The Florida Department of Health announced on July 17 that two locally acquired cases of chikungunya have been diagnosed in the state. These are the first non-imported illnesses caused by the mosquito borne virus in the continental United States. One patient is in Miami-Dade County and the other is in Palm Beach County.
The Palm Beach Post is reporting in a story dated July 17 that the patient with chikungunya in Palm Beach County is a 50 year old man. The Miami-Dade patient is a 41 year old women. Neither patient has a recent history of travel to a country where chikungunya exists.
Chikungunya was first noted in French St. Martin at the beginning of Dec. 2013. It has spread across the Caribbean since then, and local cases have been found in several Central and South American countries. Until today's announcement, the only locally acquired U.S. illnesses have been in Puerto Rico and the U.S. Virgin Islands.
Florida has reported the highest number of travel-associated chikungunya illnesses for some weeks. The last report from their arbovirus surveillance program was through July 12. At that time the state had 81 imported cases of the disease. Nearly all of the illnesses were contracted in Haiti or the Dominican Republic.
The Centers for Disease Control, in its press release about locally acquired chikungunya issued today, stated that their experts believe that:
chikungunya will behave like dengue virus in the United States, where imported cases have resulted in sporadic local transmission but have not caused widespread outbreaks. None of the more than 200 imported chikungunya cases between 2006 and 2013 have triggered a local outbreak. However, more chikungunya-infected travelers coming into the United States increases the likelihood that local chikungunya transmission will occur.
The chikungunya virus can only be transmitted by the bite of an infected mosquito. The strain of chikungunya in circulation in the Americas is carried by the Yellow Fever mosquito, Aedes aegypti. This mosquito is highly adapted to humans and feeds almost exclusively from humans. It breeds in containers of fresh water, such as rain water, found close to human habitation or even in homes and other buildings.
The Yellow Fever mosquito is a day feeder, and is notably aggressive. It will move indoors and rest in closets or under tables during the heat of the day.
Florida reported in the July 12 data that Palm Beach County had 13 imported chikungunya cases and that Miami-Dade County had 10. Broward County has experienced the greatest number with 20. That all changes with the first locally acquired cases.