Mosquito-Borne Chikungunya Virus Spreads in the Americas

Laurie Barclay, MD

June 06, 2014

Since December 2013, when the World Health Organization first reported local transmission of mosquito-borne chikungunya virus in the Western Hemisphere, local transmission has been detected in 17 Caribbean or South America countries or territories, according to a report published in the June 6 issue of the Morbidity and Mortality Weekly Report. The disease is seldom fatal but often debilitating, and the concern is that imported cases could spread locally‏. In the 2 weeks preceding May 30, the number of reported cases nearly doubled.

"Chikungunya virus is a mosquito-borne alphavirus transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes," write Marc Fischer, MD, and J. Erin Staples, MD, from the Arboviral Diseases Branch, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention (CDC). "These vectors also transmit dengue virus and are found throughout much of the Americas, including parts of the United States. Humans are the primary amplifying host for chikungunya virus, and most infected persons develop symptomatic disease."

The usual clinical manifestations are acute onset of fever and polyarthralgia with bilateral, symmetric joint pains that may be severe and debilitating. In most patients, symptoms improve within 1 week, but in some, joint pain may persist for months. Death is rare and occurs primarily in older adults.

As of May 30, 2014, 103,018 suspected and 4406 laboratory-confirmed chikungunya cases had been reported from Anguilla, Antigua and Barbuda, British Virgin Islands, Dominica, Dominican Republic, French Guiana, Guadeloupe, Guyana, Haiti, Martinique, Puerto Rico, Saint Barthelemy, Saint Kitts and Nevis, Saint Lucia, Saint Martin, Saint Vincent and the Grenadines, and Sint Maarten.

The CDC defines a suspected case as a patient with acute onset of fever higher then 101°F (>38°C) and severe arthralgia or arthritis not explained by other medical conditions who lives in or has traveled to epidemic or endemic areas within 2 weeks before symptom onset.

A confirmed case also requires laboratory evidence of recent chikungunya virus infection (viral isolation, reverse transcription–polymerase chain reaction, immunoglobulin M antibodies, or at least a 4-fold increase in virus-specific neutralizing antibody titers).

"With the recent outbreaks in the Caribbean and the Pacific, the number of chikungunya cases among travelers visiting or returning to the United States from affected areas will likely increase," the authors write. "These imported cases could result in local spread of the virus in other parts of the United States."

Recommendations for Clinicians

Clinicians should consider chikungunya virus infection in patients with acute onset of fever and polyarthralgia, particularly if they have recently returned from areas with known virus transmission.

The CDC, 3 state health departments (California, Florida, and New York) and 1 commercial laboratory (Focus Diagnostics/Quest Diagnostics) currently perform chikungunya virus diagnostic testing.

Because no specific treatment, vaccine, or preventive drug is currently available for chikungunya virus infection, treatment is palliative, including rest, fluids, analgesics, and antipyretics.

To prevent further transmission, infected persons should be protected from mosquito exposure during the first week of illness.

The best way to prevent chikungunya virus infection is to avoid mosquito bites by indoor use of air conditioning or screens and outdoor use of insect repellents, long sleeves, and pants.

Clinicians should report chikungunya cases to their state or local health department, which should in turn report confirmed chikungunya virus infections to CDC through ArboNET, a national passive surveillance system for arthropod-borne diseases.

"CDC and the Council of State and Territorial Epidemiologists urge health departments to perform surveillance for chikungunya cases in returning travelers and be aware of the risk for possible local transmission in areas where Aedes species mosquitoes are currently active," the report authors conclude.

The authors have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2014;63:500-501. Full text

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