What is chikungunya?

Definition

Chikungunya is a relatively rare form of viral infection caused by an alphavirus spread by mosquito bites. It is debilitating but generally nonfatal, with an estimated mortality rate of about one death per one thousand cases.

Causes

Chikungunya is transmitted primarily through two species of mosquito, Aedes aegypti and Aedes albopictus. The mosquitoes become infected when they feed on an infected person during the viraemic period (within five days of the onset of the mosquito bites and symptoms), then transmit the virus to other humans.

Risk Factors

The only known risk factor for chikungunya is an initial exposure to the virus through bites from infected mosquitoes. Before 2013, known outbreaks had occurred primarily in the Eastern Hemisphere, specifically in France, Italy, southern and southeastern Asia, the Arabian Peninsula, central and southern Africa, and various islands in the Indian and Pacific Oceans. In 2013, however, an outbreak of chikungunya in several Caribbean countries marked the first occurrence of the disease in the Americas. Since then, cases have been identified in the United States, Mexico, the Caribbean, Central America, and northern and central South America.

Symptoms

The clinical symptoms of the disease appear within two to twelve days after the initial infection. Symptoms include fever, debilitating joint pains, swelling and stiffness of joints, muscular pain, headache, fatigue, nausea, vomiting, and rash. Many of the clinical symptoms are short in duration, but joint pain can continue for as much as two years after initial infection, in some cases leading to chronic arthritis. Other nonspecific symptoms include conjunctivitis and slight photophobia. Infection with the virus, whether clinically symptomatic or silent, confers lifelong immunity.

Screening and Diagnosis

The common screening and diagnostic confirmation tests for chikungunya include detection of antigens or antibodies in the blood. The common laboratory tests are virus isolation, specific reverse transcription polymerase chain reaction (RT-PCR), and serological tests. The virus isolation test provides the most definitive diagnosis. This technique involves exposing specific cell lines to whole blood samples and identifying chikungunya-specific responses. The RT-PCR uses nested primer pairs to intensify several chikungunya-specific genes from whole blood, while the serological diagnosis uses an enzyme-linked immunoabsorbent assay to measure anti-chikungunya antibody levels of immunoglobulin M and immunoglobulin G.

Treatment and Therapy

There are no specific vaccines or antiviral treatments for chikungunya. Treatments include rest, fluids, and drugs to relieve the symptoms of fever and aching. Commonly used medications include acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen. In cases of long-term joint pain, ribavirin or chloroquine may be used. The use of aspirin or corticosteroids is generally discouraged.

Prevention and Outcomes

The best way to prevent chikungunya is through effective control of the host-agent-environment (HAE) epidemiological triad factors to inhibit the spread of disease vectors—in this case, mosquitoes. HAE control consists of ridding the environment of mosquito breeding sites (such as stagnant water), avoiding mosquito bites, and using screens on windows and doors to keep mosquitoes out of the house. Other preventive measures include using insect repellants on exposed skin and wearing bite-proof long sleeves and trousers.

Bibliography

“Chikungunya Virus.” Centers for Disease Control and Prevention. Dept. of Health and Human Services, 16 Nov. 2015. Web. 29 Dec. 2015.

Peters, Clarence J. “Infections Caused by Arthropod- and Rodent-Borne Viruses.” Harrison’s Principles of Internal Medicine. Ed. Dan L. Longo et al. 18th ed. Vol. 1. New York: McGraw, 2012. 1617–32. Print.

Simon, Fabrice, Elodie Vivier, and Philippe Parola. “Chikungunya: An Emerging Disease in Travelers.” Tropical Diseases in Travelers. Ed. Eli Schwartz. Hoboken: Wiley, 2009. 92–100. Print.

Tolle, Michael A. “Mosquito-Borne Diseases.” Current Problems in Pediatric and Adolescent Health Care 39.4 (2009): 97–140. Print.