Chikungunya Virus Spreads in Western Hemisphere, BU Reports.
A virus initially reported in Tanzania that has spread rapidly through the Caribbean and Central and South America could spread further in the continental United States, which already has seen more than 1,600 cases, according to a new report in the Annals of Internal Medicine co-authored by a BU School of Public Health researcher.
Dr. Davidson Hamer, professor of global health at SPH and a researcher with the Center for Global Health and Development, reported that chikungunya, a mosquito-borne viral pathogen responsible for a febrile illness that is usually accompanied by a rash and severe joint pain, has claimed 153 lives so far, with more than 900,000 suspected cases and 14,700 confirmed cases, many of them in the Dominican Republic and El Salvador.
He and a co-author, Dr. Lin Chen of the travel medicine center at Mount Auburn Hospital, recommended that clinicians advise patients to use antivector measures when traveling to regions with transmission, and to consider chikungunya in the diagnosis of febrile travelers with joint pain and rashes who have visited the Caribbean and Central or South America.
“The effect of chikungunya virus in travelers since its recent arrival in the Western hemisphere underscores the interconnectedness of the continental United States, the Caribbean, and Central and South America,” they wrote.
In 2005 and 2006, an epidemic of chikungunya that began in East Africa spread to several islands in the Indian Ocean. La Réunion, Comoros, Mayotte, and the Seychelles were especially hard-hit, and the virus subsequently traveled to Asian countries bordering the Indian Ocean, Southeast Asia, the Pacific Islands and, most recently, American Samoa.
Travelers from India to Europe introduced chikungunya, resulting in local transmission in France and Italy. In October 2013, chikungunya virus was detected in Saint Martin and rapidly spread to Martinique and Guadeloupe. In the first half of 2014, the outbreak grew in magnitude, affecting nearly every island in the Caribbean. It also was introduced via travelers to several Central and South American countries, Hamer and Chen said.
In the continental United States, 1,616 imported cases have been reported, with autochthonous transmission in southern Florida.
“Given the widespread presence of competent mosquito vectors (Aedes aegypti and Ae. albopictus), it may spread further within the United States,” Hamer and Chen said.
The viral strain responsible for the growing epidemic in the Western hemisphere is the so-called Asian strain, which is less efficiently transmitted by Ae. albopictus mosquitos and more frequently spread by Ae. aegypti mosquitos. Nevertheless, “the combination of two competent mosquito vectors, frequent travel between the Caribbean and Latin and North America, and an immunologically naive human population has set the stage for a continued epidemic with a high attack rate,” Hamer and Chen said.
“Given the relatively widespread presence of both species of Aedes in the United States, risk for further spread in the Southeast is substantial, particularly for autochthonous transmission,” they wrote. But they noted, “In contrast to West Nile virus, a zoonotic pathogen that spreads in a bird–mosquito cycle, transmission of chikungunya is limited to human–Aedes species interactions.”
No antiviral agents are licensed to treat chikungunya, so therapy is supportive, with anti-inflammatory agents. Antivector measures, including use of diethyltoluamide- or picaridin-containing insect repellents during the daytime, help to reduce the risk for exposure from the daytime-biting Aedes species.
Although most symptoms resolve within 7 to 10 days, severe relapsing and debilitating joint pain can persist in some patients, the authors said.