Dengue Fever in Florida: Time to Test?

Jill A. Ward, MD, PGY3; Jason C. Sniffen, DO; Vanessa Diaz, MD

Disclosures

March 12, 2013

An 8-year-old Dominican boy presented to the emergency department (ED) after one week of sickness. The patient became ill with fatigue, decreased appetite, decreased activity, runny nose, rash, and mild fevers while on a trip to the Dominican Republic. He had visited a physician in the Dominican Republic and was diagnosed with otitis media and given amoxicillin. He returned to the United States after three days of illness and developed a fever of 104 degrees Fahrenheit at home, leading his mother to bring him to the ED. In the ED, he was found to have a negative influenza screen, negative rapid strep test, urinalysis without evidence of infection, as well as other unremarkable lab tests. He was given one dose of ceftriaxone and sent home to follow up with his PCP in 24 hours. He saw his PCP the next day, was given another dose of ceftriaxone, and sent home. Mom noticed continuous high fever with worsening poor appetite and vomiting, and therefore brought him back to the ED. Fever on arrival to the ED was 104.1 degrees Fahrenheit; repeat labs were unremarkable, and the patient was admitted for observation. During the patient’s stay in the hospital, a throat culture was negative, and other lab tests were negative for CMV, EBV, parvovirus B19, RSV, Adenovirus, and mycoplasma. A test for IgM antibodies to the Dengue Fever virus was positive. The patient developed thrombocytopenia and petechiae, which spontaneously resolved over the next week.

Figure 1.

Picture courtesy of Wikipedia Commons: Aedes albopictus mosquito.

Dengue Fever is a potentially fatal, frequently missed diagnosis with fertile ground in Florida’s mosquito-perfect climate. Currently, 40% of the world’s population lives in areas at risk for transmission of Dengue Fever, and its geographic footprint is expanding. Infection with Dengue is one the leading causes of illness and death in tropical and subtropical areas, with up to 100 million people infected yearly.

Although Dengue has previously been rare in the United States, it is endemic in Puerto Rico, Latin America, Southeast Asia, Indonesia, and sub-Saharan Africa, and has recently spread into Florida. The Florida Department of Health has confirmed both local and imported cases of the mosquito-borne illness. Dengue cases in South America, Central America, Mexico, and the Caribbean quadrupled between 1989 and 2007 and continue to rise, reaching an all-time high in South Florida, Puerto Rico, and the U.S. Virgin Islands in 2010 (the most recent data available). The Centers for Disease Control and Prevention (CDC) recently released a study that revealed over 10% of Key West’s population has been infected with the Dengue Fever virus.

Dengue is caused by a member of the flaviviridae, with four serotypes (DENV 1–4) and is transmitted by mosquitoes (Aedes aegypti and Aedes albopictus) found in tropical and subtropical areas. Infection with one of the four serotypes does not protect against infection with the other serotypes, and repeat infections increase the risk of more severe forms of Dengue (Dengue Hemorrhagic Fever and Dengue Shock Syndrome).

Figure 2.

Picture courtesy of Wikipedia Commons: Aedes aegypti mosquito.

 

There is currently no vaccine and no specific treatment for Dengue Fever (conventional anti-virals do not treat Dengue), and the best defenses are against the vector — mosquito prevention. There are an estimated 50–100 million infections per year with 500,000 hospitalizations due to severe disease, and a fatality rate of 5% — which is reduced to <1% by appropriate supportive therapy.

Early recognition of the disease and supportive treatment can substantially lower the risk of developing severe disease. Symptoms occur 4–7 days after the mosquito bite and last for 3–10 days. Classic Dengue Fever (“break-bone fever”) has symptoms that include headache, high fever, muscle and joint pain, nausea, vomiting, and rash — similar to many other viral illnesses — and thus is often missed in the emergency department. Blood work often shows a low white blood cell count. The greatest dangers from Dengue Fever are forms of the disease called Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS). It is similar to other hemorrhagic fevers, with thrombocytopenia being the hallmark on lab testing.

DHF is currently defined by the following four World Health Organization (WHO) criteria:

  • Fever or recent history of fever lasting 2–7 days

  • Any hemorrhagic manifestation

  • Thrombocytopenia (platelet count of <100,000/mm3)

  • Evidence of increased vascular permeability

Dengue Shock Syndrome is the four above criteria and evidence of shock.

There are three phases of Dengue Fever. First is the febrile phase, lasting 3–7 days. Then the afebrile (critical) phase around the time the fever subsides when the patient may develop severe disease. Symptoms include severe abdominal pain, persistent vomiting, hypothermia, hemorrhagic manifestations, or a change in mental status (irritability, confusion, or obtundation). The patient may also have signs of shock. The last phase is the convalescent phase, leading to recovery.

In June 2012, the CDC announced a test for Dengue Fever. The CDC DENV-1–4 Real-Time RT-PCR Assay was announced as the first nucleic acid diagnostic device for detection and serotyping of the Dengue virus approved by the FDA. The Dengue Fever assay detects DENV serotypes 1, 2, 3, and 4 from human serum or plasma. Although there are no vaccines for Dengue prevention and no medications specifically to treat the disease, timely medical care can reduce the possibility of death from 10% in DHF to 1%, and early identification is helpful in determining the best treatment plan. The assay will also be helpful in epidemiology and surveillance of the disease.

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