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What are the dangers of chikungunya?

Chikungunya is spreading across the Caribbean, and experts predict that the mosquito borne illness will arrive in the United States in less than two years. What are the dangers of this viral illness? How concerned should Americans be?

The Yellow Fever mosquito is the primary vector transmitting chikungunya in the Caribbean at this time.
The Yellow Fever mosquito is the primary vector transmitting chikungunya in the Caribbean at this time. CDC/Robert S Craig public domain

Chikungunya is a new illness in the Western Hemisphere. It was first detected in Dec. 2013 on French St. Martin. Since then, the infections have spread to many of the islands in the eastern Caribbean, to French Guyana on the South American continent and to the Dominican Republic.

The illness appears about three to seven days after the patient is bitten by an infected mosquito. Chikungunya's symptoms include fever, joint pain which can be severe and may also include headache, muscle aches, joint swelling or a rash. The illness is very rarely fatal and patients usually recover in a week or so.

A large number of patients who recover from chikungunya will experience continuing pain for a period of weeks to years. The Pasteur Institute describes a complication of chikungunya as joint pain of a "subacute or chronic form". It quotes a study from South Africa that found that ten percent of patients still had such pain three to five year after their infection.

A study from 2013 looked at the occurrence and predictors of continuing pain after recovering from chikungunya. It calls the condition "relapsing or lingering rheumatic musculoskeletal pain" and describes it as the hallmark of chikungunya. The data, from 345 adults who had the illness, is not encouraging.

Two years after their chikungunya illness, just 25 percent of the patients had fully recovered. Most of the patients continued to have pain. Nearly half, 43 percent, reported lingering pain while 32 percent reported episodes of relapsing pain. The predictors for "relapsing or lingering rheumatic musculoskeletal pain" due to a chikungunya infection were patient age over 45, female gender and the original severity of the pain during the illness.

Patients with debilitating pain that continues for up to five years will impose costs on both the American health care system and on its economic productivity. An outbreak on Reunion Island in 2005-2006 resulted in 255,000 cases, one third of the population. Martinique, as of April 25, has reported that five percent of its population has become infected.

The chikungunya virus that is spreading in the Caribbean and moving towards continental North and South America is carried by the Yellow Fever mosquito, Aedes aegypti. In the United States, that mosquito's habitat is the southeastern U.S., parts of Texas and parts of southern California. Major American cities such as Houston, Atlanta and Miami are in that zone.

The arrival of locally acquired chikungunya illnesses in the United States should be a cause for alarm. Outbreaks of the disease will leave significant numbers of patients partially or totally disabled for months to years. A large outbreak will have profound effects on economic, healthcare and social systems where it occurs.