Case Study
A 12 year old Hispanic male, whose family was dislocated from the hurricane damaged Corpus Christi, was admitted to Harris Methodist Northwest Hospital in Tarrant County. For the past three days, he has had a frontal headache, retro-ocular pain, muscle and joint pain, nausea, vomiting and a rash. He has a lost of appetite and has not eaten well in the past few days. He had now developed a flushing of the face, neck and chest. He also had developed a mild, dry cough. A confluent petechial rash with round, pale areas of normal skin were found throughout his abdomen. His temperature had reached 103-104 degrees F the past couple of days, with minimum changes with acetaminophen. The patient has gradually grown lethargic.
During the initial physical examination, the oral cavity has shown gingival bleeding, with no other remarkable findings. Abdominal exam revealed a distended, tender abdomen with the liver easily palpable, but very tender and painful. A positive tourniquet test was recorded with 27 petechiae in a square (2.5 x 2.5 cm) patch of skin. Skin turgor showed a delayed response. Blood pressure was 60/40 and falling. The patient's temperature soon began to fall, and he began to sweat profusely. The examination was interrupted with another vomiting episode. Auscultation and chest x-ray showed a pleural effusion. IV fluids and supportive care were quickly initiated.

Medications Ordered:
Promethazine (Phenergan) 12.5 mg pr q 6 hrs prn N/V
APAP 325 mg pr q 4-6 hrs prn fever
Pertinent Labs:
Blood Smear and Gram Stains showed no organisms present
Microscopic Agglutination Test (MAT)- negative
SGOT (AST) 60 (0-40) U/L
LDH 220 (60-200) U/L
SGPT (ALT) 100 (0-50) IU/L
GGT 100 (0-85) U/L

Hepatitis Panel, shows all negative results

WBC 2.8# (3.3-10.5) THSN/CU MM
LY 48 % (17.4-48.2) 1.3#
MO 4 % (4.5-10.5) 0.1#
GR 35 % (43.4-76.2) 1.0#
EO 10 %
BA 3 %

Platelets 75 (144-390) THSN/CU MM
HCT 53% (34.1-49.7)

Protein Total, Serum 4.7 (6-8) G/DL
Albumin 2.5 (3.5-5.5) G/DL

The Texas of Department of Health (TDH) sent notices to all state practitioners about an increase in mosquito-vectored diseases after Hurricane Ayala ravaged the Texan and Mexican Gulf Coast several weeks ago.
Questions

1. What infection could this 12 year old suffering from?
a) Measles
b) Leptospirosis
c) Dengue
d) Malaria
e) Typhoid Fever

An IgM ELISA test for Dengue came out positive, and IgG standard-ELISA microtiter test revealed a four fold rise. Blood serum samples were obtained and sent to the TDH laboratory in Austin for further tests to confirm and differentiate the Dengue serotypes.

2. What Dengue serotype(s) increases the risks for Dengue Hemorrhagic Fever?
a) DEN-1
b) DEN-2
c) DEN-3
d) DEN-4
e) Co-infection of 2 or more serotypes

3. What are the warning signs for impending shock?
a) Intense, sustained abdominal pain
b) Persistent vomiting
c) Restlessness or lethargy
d) Sudden change from fever to hypothermia with sweating and prostration
e) All of the above

4. Which type of hemorrhagic fever is the most severe?
a) Dengue Fever
b) Dengue Shock Syndrome
c) Dengue Hemorrhagic Fever
d) Dengue Death Fever
e) Dengue Influenza

5. How many types of Serotypes of the vaccine are needed to combat Dengue Fever?
a) 1
b) 2
c) 4
d) 8
e) 5

6. Which mosquito is the vector for Dengue Fever?
a) Aedes
b) Culex.
c) Culiseta.
d) Ixodes.
e) Anopheles

7. A common clinical presentation of Dengue Fever is:
a) High Fever
b) Ataxia
c) Tachycardia
d) Non-productive cough
e) Jaundice

8) Why is the IgM ELISA test not a confirmatory test for acute Dengue infection?
a) IgM antibodies may linger in the serum up to 3 months
b) There is a high rate of false negatives from this test.
c) The IgM titers do not raise significantly during infection
d) The IgM ELISA test is not specific for Dengue
e) Answer A and B

9) What is the best prophylaxis for Dengue Fever?
a) Mefloquine (Larium) 250 mg 1 week before travel to endemic areas, and continued weekly during travel, and for 4 weeks after travel.
b) Immunization
c) St. John's Wort
d) DEET sprays, mosquito netting, coverage of exposed skin, and community participation in mosquito control
e) Not going out at night and staying in air conditioned hotels

10) Which States or US territories/commonwealths are endemic to Dengue Fever?
a) Texas
b) Louisiana
c) Mississippi
d) Florida
e) Puerto Rico

Virus Summary

Viral Disease Summary

Dengue Fever is transmitted by mosquitoes of the Aedes family, primarily Aedes Aegypitus. Because of the mode of transmission, Dengue fever is a disease primarily of the tropics. Epidemics occur in the tropics on a 10-30 year basis, although the virus still causes some infection in interepidemic periods.

Dengue belongs to the family Flaviridae and contains four different serotypes: DEN 1, DEN 2, DEN 3, and DEN 4. These different serotypes often cause complications in humans, because infection and subsequent immunity to one virus type does not protect the patient from immunity to the other types. They are morphological similar to togaviruses (enveloped, single stranded (+) RNA with an icosahedral capsid), but slightly smaller, and bud from the internal membranes. They have no visible nuclear capsid, and share similar surface spike antigens. They infect cells of the monocyte-macrophage lineage. Dengue's infection of monocytes (and possibly vascular endothelium) induces the release of cytokines that can lead to complications including shock. Non-neutralizing antibodies can enhance flavivirus infection with Fc receptors on macrophages, which they attach to.

Dengue virus can be found in various animals but causes disease only in humans. Those who live in tropical urban areas (particularly during the monsoon season, when water is more abundant) are most at risk because the mosquito vector feeds primarily on people. The clinical presentation of Dengue Virus includes a high fever, rash, severe arthralgia, and petechiae. Patients may also present with hypotension, hypoproteinemia, hemorrhagic manifestations and hepatic enlargements. In children, the progression to Dengue Hemorrhagic Fever and Dengue Shock Syndrome is characteristic of the following: A relatively mild first phase with abrupt onset of fever, malaise, vomiting, headache, anorexia, and cough which may be followed by rapid deterioration and collapse. Patients often have cold, clammy extremities and a flushed face. The crisis period generally only lasts for 24-36 hours and convalescence is fairly rapid in children who recover. Fatalities associated with Dengue Fever are rare.

Treatment
Patients with DF require rest, oral fluids to compensate for losses via diarrhea or vomiting, analgesics, and antipyretics for high fever (acetaminophen, but not aspirin so that platelet function will not be further impaired). With the earliest suspicion of threatened severe illness, an intravenous line should be placed in so that fluids can be provided. Treatment also includes monitoring blood pressure, hematocrit, platelet count, hemorrhagic manifestations, urinary output, and level of consciousness are important. The hemorrhaging part only lasts 1-2 days. Because the patients has a loss of plasma due to the hemorrhaging, isotonic solutions and plasma expanders, such as Ringer's acetate or Ringer's lactate, plasma protein fraction, and dextran 40. A bolus of 10-20 ml of an isotonic solution per kg bodyweight is give in the case of shock, and repeated every 30 min until circulation improves and urinary output is adequate.

Control and Prevention
An effective vaccine has not yet been produced but is in the making in Thailand. Human volunteers have not been injected yet, but experts estimate one will be population ready in 5-10 years. It will be tetravalent for all four types of DHF and is currently undergoing phase I and II trials.
The vector that needs to be controlled in the Aedes mosquito vector. With no new mosquito control technology available. Mosquito control use to be virtually non existent in most Dengue epidemic countries. However, projects to reverse the mosquito populations teach methods to reduce larval breeding sources. This approach is more likely to be effective in the long run, but not in the near future. We must develop improved methods of providing early warning signs of an impeding epidemic and at least be able to alert the public to take action and prepare physicians to diagnose the disease if an epidemic arises.

SPECIFIC AND CONFIRMATIVE TEST(S)

Virus Detection Methods
Serum is the specimen of choice for both virological and serological studies. Virus remains detectable in the blood on the average of 5 days after the onset of symptoms, and is rapidly cleared upon the appearance of a specific antibody. In diagnostic samples, the virus is stable up to 5 days at approximately 39 degrees F. The sample can be frozen at -76 degrees F or lower. After incubation, the cells are stained with fluorescein-conjugated polyclonal antibodies to detect viruses, when are then serotyped with monoclonal antibodies in an indirect fluorescent antibody test. PCR may shorten the time required for the results, but the PCR test is experimental and no commercial products are available.

Serology
The presence of IgM antibody or a rise in IgG antibody titer to Dengue is diagnostic. IgM antibody can be detectable during the acute phase of the illness, and over 90 percent of patients are IgM positive by the 6th day after onset of symptoms. IgM can also be detected up to around 60 days after infection. IgM capture ELISA is the most widely used test. IgG titers can also be measured by ELISA and hemagglutination inhibition tests. However these techniques cannot differentiate between the four Dengue serotypes.
In primary dengue, the IgG antibody begins to appear by the fifth day after onset of symptoms. The titers rise slightly for a few weeks, then remain detectable for many years. Secondary infections, IgG antibodies are present in early acute serum samples, and titers rise rapidly in a few days.

SPECIFIC DIAGNOSIS OF ILLNESS
Clinical Diagnosis
There are several common levels of manifestations of Dengue fever(DF). The most common is the febrile state, which is minimally symptomatic. It is identified by frontal headache, retro-ocular pain, muscle and joint pain, nausea, vomiting, and a maculo papular rash. Also, there maybe a history of a mosquito bites, or outdoor activity. These symptoms usually lasts 5-7 days and may leave the patient feeling tired after that.
Dengue Hemorrhagic fever (DHF) is an illness that began in south-east Asia and is far much easier to diagnose. DHF begins with a sudden rise in temperature, 38-40C, and other symptoms resembling DF for 2-7 days. After that it may progress into the next form (see information below). It also manifests minor or major bleeding associated with a evidence of plasma leakage documented by hemoconcentration (hematocrit increased by at least one-fifth or decreased by the same amount after intravenous fluid therapy). This disease is most easily identified by the tourniquet test. Petechiae, easily bruised skin, and subcutaneous bleeding at venous puncture sites are present in most cases.
Dengue Shock Syndrome (DSS) is defined as DHF with signs of circulatory failure, including narrow pulse pressure (<or=to20 mm Hg), hypotension, or frank shock. The liver may be palpable and tender; and liver enzymes are usually mildly abnormal but jaundice is rare. The four warning signs for impending shock are intense, sustained abdominal pain; persistent vomiting; restlessness or lethargy; and a sudden change from fever to hypothermia with sweating and prostration. The development of any of these signs or any suggestion of hypotension are indications for hospital admission and management to prevent shock.

Virology Lab Test Results
With acute phase samples, isolation of virus in tissue culture is 50 percent sensitive and the serology may be negative due to insufficient time for the antibody development. Thus, negative results cannot rule out diagnosis of Dengue, and later samples must be drawn. IgM is 90 % sensitive, but IgM antibody may be persistent for 3 months, and may be due to an earlier infection. ELISA tests can cross react with other flaviviruses as well. Samples positive for IgM alone, are not confirmatory for current infection and are reported as possible Dengue. A diagnosis of confirmed Dengue, the virus should be identified by isolation, immunohistochemistry in necrotic tissue, or there should be a four-fold rise in antibody titer, using a type specific plaque reduction neutralization test. The virus isolation during acute phase usually requires a week of incubation, and would not be detected if it was less than 5 days after onset of symptoms.
The high rate of false-negative results on acute serum means that serological tests should not be solely depended upon for treatment and diagnosis.

This Case Presentation was prepared by Victor Armstrong, Stacy Brewer, and Eddie Chen