Chikungunya virus is an RNA virus transmitted by Aedes mosquitoes, especially Aedes aegypti and Aedes albopictus which are common in the tropics. The virus is endemic in Africa, India, Southeast Asia, and the Philippines. Large-scale outbreaks occurred during 2005-2007 in the Indian Ocean islands and then spread to western India, Southeast Asia and northern Italy. An outbreak in the Caribbean that started in December 2013 has infected more than 100,000 people. The largest outbreak is in the Dominican Republic. A substantial number of imported cases have been documented in the US and in European travelers returning from endemic areas. CDC has confirmed 25 cases Florida and is monitoring cases, in Arkansas, California, Connecticut, Indiana, Maryland, Minnesota, Nebraska, Nevada, New York, North Carolina, Virginia, Puerto Rico and the U.S. Virgin Islands.
Approximately 80% of infected individuals develop high fever, headache, myalgia and symmetrical joint pain in the wrists, elbows, fingers, knees and ankles. A pruritic, maculopapular rash occurs 4 to 8 days later with concurrent leukopenia. The acute febrile phase usually resolves after one week but incapacitating arthralgia may persist for months in 10 to 15% of people.
The defining clinical characteristic is extreme muscle and joint pain. The virus’ name is derived from a Swahili word that describes the extreme pain that people have as a result of the infection. No specific treatment or vaccine is available for chikungunya virus. Infection is thought to confer life-long immunity. Complications include meningoencephalitis, uveitis, retinitis, myocarditis, hepatitis, nephritis, bullous skin lesions, hemorrhage, myelitis, Guillain-Barré syndrome, and cranial nerve palsies. Vertical transmission has been reported including in utero infections, resulting in fetal deaths, and perinatal infection causing symptomatic disease in neonates.
Diagnostic tests include virus isolation from blood, RT-PCR, IgM-specific antibody by EIA, detection of neutralizing antibody by hemagglutination inhibition assay and demonstration of a rise in serum IgG antibody titer between acute infection and convalescence.
Even though no transfusion transmitted cases have been confirmed, the risk for transmission by blood transfusion is theoretically high because at least 20% of infected individuals may be assymptomatic and high titer viremia can last for approximately a week. There are no current standards on donor deferral periods during a chikungunya outbreak, donor screening questions, or licensed screening tests. Since the outbreak is likely to spread, however, the transfusion community needs to be prepared.
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