Chikungunya: Coming to America
By Amesh A. Adalja, MD, FACP, FACEP, January 24, 2014
Last month, the Caribbean island of St. Martin reported cases of the mosquito-borne viral illness chikungunya. This was an important development because, until then, this virus had not been found in the Caribbean. Since being identified in St. Martin, the virus has spread to several other Caribbean islands, and cases now number approximately 500.1
Chikungunya virus is infamous for causing a large outbreak on the Reunion Islands in 2006 (after importation from Kenya) that went on to spread to various nations of Asia and Europe.2 The Aedes mosquito, a vector found throughout both the Caribbean and the US, transmits the virus. This mosquito is also the vector for dengue and yellow fever.2
The usual clinical presentation of chikungunya is a febrile illness with rash and characteristic arthralgias. However, up to 25% of those infected can be asymptomatic. Prior to the outbreak on the Reunion Islands, severe cases were rare, but during that outbreak, unusual presentations (encephalopathy) occurred, and mortality rates climbed. In some cases, symptoms may persist for weeks to months. There is no treatment or vaccine available.2,3
Clinical Suspicion Key
Chikungunya is largely a clinical diagnosis based on the presence of fever and arthralgias in a patient who may have traveled to a region in which chikungunya is present. In the past, the majority of cases in the US were the result of importation from India.4
Confirmatory serological testing for chikungunya is available through a reference lab (Quest), the CDC, and state laboratories. PCR is available through the CDC.4
Tip of the Iceberg?
Given the local transmission of chikungunya in the Caribbean and the percentage of asymptomatic cases, the cases in the Caribbean may herald worse to come. Spread to the US Virgin Islands, Puerto Rico, and the US mainland via infected travelers would not be surprising. And given the presence of the vector mosquito in a large swath of the US, importation by a traveler could spark indigenous transmission—as has occurred with dengue—and should be anticipated.
- Epidemiological update: autochthonous cases of chikungunya fever in the Caribbean region. ECDC. http://www.ecdc.europa.eu/en/press/news/_layouts/forms/News_DispForm.aspx?List=8db7286c-fe2d-476c-9133-18ff4cb1b568&ID=945. Accessed January 22, 2014.
- Thiboutot MM, Kannan S, Kawalekar OU, et al. Chikungunya: a potentially emerging epidemic? PLoS Negl Trop Dis. 2010;e623.
- Sissoko D, Moendandze A, Malvy D, et al. Seroprevalence and risk factors of chikungunya virus infection in Mayotte, Indian Ocean, 2005-2006: a population-based survey. PLoS One. 2008;e3066.
- Gibney KB, Fischer M, Prince HE, et al. Chikungunya fever in the United States: a fifteen year review of cases. Clin Infect Dis. 2011; e121-e126.