The Rapid Review series is designed to briefly review the key emergency medicine points from a single clinical review paper. The Topic: Dengue Fever
Sahaana a first year family medicine resident at the University of Toronto with an interest in emergency medicine. She completed a Bachelor of Life Science at McMaster University and medical school at the University of Toronto. She is an avid runner and enjoys long distance running in her free time.
What is Dengue Fever?
Dengue fever is a mosquito borne infectious tropical disease caused by the Dengue virus. It is endemic around equatorial regions of Africa, the Americas, South East Asia, and Western Pacific.
How does Dengue Fever present?
Many patients infected by the Dengue virus will be completely asymptomatic. Most symptomatic patients will present with a flu like illness, with fever, headache, pain behind the eyes, myalgias, arthralgias, nausea, and vomiting. A maculopapular rash is present in 50-80% of symptomatic patients. Petechial rashes, epistaxis, and oral mucous membrane hemorrhage can sometimes also occur.
About 5% of patients will present with more severe disease (hemorrhage and hypovolemic shock). It is life threatening in a small proportion of cases (<1%) and can lead to death despite treatment.
What is the course of illness?
There are 3 potential phases of Dengue fever:
- Febrile [duration: 2-7 days]
- High fever (>40 degrees Celsius) associated with headache, arthralgias & myalgias. The pain is often severe, resulting in Dengue’s alternative name: “Break-bone fever”.
- Most individuals recover spontaneously, but some individuals will progress to the critical phase despite resolving fever.
- Critical [duration: 1-2 days]
- Significant diffuse leakage of plasma secondary to endothelial dysfunction which can lead to pulmonary edema, ascites, hypovolemia & shock.
- Significant bleeding can also occur, typically from the GI tract.
- Recovery [2-3 days]
- Occurs in patients who’ve experienced the critical phase and is characterized by resorption of leaked fluid back into the vasculature. The recovery phase can be complicated by fluid-overload. The most significant complication is cerebral edema.
How is Dengue Fever diagnosed?
Dengue fever is a clinical diagnosis based on symptoms and physical exam. Probable diagnosis is based on fever + 2 of the following in people living in or visiting an endemic area:
- Nausea and vomiting
- Generalized pain
- Positive tourniquet test (A blood pressure cuff is inflated for 5 minutes, causing petechia. A positive test is defined as at least 10-20 petechiae per 2.5cm2.)
- Any warning signs of Dengue:
- Severe abdominal pain
- Persistent vomiting
- Mucosal bleeding
- High hematocrit + thrombocytopenia
- Lethargy or restlessness
- Serosal effusion
How do we confirm diagnosis of Dengue?
The diagnosis of Dengue fever can usually be made clinically. Confirmatory testing of Dengue fever can be accomplished with PCR (not widely available due to cost) or serology. Viral antigen is >90% sensitive during the febrile phase. Dengue virus specific antibodies (IgM and IgG) can only be used to confirm the diagnosis during the later stages of the infection (after 5-7 days).
Which populations should we be worried about?
Children are at greater risk for complications even if they have mild symptoms. Other risk factors for severe disease include: female sex, high BMI, high viral load, secondary infection, and co-morbid chronic conditions.
How is Dengue Fever transmitted?
Dengue fever virus is typically transmitted via mosquito species within the genus Aedes. There are 5 different strains of the virus and humans are the primary host of this virus. Patients generally develop lifelong immunity to the infecting strain of the virus, but only short-term protection against the remaining 4 strains. Secondary infection with a different strain of the virus increases the risk of severe complications (hemorrhage and shock).
How is Dengue Fever treated?
Treatment of acute Dengue is supportive and focused on maintaining appropriate fluid balance. Appropriate supportive therapy is essential and has decreased historical morality rates.
Individuals who are will hydrated, tolerate oral fluids, and do not have Dengue warning signs can be managed at home with oral rehydration and close follow-up. There is no anti-viral therapy available.
Management of fluid balance is essential. If IV fluid hydration is required, it is generally only needed for the first 1-2 days of illness. Fluids should be titrated carefully to provide the minimum amount needed to achieve a urinary output of 0.5-1cc/kg/hr, stable vitals and normal hematocrit. It is important to prevent over-hydration and discontinue IV fluids during the recovery phase due to the risk of volume overload.
Transfusion with packed red blood cells or whole blood should be considered early in patients with unstable vital signs and decreasing hematocrit rather than abiding by a transfusion threshold. Invasive medical procedures and non-steroidal anti-inflammatory drugs should be avoided given increased bleeding risk.
Can Dengue be prevented?
The best prevention is limiting exposure to mosquito bites in endemic areas. There is a new vaccine available in some countries with endemic Dengue.
Trivia: Where did the term Dengue originate from?
Theory suggest the term Dengue is derived from the Swahili phase “Ka-dinga pepo” which refers to the disease as being caused by an evil spirit.