The chikungunya virus infects humans through the bite of a mosquito and causes fever and joint pain. It is rarely fatal, but the symptoms can be severe, long-lasting and debilitating.
Once considered a disease of the tropics, cases have now been documented in more than one quarter of the countries on earth.
This article will discuss the chikungunya virus, its causes, symptoms, treatment and diagnosis; it will also cover ways to avoid the virus.
Contents of this article:
Fast facts on chikungunya virus
Here are some key points about chikungunya virus. More detail and supporting information is in the main article.
- The chikungunya virus is transmitted via female mosquitos
- The major symptoms are fever and joint pain
- The word "chikungunya" means "to walk bent"
- Approximately 96% of people who are infected with chikungunya become symptomatic
- Associated joint pain can last for more than a year
- Chikungunya can only be definitively diagnosed by a blood test
- There are no vaccines for chikungunya
- Complications can include meningitis and nephritis
- Preventing chikungunya comes down to avoiding mosquito-infested areas and preventing contact.
What is chikungunya virus?
Electron microscopy view of chikungunya virus particles.
Image credit: Cynthia Goldsmith, CDC
The chikungunya virus is predominantly transmitted by a bite from an infected female mosquito. In rare cases, the virus can be transmitted through contact with an infected individual's blood.
The virus causes a fever that lasts a few days and joint pain (polyarthralgia) that can last weeks or months (on rare occasions, joint pain can last for a year or more).1
Once the virus has entered the bloodstream, it can divide and multiply within a number of different cell types, including epithelial cells (lining the outside of the body and internal cavities), endothelial cells (lining the inside of blood vessels) and primary fibroblasts (common connective tissue cells).2
Chikungunya is an RNA virus and a member of the Togaviridae family. The disease was first described during an outbreak in Tanzania in 1952.3
Immediately after the first description of the disease, there were a wealth of scientific papers published covering the new condition. This initial interest all but disappeared until a fresh outbreak occurred in and around the Indian Ocean in 2005.
The word "chikungunya" comes from the Makonde (or Kimakonde) language, spoken on the Makonde plateau where the disease was first described. It means "that which bends up," "to become contorted" or "to walk bent over," describing the stooped appearance of patients with joint pain.
Symptoms normally appear between 2 and 7 days after the initial mosquito bite; up to 96% of those who are infected will develop symptoms.4
Currently, there is no vaccine or antiviral treatment, but, in general, the disease is short-lived and rarely fatal. Medication focuses on relieving the symptoms rather than the cause.
Historically, chikungunya was considered a tropical disease because it had only been witnessed in Africa, Asia and India. However, since 2007, outbreaks have occurred in Italy, France, Croatia and the Caribbean islands.
As of April 2015, almost 1.4 million cases have been documented in the Caribbean islands and Latin America. Since 2005, India, Indonesia, Maldives, Myanmar and Thailand have reported over 1.9 million cases. In total, more than 60 countries have identified cases of chikungunya virus within their borders.
Symptoms of chikungunya virus
The symptoms of chikungunya virus normally appear just a few days after an individual has been bitten by a mosquito. The most prevalent symptoms are fever (sometimes as high as 40 °C) and joint pain but may also include headache, muscle pain, rash and swelling around the joints.
The virus is rarely fatal but the symptoms can be severe and disabling. Most patients recover from the fever within a week, but the joint pain has been known to persist for months. Even after 1 year, 20% of patients report recurring joint pain.5
The disease is more serious if contracted by anyone particularly old or young, or those with high blood pressure (hypertension) or diabetes. Any individual who has experienced or is experiencing rheumatic-like symptoms before infection may find the pains return or worsen. These patients are more likely to have longer-lasting rheumatic effects.6
Mortality is predominantly reserved for aging patients.
Diagnosing chikungunya virus
The symptoms of chikungunya virus are similar to those of other diseases such as dengue fever. Only a blood test can definitively diagnose chikungunya.
It is important to rule out dengue fever as quickly as possible because of its higher rate of mortality - up to 50% if untreated, compared with 0.1% for chikungunya.7 If an individual with the symptoms outlined above has recently visited an area where either disease is common, it is advised that medical help should be sought.
On the next page, we look at the treatment of chikungunya, associated complications and treatment.