Friday, July 18, 2014

First Locally Acquired Cases Of Chikungunya Reported in Florida

Aedes aegypti. Credit: University of Florida Entomology & Nematology

MIAMI, Florida -- The Florida Department of Health confirmed on Thursday the first cases of the mosquito-borne disease, chikungunya, that were locally transmitted in the continental United States.  Local transmission means that mosquitoes in the area have been infected with the virus and are spreading it to people

One case was reported in Miami-Dade County and the other in Palm Beach County. Chikungunya is a disease spread by bites from infected Aedes aegypti or Aedes albopictus mosquitoes.  If a person is infected and bitten by a mosquito, that mosquito may later spread the infection by biting another person.

“The Department has been conducting statewide monitoring for signs of any locally acquired cases of chikungunya.” said Dr. Anna Likos, State Epidemiologist and Disease Control and Health Protection Director. “We encourage everyone to take precautions against mosquitoes to prevent chikungunya and other mosquito-borne diseases by draining standing water, covering your skin with clothing and repellent and covering doors and windows with screens.”

Since 2006, the United States has averaged 28 imported cases of Chikungunya virus (CHIKV) per year in travelers returning from countries where the virus is common. To date this year, 243 travel-associated cases have been reported in 31 states and two territories.   However, these newly reported cases represent the first time that mosquitoes in the continental United States are thought to have spread the virus to a non-traveler. 

“The arrival of chikungunya virus, first in the tropical Americas and now in the United States, underscores the risks posed by this and other exotic pathogens,” said Roger Nasci, Ph.D., chief of the U.S. Center for Disease Control’s Arboviral Diseases Branch. “This emphasizes the importance of CDC’s health security initiatives designed to maintain effective surveillance networks, diagnostic laboratories and mosquito control programs both in the United States and around the world.”'

It is not known what course chikungunya will take now in the United States. CDC officials believe 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.  Florida has had the most number of imported cases this year at 73, followed by New York with 20.

CHIKV is spread by two mosquito species: Aedes aegypti (primarily) and Aedes albopictus, both found in Florida. Introductions of the mosquito-borne virus to Florida are possible when a CHIKV infected visitor or returning traveler is bitten by Florida mosquitoes in the early stages (the first week) of their illness.  Infected mosquitoes can then spread the virus to other people they bite.

Since CHIKV is new to the Americas, most people in the region are not immune. This means that people in Florida can be infected and spread the virus to other mosquitoes.  To make matters worse, a person could become infected with both dengue and CHIKV at the same time because they are both carried by the same types of mosquitoes.

Chikungunya Signs and Symptoms

An infected person will typically become ill three to seven days after the mosquito bite, but symptoms can begin anywhere from two to 12 days post-bite. These symptoms can last 3-10 days.

Up to 28% of people who are infected will not have any symptoms (asymptomatic), although they can still be infectious to mosquitoes for a short time if bitten. Persons at greatest risk for severe illness include newborn infants, those over 65 years of age, and those who have other health conditions. Treatment is symptomatic or supportive.

Symptoms may include:
  • Sudden high fever (usually >102ยบ F) which may be continuous or intermittent
  • Severe joint pain that commonly involves the hands and feet
  • Joint swelling
  • Back pain
  • Rash usually 2-5 days after fever starts
  • Other symptoms may include headache, body ache, nausea, vomiting, and redness around the eyes. In unusual cases, infection can involve the brain, eyes, heart, kidney and other organs. 
  • Fatal infections are rare, however many patients have chronic joint pain, arthritis, loss of energy and depression lasting weeks to years.