Dengue returns to the United States

Abstract

A REPORT BY THE CDC in July 2010 indicates that dengue, a tropical viral infection transmitted by mosquito bite, has returned to the continental United States. From 1946 to 1980, no cases of dengue were reported in the continental United States. Since 1980, only a few cases coinciding with large outbreaks in Mexico have been confirmed along the Texas-Mexico border.1 In September 2009, a 34-year-old woman from Rochester, New York, was diagnosed with dengue after returning from a vacation in Key West, Florida. By the end of 2009, 27 cases had been identified in Key West, and approximately 5% of the Key West population—over 1,000 people—showed evidence of recent exposure to the virus. By the end of June 2010, 12 additional cases had been reported in Key West and the surrounding area. Researchers believe that the disease may be spreading due to climate change and shifts in weather patterns.1 Causing an estimated 50 to 100 million infections and 25,000 deaths worldwide each year, dengue is the most common virus transmitted by mosquito bite.2 The disease is usually benign, but in some cases it can lead to a bleeding diathesis or disseminated intravascular coagulation called dengue hemorrhagic fever (DHF). From 20% to 30% of patients with DHF develop shock (dengue shock syndrome). Children under age 15 make up 90% of DHF cases worldwide; in the United States, DHF occurs in both children and adults.3 Signs and symptoms Common signs and symptoms of dengue include high fever, frontal or retro-orbital headache, arthralgia, myalgia, rash, ecchymoses, mild bleeding from the nose or gums, and ostealgia (which is why dengue is often called "breakbone fever"). Some patients are asymptomatic.4 If dengue progresses to DHF, signs and symptoms include fever lasting 2 to 7 days, and vomiting and severe abdominal pain persisting after the fever has subsided. Increased capillary permeability may lead to ascites and pleural effusions and thrombocytopenia may cause bleeding. If not treated promptly, DHF can lead to circulatory failure, shock, and death.4 Diagnosis of dengue is usually based on the patient's history and clinical status and confirmed by detection of the virus and immunoglobulins (IgM and IgG) in an enzyme-linked immunosorbent assay antibody capture test. A complete blood cell count will show thrombocytopenia, leukopenia, and increased hematocrit.3 Treatment and prevention Dengue isn't transmitted person-to-person, so isolation isn't indicated. No specific medications or vaccines are currently available for dengue (although there is an effort underway to develop a vaccine). Provide supportive care with acetaminophen, rest, and fluids, as prescribed, to ease signs and symptoms. Aspirin is to be avoided. Patients who develop vomiting and severe abdominal pain in the first 24 hours after the fever declines should call 911 or go to the hospital immediately because these are signs and symptoms of DHF. Patients with DHF are treated with aggressive I.V. fluid replacement therapy.4 Four different viruses can cause dengue. Infection with one produces lifelong immunity against reinfection with that virus and short-term (about 9 months), partial cross-protection against the other three. An individual can be infected up to four times during his or her lifetime.5 Although rare, long-term complications from dengue and DHF can occur if rapid treatment isn't initiated. They include brain damage from prolonged shock, myocarditis, encephalopathy, and liver failure. To reduce the risk of dengue and other mosquito-borne diseases, advise patients to eliminate standing water around their homes where mosquitoes can lay eggs. Cover and regularly clean (at least once a week) water containers such as pet bowls, flower planter dishes, water storage barrels, and any other containers that catch rainwater. In the home, check window and door screens for holes where mosquitoes can enter. Proper application of mosquito repellants that contain 20% to 30% DEET on the skin and clothing can help keep mosquitoes from biting.6