Laboratory Diagnosis: Samples of the patient’s serum were obtained and paired acute and convalescent samples were tested by an Enzyme Linked Immunosorbent Assay revealing a greater than fourfold rise in anti-dengue IgM antibody titers . The patient was subsequently diagnosed with dengue fever.

Epidemiology: Dengue fever is caused by four virus serotypes belonging to the genus Flavivirus. The virus is transmitted through the bite of female Aedes mosquitoes. The mosquitoes become infected by biting infected humans during the viremic period which lasts about five days. The Aedes mosquitoes are found most frequently near human habitations and breed primarily in man-made water holding containers such as discarded tires, barrels, flower pots, and cans. Dengue viruses are endemic in the South Pacific, Asia, Caribbean, Mexico, South and Central America, and Africa. There is also a small but significant risk of dengue transmission in the United States. Two mosquito vectors, Ae. aegypti and Ae albopictus, have been found in the U.S. and in several Maryland counties. One of the earliest dengue epidemics occurred in Philadelphia in 1780, and the southeastern U.S. was plagued by dengue through the nineteenth and twentieth centuries. Increased urbanization, rapid population growth, and increased international travel have been implicated in dengue fever outbreaks and, thus, pose a significant public health problem.

Clinical Manifestations and Treatment: Dengue fever is characterized by high fever, headache, myalgia, arthralgia, malaise, and oftentimes a rash. The clinical findings can range from a mild febrile illness to severe complications including hemorrhage and shock. The incubation period for dengue is 2-7 days followed by the abrupt onset of symptoms. Other common clinical findings include nausea, vomiting, conjunctivitis, lymphadenopathy, hepatomegaly, and mild hemorrhagic manifestations such as epistaxis. Unusual complications are myocarditis and neurologic abnormalities such as encephalitis and polyneuropathies. Laboratory abnormalities include leukopenia and thrombocytopenia. Dengue Hemorrhagic Fever (DHF) is a severe form of dengue that is characterized by abnormal hemostasis, vascular permeability, and thrombocytopenia.

Patients with a severe illness including DHF with hypotension are diagnosed with Dengue Shock Syndrome (DSS). The differential diagnosis of dengue fever includes a variety of febrile illnesses such as malaria, scrub typhus, influenza, measles, leptospirosis, rickettsial infections, and bacterial sepsis. There are no specific treatments for dengue infections and no vaccines are available. Dengue fever is usually self-limited with fever lasting 3-7 days. Treatment is primarily supportive. Aspirin should be avoided because of potential bleeding diathesis and the increased risk of Reye’s syndrome associated with dengue. Recovery from infection with one serotype provides long-term homologous immunity, but does not provide cross-protective immunity against other dengue serotypes. Aggressive intravenous fluid replacement is essential in patients with DHF/DSS. Patients with classic dengue fever generally recover while the fatality rate of patients with DSS can be as high as 44%. Appropriately treated DHF cases have a fatality rate of 1% to 2%.

Preventive Measures: The only effective way to avoid dengue infection in endemic areas is to avoid mosquito bites. Travelers can help reduce their risk of infection by remaining in well-screened areas, wearing appropriate clothing (long sleeves, pants), and applying mosquito repellent (DEET). Recently, public health organizations have attempted to introduce community-based programs directed at reducing mosquito breeding sites and providing mosquito netting. Currently, there are no approved dengue vaccines available.

References:

1. Karp BE. Dengue fever: A risk to travelers. Maryland Medical Journal. 46(6):299-302, 1997 July.

2. Schwartz DA. Emerging and Reemerging Infections. Progress and Challenges in the Subspecialty of Infectious Disease Pathology. Archives of Pathology and Laboratory Medicine. 121(8): 776-784, 1997 August.