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Chikungunya - Why we Worry

By: Kenn Fujioka

June, 2014

In December 2013, the World Health Organization reported the first locally transmitted infections with chikungunya virus in the Western Hemisphere. As of June 2014, nearly 200,000 suspect and confirmed locally acquired cases have been identified in 17 countries or territories in the Caribbean or South America (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).

Chikungunya virus has the potential to cause explosive outbreaks which overwhelm local health care systems. From this graph it is clear that health care agencies in the Caribbean cannot possibly confirm all of the suspect infections which meet the definition of a case. Although the case fatality rate of infections with chikungunya virus is estimated at one per thousand, the impact to a fatality’s loved ones or society cannot be trivialized. Even with this “low” fatality rate, 200 deaths can be expected for every 200,000 cases.

In the United States, chikungunya virus will be transmitted only where Aedes aegypti and Ae. albopictus occur. Unfortunately Ae. albopictus is present in our District. The City of El Monte has a population of 110,000. If we extrapolate the incidence rate from St. Vincent and the Grenadines (pop. = 103,000) to El Monte we can expect over 200 suspect and confirmed cases of chikungunya. For comparison, during the first epidemic caused by West Nile virus in 2004, there was considerable attention given to the 13 cases which were reported from El Monte.

What might actually prevent large outbreaks from occurring in El Monte and the rest of the US is our behavior; we probably spend less time outdoors and are more likely to prevent mosquitoes from entering our homes than the populations of other countries where outbreaks occurred. Our residents are also fortunate to have organized mosquito control with budgets dedicated to managing vectors and continuous education.

Residents can also help the District detect and destroy habitat that supports populations of Ae. albopictus. Preventing locally acquired infections with chikungunya will be a difficult task for everyone; we definitely need help!

Notes from the Field: Chikungunya Virus Spreads in the Americas — Caribbean and South America, 2013–2014