Chikungunya Has Spread to 1.7 Million Cases in the Americas

Marcia Frellick

October 12, 2015


The number of suspected or confirmed cases of Chikungunya has now reached 1.74 million in 45 countries or territories in the Americas, Marc Fischer, MD, from the Centers for Disease Control and Prevention (CDC), reported here at IDWeek 2015.

Chikungunya is a mosquito-borne alphavirus transmitted primarily by Aedes aegypti and Aedes albopictus mosquitoes. The most common clinical findings are acute fever and severe polyarthralgia, and joint pains can be severe and debilitating. Mortality is rare and occurs mostly in older adults.

"At the peak of the outbreak in the middle of last year, there were 150,000 to 250,000 suspected cases being reported per month," Dr Fischer reported. "Even now, there are over 50,000 cases reported by month."

From December 2013 to December 2014, a disproportionate level of the burden was being borne in the Dominican Republic, according to the Pan American Health Organization.

In addition, "Colombia and El Salvador now account for about a third of the cases and the outbreaks are still going on, although the Colombian Ministry of Health reported in the past 2 weeks that the outbreak has been waning or even ending in that country," said Dr Fischer.

Chikungunya in the United States

Before 2006, Chikungunya was rarely seen in the United States, but by 2013, an average of 28 cases per year was identified. All those infected had traveled to an affected area, mostly in Asia, Africa, and the Indian Ocean Islands. None of these infections resulted in local transmission.

In 2014, after Chikungunya was identified in the Caribbean, there was a significant increase in the number of American travelers infected. Local transmission was then identified in Florida, Puerto Rico, and the US Virgin Islands.

From January 2014 to September 2015, the number of lab-confirmed, travel-associated cases of Chikungunya in the United States rose to 3270. Of the patients diagnosed during those 21 months, 75% had traveled to the Caribbean.

There was also a large escalation in countries reporting infection in mid-2014, from just a few to about 40.

Travel-associated infections have now been identified in almost every state.

Table. States With the Most Travel-Associated Infections Diagnosed From January 2014 to September 2015

State n Percent
New York 863 26
Florida 530 16
California 237 7
Massachusetts 206 6
New Jersey 205 6


But trends are shifting. There are now more cases being reported in American travelers to Mexico, where the first local transmission occurred in April 2014, said Dr Fischer. He said he expects cases to start appearing in border states.

Dr Fischer has disclosed no relevant financial relationships.

IDWeek 2015: Abstract 80. Presented October 8, 2015.


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