Chikungunya
Chikungunya is a viral infection caused by an alphavirus, primarily transmitted through the bites of infected mosquitoes, particularly Aedes aegypti and Aedes albopictus. While it is debilitating and associated with significant joint pain, Chikungunya is generally nonfatal, with an estimated mortality rate of about 0.1%. Symptoms typically emerge within two to twelve days post-infection and may include fever, severe joint pain, fatigue, and rash, with joint pain sometimes persisting for up to two years. The disease has had notable outbreaks since the 1950s, primarily in the Eastern Hemisphere, but it has spread to the Americas since a 2013 outbreak in the Caribbean.
Risk factors for severe disease include being a newborn or an older adult with preexisting health conditions. Although there are no specific antiviral treatments or vaccines widely available, supportive care with rest, fluids, and pain relief is recommended. Prevention focuses on controlling mosquito populations and avoiding bites, such as eliminating standing water and using insect repellent. In 2023, the FDA approved the first vaccine against Chikungunya for adults, indicating ongoing efforts to combat this emerging health concern.
Chikungunya
ANATOMY OR SYSTEM AFFECTED: All
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, which can live in tropical, subtropical, and even temperate areas. 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. Between the 1950s and 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.
Case counts have been increasing globally. By mid-2023, there had been outbreaks in 115 countries. Public health experts attributed the increasing prevalence to climate change–related factors (hotter temperatures, wider mosquito ranges, longer warm seasons, higher precipitation, and greater humidity), as well as haphazard urbanization and difficulty maintaining anti-mosquito controls during the COVID-19 pandemic.
Those at highest risk of developing severe disease from chikungunya are newborn infants and older adults with preexisting health conditions.
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. Other nonspecific symptoms include conjunctivitis and slight photophobia. The disease can also cause behavioral changes, cognitive impairment and poor recall in infants, post-infectious dementia in adults, encephalitis, and even death.
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.
Infection with the virus, whether clinically symptomatic or silent, confers lifelong immunity.
Because many of their symptoms overlap, chikungunya can be easily mistaken for other mosquito-borne viral illnesses such as dengue fever and Zika virus.
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, using screens on windows and doors to keep mosquitoes out of buildings, and napping under a treated bed net. Other preventive measures include using insect repellents on exposed skin and wearing bite-proof long sleeves and pants.
The US Food and Drug Administration (FDA) licensed VLA1553, the first vaccine against chikungunya, for use in adults in 2023. It is a single-dose injection of a weakened live virus.
Bibliography
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