s because of environmental concerns. By the 1990s, A aegypti mosquitoes repopulated most of the countries in which they had been eliminated.

The first dengue hemorrhagic fever epidemic in the Americas occurred in Cuba in 1981, with 24,000 cases of dengue hemorrhagic fever, 10,000 cases of dengue shock syndrome, and 158 reported deaths. Since then, dengue fever and dengue hemorrhagic fever cases have progressively increased. A aegypti is abundant year-round in most countries in the Caribbean basin. Significant outbreaks of dengue have been reported in 2005 and 2006 in Puerto Rico, the US Virgin Islands, the Dominican Republic, Barbados, Curacao, Cuba, Guadeloupe, and Martinique.

Aedes albopictus, originally from Asia, is now found in limited areas of Brazil, Bolivia, Colombia, the Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Cuba, and the Cayman Islands. A aegypti is present in all countries in South America except Chile. Hyperendemic circulation of all 4 dengue serotypes is present in the northern countries of South America. Brazil (700,000 cases in 2002), Colombia, and Venezuela report the most cases of dengue and dengue hemorrhagic fever, with low-level transmission occurring year-round but with most occurring during periods of epidemic transmission.

In 1986, the first clearly identified local transmission of dengue in the United States occurred in Texas. Carriers of the virus were believed to have crossed the border from Mexico; the local vector population was then infected. Since then, seasonal autochthonous infection has been reported in both Texas and Hawaii.

Two competent vectors, A aegypti and A albopictus, are currently seasonally abundant in some areas of the southwestern and southeastern United States, including Texas, Arizona, New Mexico, Louisiana, Mississippi, Alabama, Georgia, and mid to south Florida. A aegypti has also been reported sporadically in portions of North Carolina, South Carolina, Tennessee, Arkansas, Maryland, and New Jersey. The range of A albopictus extends almost as far north as the Great Lakes. Since many cases of dengue in US citizens occur as a result of endemic transmission in some US territories, the Centers for Disease Control and Prevention (CDC) currently conducts laboratory-based surveillance in Puerto Rico.

Dengue fever does not naturally occur in the European Union and in continental Europe because these areas do not have an appropriate vector population to allow further spread of dengue from viremic patients returning from other countries. As such, the disease is not statutorily notifiable in most member states. However, dengue does occur in several overseas territories of European Union members. In recent decades, reports of dengue infections in long-term expatriates, aid workers, military personnel, immigrants, and travelers returning from the tropics and subtropics have been increasing.

Factors believed to be responsible for dengue's spread include explosive population growth, unplanned urban overpopulation with inadequate public health systems, poor standing water and vector control, climate change (increased virus transmission has been associated with El Niño conditions), and increased international recreational, business, and military travel to endemic areas. All of these factors must be addressed to control the spread of dengue and other mosquito-borne infections.
Pathophysiology

Dengue infection is caused by 1 of 4 related, but antigenically distinct, viral serotypes: dengue virus 1 (DENV-1), dengue virus 2 (DENV-2), dengue virus 3 (DENV-3), and dengue virus 4 (DENV-4). Albert Sabin speciated these in 1944. Each serotype is known to have several different genotypes. Dengue viruses are small, spherical, single-stranded enveloped RNA viruses of the family Flaviviridae, genus Flavivirus.

Infection with one dengue serotype confers lifelong homotypic immunity and a very brief period of partial heterotypic immunity, but each individual can eventually be infected by all 4 serotypes. Several serotypes can be in circulation during an epidemic.

Dengue viruses are transmitted by the bite of an infected Aedes mosquito. Globally, A aegypti is the predominant highly efficient mosquito vector for dengue infection, but A albopictus and other Aedes species can also transmit dengue with varying degrees of efficiency.

Aedes mosquito species have adapted well to human habitation, often breeding around dwellings in small amounts of stagnant water found in old tires or other small containers discarded by humans. Female Aedes mosquitoes are daytime feeders. They inflict an innocuous bite and are easily disturbed during a blood meal, causing them to move on to finish a meal on another individual, making them efficient vectors. Entire families who develop infection within a 24- to 36-hour period, presumably from the bites of a single infected vector, are not unusual.

Humans serve as the primary reservoir for dengue; however, certain nonhuman primates in Africa and Asia also serve as hosts but do not develop dengue hemorrhagic fever. Mosquitoes acquire the virus when they feed on a carrier of the virus. The mosquito can transmit dengue if it immediately bites another host. In addition, transmission occurs after 8-12 days of viral replication in the mosquito's salivary glands (extrinsic incubation period). The mosquito remains infected for the remainder of its 15- to 65-day lifespan. Vertical transmission of dengue virus in mosquitoes has been documented.1 The eggs of Aedes mosquitoes withstand long periods of desiccation, reportedly as long as 1 year, but are killed by temperatures of less than 10°C.

Once inoculated into a human host, dengue has an incubation period of 3-14 days (average 4-7 d) while viral replication takes place in target dendritic cells. Infection of target cells, primarily those of the reticuloendothelial system, such as dendritic cells, hepatocytes, and endothelial cells, result in the production of immune mediators that serve to shape the quantity, type, and duration of cellular and humoral immune response to both the initial and subsequent virus infections. Following incubation, a 5- to 7-day acute febrile illness ensues. Recovery is usually complete by 7-10 days.

Dengue hemorrhagic fever or dengue shock syndrome usually develops around the third to seventh day of illness, approximately at the time of defervescence. The major pathophysiological abnormalities caused by dengue hemorrhagic fever and dengue shock syndrome include plasma leakage and bleeding. Plasma leakage is caused by increased capillary permeability and may manifest as hemoconcentration, as well as pleural effusion and ascites. Bleeding is caused by capillary fragility and thrombocytopenia and may manifest in various forms, ranging from petechial skin hemorrhages to life-threatening gastrointestinal bleeding.

In persons with fatal dengue hepatitis, infection was demonstrated in more than 90% of hepatocytes and Kupffer cells with minimal cytokine response (tumor necrosis factor [TNF]–alpha, interleukin [IL]–2), similar to that seen with fatal yellow fever and Ebola infections.2

Most patients who develop dengue hemorrhagic fever or dengue shock syndrome have had prior infection with one or more dengue serotypes. In individuals with low levels of neutralizing antibodies, nonneutralizing antibodies to one dengue serotype, when bound by macrophage and monocyte Fc receptors, have been proposed to result in increased viral entry and replication, and increased cytokine production and complement activation. This phenomenon is called antibody-dependent enhancement. In addition, certain dengue strains, particularly those of DEN-2, have been proposed to be more virulent, in part because more epidemics of dengue hemorrhagic fever have been associated with DEN-2 than with the other serotypes.
Frequency
United States

In 1998, 90 confirmed or probable cases of dengue fever were imported into the United States, resulting in one fatality. The current estimate is 100 cases per year; however, the true number of dengue fever cases is believed to be higher because reporting is voluntary, many US physicians are not aware of dengue or its manifestations, and the manifestations are often nonspecific.
In 1999, more than 300 cases of dengue fever were reported from Nuevo Laredo, Tamaulipas, Mexico.3 Nuevo Laredo lies directly across the Rio GrandeRiver from Laredo, Texas. At that time, no dengue cases had been reported in Laredo in more than 12 years. Aedes mosquitoes are present in both cities. The Texas Department of Health reviewed 494 patient records from 5 outpatient sites and was able to confirm 11 cases of dengue fever. Mosquito abatement measures were instituted in Laredo, and health care providers were notified of the dengue fever cases. In the latter half of 1999, Laredo-area health care providers identified 161 suspected dengue fever cases and serologically confirmed 18 cases. This report underscores the need for health care providers to be aware of dengue fever and its manifestations and to test for it in appropriate cases.
International

An estimated 2.5-3 billion people in approximately 110 countries worldwide are at risk for dengue infection. Yearly, approximately 100 million people are infected with dengue, and 250,000 individuals develop dengue hemorrhagic fever. Annually, approximately 24,000 deaths are attributed to dengue worldwide. The Pan American Health Organization (PAHO) member states reported twice as many cases of dengue fever and dengue hemorrhagic fever in 1998 as they did in 1997.

A recent 5-year prospective study in Thai children examined the relative economic burden of dengue infection in children on the local population.4 Most disability-adjusted life years (DALYs) lost to dengue resulted from long-duration illness in children who had not been hospitalized. The infecting serotype appeared to be a determining factor of DALYs lost, with DENV-2 and DENV-3 responsible for 30% and 29%, respectively. The mean cost of illness from dengue was significantly higher than that from other febrile illnesses.
Mortality/Morbidity

* Recovery from dengue infection is usually complete. Even patients who meet strict criteria for dengue hemorrhagic fever or dengue shock syndrome usually recover without sequelae.
* The fatality rate associated with dengue shock syndrome varies by country from 12-44%. In a 1997 Cuban epidemic, the fatality rate in patients who met criteria for dengue hemorrhagic fever or dengue shock syndrome was approximately 6%. The mortality rate associated with dengue fever is less than 1%.
* Data from the 1997 Cuban epidemic suggests that, for every clinically apparent case of dengue fever, 13.9 cases of dengue infection went unrecognized because of absent or minimal symptoms.
* Factors that affect disease severity include patient age, nutritional status, ethnicity, the sequence of infection with different dengue serotypes, virus genotype, and the quality and extent of available medical care.

Race

* Dengue affects all races. Some African and Haitian data demonstrate a relative dearth of dengue hemorrhagic fever and dengue shock syndrome during dengue fever epidemics, suggesting that these populations may share a genetic advantage to the virus. This merits further study.

Sex

* Dengue viruses affect both sexes.

Age

* Dengue affects people of all ages. In Southeast Asia, where dengue is hyperendemic, dengue hemorrhagic fever usually affects children younger than 15 years. However, in the Americas, where dengue is becoming progressively hyperendemic, dengue hemorrhagic fever shows no age predilection.

Clinical
History

* Fever in persons with symptomatic dengue fever may be as high as 41°C. The fever typically begins on the third day and lasts 5-7 days, abating with the cessation of viremia. Fever is often preceded by chills, erythematous mottling of the skin, and facial flushing (a sensitive and specific indicator of dengue fever). Occasionally, and more commonly in children, the fever abates for a day and then returns, a pattern that has been called saddleback fever. Patients are at risk for development of dengue hemorrhagic fever or dengue shock syndrome at approximately the time of defervescence. In travelers, symptoms that begin more than 2 weeks after they depart from an endemic area and fever that lasts longer than 10 days are probably not due to dengue.
* Headache is usually generalized. Retroorbital pain is common and is often described as severe.
* Patients may report nausea and vomiting.
* Patients typically describe a maculopapular or macular confluent rash over the face, thorax, and flexor surfaces, with islands of skin sparing. The rash typically begins on day 3 and persists 2-3 days.
* Patients may have severe myalgias, particularly of the lower back, arms, and legs, and arthralgias, especially of the knees and shoulders.
* Hemorrhagic manifestations may range from small amounts of bleeding from the nose or gums to melena, menorrhagia, or hematemesis.
* Abdominal pain is reported; often, abdominal pain in conjunction with restlessness, change in mental status, hypothermia, and a drop in the platelet count presages the development of dengue hemorrhagic fever.
* Patients report fatigue and malaise.
* Patients may report conjunctival injection, sore throat, and cough.
* Cardiomyopathy is reported, with tachycardia during the febrile period and bradycardia and conduction defect. Myocarditis and congestive heart failure are rare.

Physical

* Fever is present.
* Rash is described as follows:
o Up to half of patients with dengue fever develop a characteristic rash.
o The rash is variable and may be maculopapular or macular.
o Petechiae and purpura may develop as hemorrhagic manifestations.
* Conjunctival injection develops in approximately one third of patients with dengue hemorrhagic fever.
* Pharyngeal injection develops in almost 97% of patients with dengue hemorrhagic fever.
* Generalized lymphadenopathy is observed.
* Hepatomegaly is present more often in dengue shock syndrome than in milder cases. Hepatic transaminase levels may be mildly elevated.
* Hemorrhagic manifestations include the following
o Petechiae and bleeding at venipuncture sites are most common.
o Results from a tourniquet test are often positive. This test is performed by inflating a blood pressure cuff on the upper arm to midway between diastolic and systolic blood pressures for 5 minutes. The results are considered positive if more than 20 petechiae per square inch are observed on the skin of the arm.
o Other hemorrhagic manifestations include nasal or gingival bleeding, melena, hematemesis, and menorrhagia.
* Dengue fever presents in a nonspecific manner and may not be distinguishable from other viral or bacterial illness. The PAHO has developed the following case definitions for the diagnosis of dengue fever and dengue hemorrhagic fever or dengue shock syndrome:
o The clinical description of dengue fever is an acute febrile illness of 2-7 days duration associated with 2 or more of the following:
+ Severe headache
+ Retroorbital pain
+ Severe myalgias
+ Arthralgia
+ Characteristic rash
+ Hemorrhagic manifestations
+ Leukopenia
o Laboratory criteria for diagnosis include one or more of the following:
+ Isolation of the dengue virus from serum, plasma, leukocytes, or autopsy samples
+ Demonstration of a 4-fold or greater change in reciprocal immunoglobulin G (IgG) or immunoglobulin M (IgM) antibody titers to one or more dengue virus antigens in paired serum samples
+ Demonstration of dengue virus antigen in autopsy tissue via immunohistochemistry or immunofluorescence or in serum samples via enzyme immunoassay (EIA)
+ Detection of viral genomic sequences in autopsy tissue, serum, or cerebral spinal fluid (CSF) samples via polymerase chain reaction (PCR)
o Cases are classified as suspected if they are compatible with the clinical description.
o Cases are classified as probable if they are compatible with the clinical definition and satisfy one or more of the following criteria:
+ Supportive serology (reciprocal hemagglutination-inhibition antibody titer greater than 1280, comparable IgG EIA titers, or positive IgM antibody test in late acute or convalescent-phase serum specimen)
+ Occurrence at the same location and time as other confirmed cases of dengue fever
o A confirmed case is one that is compatible with the clinical definition and is confirmed by the laboratory.
o Criteria for the diagnosis of dengue hemorrhagic fever include a probable or confirmed case of dengue infection and hemorrhagic tendencies as evidenced by one or more of the following:
+ A positive result from the tourniquet test
+ Petechiae, ecchymoses, or purpura
+ Bleeding from the mucosa, gastrointestinal tract, injection sites, or other sites
+ Hematemesis or melena and thrombocytopenia (<100,000 cells/μL) and evidence of plasma leakage due to increased vascular permeability that manifests as one or more of the following: greater than 20% rise in average hematocrit level for age and sex, greater than 20% drop in hematocrit level following volume replacement compared to baseline, or signs of plasma leakage (eg, pleural effusion, ascites, hypoproteinemia)
o Dengue shock syndrome is diagnosed in cases meeting all of the above criteria plus evidence of circulatory failure, such as the following:
+ Rapid, weak pulse
+ Narrow pulse pressure (<20 mm Hg)
+ Hypotension
+ Cool, clammy skin
+ Altered mental status
* The WHO classification system was recently studied in Indonesian children and was found to have a sensitivity of 86% (95% CI, 76-94) for the detection of dengue shock syndrome.5 The clinical reliability of the WHO criteria was compared with those of several modified systems, which added the above early predictors of compensated shock and considered models using varying combinations of evidence of hemorrhagic tendencies, thrombocytopenia, and hemoconcentration. These modified systems were found to yield higher sensitivities (88-99%) for dengue diagnosis than the WHO classification system and were more in line with clinical determinations made by local expert physicians.
* A recent Belgian study examined predictors of diagnosis in 1962 febrile travelers and expatriates returning from the tropics. After malaria was ruled out, the main predictors of dengue infection included skin rash, thrombocytopenia, and leukopenia.6

Causes

Dengue infection is caused by 1 of the 4 dengue viruses (ie, DENV-1, DENV-2, DENV-3, DENV-4) and is transmitted to humans by the bite of an infected mosquito.
Differential Diagnoses
Arenaviruses
Meningococcal Infections
Ebola Virus
Meningococcemia
Hepatitis, Viral
Orbivirus
Influenza
Rocky Mountain Spotted Fever
Leptospirosis
Sepsis, Bacterial
Lymphocytic Choriomeningitis
Septic Shock
Malaria
Typhus
Meningitis
Yellow Fever
Other Problems to Be Considered

Chikungunya virus
Mayaro fever
Ross River fever
Sindbis virus
Hemorrhagic fever viruses
Early severe acute respiratory syndrome (SARS)
Workup
Laboratory Studies

* Complete blood cell count findings include the following:
o Leukopenia, often with lymphopenia, is observed near the end of the febrile phase of illness. Lymphocytosis, with atypical lymphocytes, commonly develops before defervescence or shock.
o A hematocrit level rise of greater than 20% is a sign of hemoconcentration and precedes shock. The hematocrit level should be monitored at least every 24 hours to facilitate early recognition of dengue hemorrhagic fever and every 3-4 hours in severe cases of dengue hemorrhagic fever or dengue shock syndrome.
o Thrombocytopenia has been demonstrated in up to 50% of dengue fever cases. Platelet counts of less than 100,000 cells/μL are seen in dengue hemorrhagic fever or dengue shock syndrome and occur before defervescence and the onset of shock. The platelet count should be monitored at least every 24 hours to facilitate early recognition of dengue hemorrhagic fever.
* Basic metabolic panel findings include the following:
o Hyponatremia is the most common electrolyte abnormality in patients with dengue hemorrhagic fever or dengue shock syndrome.
o Metabolic acidosis is observed in those with shock and must be corrected rapidly.
o Elevated BUN levels are observed in those with shock.
* Liver function test findings include the following:
o Transaminase levels may be mildly elevated.
o Low albumin levels are a sign of hemoconcentration.
* Coagulation studies may help to guide therapy in patients with severe hemorrhagic manifestations. Findings are as follows:
o Prothrombin time is prolonged.
o Activated partial thromboplastin time is prolonged.
o Low fibrinogen and elevated fibrin degradation product levels are signs of disseminated intravascular coagulation.
* Typing and crossmatching of blood should be performed in cases of severe dengue hemorrhagic fever or dengue shock syndrome because blood products may be required.
* Serum specimens should be sent to the laboratory for serodiagnosis, PCR, and viral isolation. Because the signs and symptoms of dengue fever are nonspecific, attempting laboratory confirmation of dengue infection is important. Serodiagnosis is made based on a rise in antibody titer in paired IgG or IgM specimens. Results vary depending on whether the infection is primary or subsequent. The IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) has become the most widely used assay, although other tests, including complement fixation (CF), neutralization test (NT), hemagglutination inhibition (HI), and IgG ELISA are also used. A recent European study found that, if only a single serum sample is available, a single positive result on ELISA (PanBio IgM or IgG) was found to have a high rate of false positivity and should be confirmed using a second more specific diagnostic technique.7
* Cultures of blood, urine, CSF, and other body fluids should be performed as necessary to exclude or confirm other potential causes of the patients' condition.

Imaging Studies

* Chest radiography: Right-sided pleural effusion is typical. Bilateral pleural effusions are common in patients with dengue shock syndrome.
* Serial ultrasonography
o Ultrasonography has often been suggested as a potentially timely, cost-effective, and easily used modality in the evaluation of potential dengue hemorrhagic fever. Positive sonogram findings include fluid in the chest and abdominal cavities, pericardial effusion, and a thickened gallbladder wall.
o The utility of previous studies was limited because of the use of single studies for evaluation. However, a recent study involving 158 patients examined the role of daily serial ultrasonographic examinations of the thorax and abdomen in the evaluation of patients with suspected dengue hemorrhagic fever.8 Plasma leakage was detected in some patients within 3 days of fever onset. Pleural effusion was the most common sign. Based on ultrasonographic findings, dengue hemorrhagic fever was predicted in 12 patients before hemoconcentration criteria had been met.

Other Tests

* Arterial blood gas should be assessed in patients with severe cases to assess pH, oxygenation, and ventilation.

Procedures

* Large-bore intravenous catheter - For fluid administration
* Central venous catheter
o For fluid administration
o For central venous pressure measurement
* Arterial catheter
o For continuous blood pressure measurement
o For serial arterial blood gas measurement
* Urethral catheterization - May be useful to strictly monitor urine output
Treatment
Medical Care

* Dengue fever is usually a self-limited illness, and only supportive care is required. Acetaminophen may be used to treat patients with symptomatic fever. Aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids should be avoided.
* Patients with known or suspected dengue fever should have their platelet count and hematocrit measured daily from the third day of illness until 1-2 days after defervescence. Patients with a rising hematocrit level or falling platelet count should have intravascular volume deficits replaced. Patients who improve can continue to be monitored in an outpatient setting. Patients who do not improve should be admitted to the hospital for continued hydration.
* Patients who develop signs of dengue hemorrhagic fever warrant closer observation. Patients who develop signs of dehydration, such as tachycardia, prolonged capillary refill time, cool or mottled skin, diminished pulse amplitude, altered mental status, decreased urine output, rise in hematocrit levels, narrowed pulse pressure, or hypotension, require admission for intravenous fluid administration.
* Intravascular volume deficits should be corrected with isotonic fluids such as Ringer lactate solution. Boluses of 10-20 mL/kg should be given over 20 minutes and may be repeated. If this fails to correct the deficit, the hematocrit value should be determined, and, if it is rising, limited clinical information suggests that a plasma expander may be administered. Starch, dextran 40, or albumin 5% at a dose of 10-20 mL/kg may be used. One recent study has suggested that starch may be preferable because of hypersensitivity reactions to dextran.9 If the patient does not improve after this, blood loss should be considered. Patients with internal or gastrointestinal bleeding may require transfusion. Patients with coagulopathy may require fresh frozen plasma.
* After patients with dehydration are stabilized, they usually require intravenous fluids for no more than 24-48 hours. Intravenous fluids should be stopped when the hematocrit level falls below 40% and adequate intravascular volume is present. At this time, patients reabsorb extravasated fluid and are at risk for volume overload if intravenous fluids are continued. Do not interpret a falling hematocrit value in a clinically improving patient as a sign of internal bleeding.
* Patients who are resuscitated from shock rapidly recover. Patients with dengue hemorrhagic fever or dengue shock syndrome may be discharged from the hospital when they meet the following criteria:
o Afebrile for 24 hours without antipyretics
o Good appetite, clinically improved condition
o Adequate urine output
o Stable hematocrit level
o At least 48 hours since recovery from shock
o Absence of respiratory distress
o Platelet count greater than 50,000 cells/μL

Surgical Care

No specific surgical intervention is necessary in patients with dengue fever, dengue hemorrhagic fever, or dengue shock syndrome.
Consultations

* Consultation with an infectious diseases specialist may be helpful in guiding decisions regarding diagnosis and treatment.
* Consultation with a critical care medicine specialist may be helpful when treating patients with dengue hemorrhagic fever or dengue shock syndrome and severe hemorrhagic manifestations or shock.

Diet

* No specific diet is necessary for patients with dengue fever.
* Patients may become dehydrated from fever, lack of oral intake, or vomiting. Patients who are able to tolerate oral fluids should be encouraged to drink oral rehydration solution, fruit juice, or water to prevent dehydration.
* Return of appetite after dengue hemorrhagic fever or dengue shock syndrome is a sign of recovery.

Activity

Bedrest is recommended for patients with symptomatic dengue fever, dengue hemorrhagic fever, or dengue shock syndrome.
Medication

No specific antiviral medication currently is available to treat dengue infections. Single-dose methylprednisolone showed no mortality benefit in the treatment of dengue shock syndrome (dengue shock syndrome) in a prospective, randomized, double-blind, placebo-controlled trial.10

Acetaminophen (paracetamol) is recommended for treatment of pain and fever. Aspirin, other salicylates, and NSAIDs should be avoided.
Analgesics/antipyretics

The treatment of dengue fever is symptomatic and supportive in nature. Bedrest and mild analgesic-antipyretic therapy are often helpful in relieving lethargy, malaise, and fever associated with the disease.
Follow-up
Further Inpatient Care

* Report known or suspected cases of dengue fever, dengue hemorrhagic fever, or dengue shock syndrome to public-health authorities. Such reports should include patient demographics, case classification, date of onset of illness, whether or not hospitalization was necessary, outcome, and recent travel history. When multiple patients are involved, reports should include the number of cases of dengue fever and dengue hemorrhagic fever/dengue shock syndrome stratified by age, number of confirmed cases and serotypes, and number of hospitalizations and deaths.
* Draw serum specimens for diagnosis as soon as possible after the onset of illness or hospitalization and at the time of death or discharge from the hospital. Immediately place specimens on wet ice and send to the laboratory.
* Evaluate and treat patients appropriately for other possible conditions until the diagnosis of dengue fever or dengue hemorrhagic fever/dengue shock syndrome is established.

Further Outpatient Care

* Draw a serum specimen 7-21 days after the acute-phase serum specimen was drawn. Ideally, draw the convalescent-phase serum specimen 10 days after the acute-phase specimen. Immediately place the specimen on wet ice and send it to the laboratory.

Inpatient & Outpatient Medications

* No specific medications are needed for patients with dengue fever or dengue hemorrhagic fever/dengue shock syndrome. In general, patients should continue to take any medications necessary for the treatment of other medical conditions. However, use diuretics, aspirin, NSAIDs, and antihypertensives with caution in patients with dengue hemorrhagic fever because these medications may exacerbate the pathophysiologic derangement associated with dengue hemorrhagic fever. Review the risks and benefits of each medication and decide on an individuals basis whether the medication should be continued.
* The differential diagnoses of dengue fever and dengue hemorrhagic fever/dengue shock syndrome include many conditions that are treatable with specific medications, such as antibiotics. Until such conditions are excluded, they should be treated.

Transfer

* Transfer patients with dengue fever or dengue hemorrhagic fever/dengue shock syndrome when necessary monitoring and treatment cannot be provided in the current unit or facility. Treat patients with dengue shock syndrome in intensive/critical care units.

Deterrence/Prevention

* No vaccine is available for the prevention of dengue infection. Immunogenic, safe tetravalent vaccines have been developed and are undergoing clinical trials. Because immunity to a single dengue strain is the major risk factor for dengue hemorrhagic fever and dengue shock syndrome, a vaccine must provide high levels of immunity to all 4 dengue strains to be clinically useful.
* The only way to prevent dengue virus acquisition is to avoid being bitten by a vector mosquito. This can be accomplished in several ways, as follows:
o Avoid travel to areas where dengue is endemic. This is not an ideal strategy because it would require a person to avoid most tropical and subtropical regions of the world, and many of these regions are popular travel and work destinations.
o Wear N,N-diethyl-3-methylbenzamide (DEET)–containing mosquito repellant.
o Wear protective clothing, preferably impregnated with permethrin insecticide.
o Remain in well-screened or air-conditioned places.
o The use of mosquito netting is of limited benefit, as Aedes are day-biting mosquitoes.
o Eliminate the mosquito vector using indoor sprays.
o Eliminate the breeding ground of the mosquitoes by not allowing them access to small accumulations of stagnant water around human habitats. Such accumulations can be found in pots, old tires, or any vessel capable of holding water.
* Support community-based vector control programs.

Complications

* Neurologic manifestations such as seizures and encephalitis/encephalopathy have been reported in rare cases of dengue infection. Some of these cases did not manifest other typical features of dengue infection. Other neurological complications associated with dengue infection include neuropathies, Guillain-Barré syndrome, and transverse myelitis.
* Liver failure has been associated with dengue hemorrhagic fever/dengue shock syndrome epidemics. Whether this is a viral effect or a product of prolonged liver hypoperfusion remains unclear.
* Overhydration is a well-recognized complication of dengue fever and dengue hemorrhagic fever/dengue shock syndrome.
* Dengue must be carefully differentiated from pre-eclampsia during pregnancy. An overlap of symptoms and signs, including thrombocytopenia, impaired liver function, capillary leak, ascites, and decreased urine output may make this clinically challenging. Definitive diagnosis is confirmed via serology. Pregnant women with dengue fever respond well to the usual therapy of fluids, rest, and antipyretics. If the mother acquires infection in the peripartum period, newborns should be evaluated for dengue with platelet counts and serologic studies.

Prognosis

* The prognosis of patients with dengue fever is excellent, with complete recovery being the norm. Patients with dengue hemorrhagic fever or dengue shock syndrome who do not die usually recover without sequelae.

Patient Education

* Educate patients, especially those who have experienced prior dengue fever, to avoid mosquito bites when traveling to dengue-endemic areas. Current evidence suggests that those with a history of dengue fever are at highest risk for dengue hemorrhagic fever or dengue shock syndrome if they are infected with a different dengue strain.

Miscellaneous
Medicolegal Pitfalls

* Failure to suspect dengue infection in febrile patients with a history of travel to dengue endemic areas within 2 weeks of the onset of illness
* Failure to suspect, identify, and treat other possible diseases such as meningitis or malaria
* Failure to admit patients with signs and symptoms of intravascular volume loss for intravenous hydration
* Failure to administer appropriate fluids to patients with dengue hemorrhagic fever or dengue shock syndrome
* Failure to notify public health authorities about suspected cases of dengue infection

Special Concerns

* Older patients, particularly those with congestive heart failure, must not be given excessive amounts of intravenous fluids.
* Rare cases of vertical dengue transmission have been reported. Dengue should be suspected in pregnant patients with compatible clinical features. The potential for a neonate to be born with signs and symptoms of dengue fever should be anticipated.