Overview
Chikungunya, also referred to as chikungunya virus disease or chikungunya fever, is a viral illness caused and spread through the bite of infected mosquitoes. It is caused by the Chikungunya virus (CHICV).
The disease clinically resembles dengue fever and Zika (which also spread through mosquito bites), and is characterized by severe, sometimes persistent joint pain, fever, and rash.
There is no specific treatment for chikungunya. Treatment is mainly supportive. It is important that you prevent its spread by eliminating mosquito breeding sites such as stagnant water habitats.
What is the infectious agent and how does chikungunya spread?
Chikungunya is caused by the chikungunya virus (CHIKV), which belongs to the family Togaviridae, genus Alphavirus.
It spreads by the bite of mosquitoes, most commonly Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus, which also transmit dengue and Zika viruses. Co-infections of these viruses are not rare.
They multiply by laying eggs in stagnant water and mostly feed and bite you outdoors, though Ae. Aegypti is also known to feed indoors.
Humans are believed to be the main source of the Chikungunya virus. Therefore, the mosquito usually acquires the virus by biting and sucking the blood of an infected person. The virus then multiply inside the mosquito over several days and then get lodged in the mosquito’s salivary glands.
The mosquito then bites another non-infected person and the virus is transmitted to the noninfected person. The virus replicates in this new host who then becomes a new source of infection. The risk of spreading the virus is most during the first week of the illness.
These chikungunya mosquitoes bite mainly during the day and are most active about two hours after sunrise and a few hours before sunset. However, they can bite you at night if the area is well-lit.
An infected person cannot spread the infection directly to another person by touch or by kissing, coughing, or sneezing, meaning it is not a contagious disease. The disease spreads mainly through the chikungunya mosquito bite.
However, it can also spread by transfusion of infected blood or handling of infected blood such as when drawing blood through the vein of an infected person and handling of infected blood in the laboratory. This can be prevented by the use of sterile gloves.
Rarely, an infected pregnant mother can transmit the infection to the fetus, especially during the second trimester. If the mother is infected during delivery, the baby can get seriously ill. There are no reported incidences of transmission of infection through breastfeeding.
Once infected with the chikungunya virus, the person then acquires lifelong immunity from future infections.
Symptoms
Most people who get infected with the chikungunya virus experience symptoms, which onset 2 to 7 days (range 2–12 days) after the mosquito bite. The symptoms can last for 3 to 10 days.
Up to 28% of people who are infected with the virus will not have any symptoms. However, they can still transmit the virus to a mosquito if bitten and therefore, they can be infectious.
Symptoms include:
- Acute fever. The first symptom to appear is often a high fever of sudden onset. The fever is often more than 102ºF. It may be continuous or irregular.
- Severe joint pain. Joint pain develops with or without swelling especially of the hands and feet joints. More than one joints are affected (polyarthritis) and the pain is often unbearable and causes the person to walk in a stooped manner. The joint pain usually lasts for a few days but may sometimes last for weeks, months, or even years. It can go away and can recur again after two or three months. This is called chronic chikungunya arthritis and affects at least 40% of the infected people. The joints mainly affected are those of the ankles, knees, hips, wrists, elbows, and the metacarpo-phalangeal joints and they are usually bilateral and symmetric. If the joint pain and swelling persist, you should see a rheumatologist to rule out an underlying rheumatoid arthritis.
- Skin rash. About 50% of cases develop a maculopapular rash on the face, neck, back, abdomen, arms, legs, palms, or feet. Skin rash usually appears 2 to 5 days after the onset of fever, but may appear simultaneously when the fever onsets or even after the fever subsides. In about 80% of the cases, the rash is asymptomatic and does not itch. The rest may complain of mild itching of the skin.
Other symptoms include:
- Muscle pain (myalgia)
- Headache
- Weakness
- Fatigue
- Nausea
- Red eyes
- Loss of appetite
You should note that the symptoms of chronic chikungunya arthritis and those of rheumatoid arthritis are similar, leading people to falsely believe that chikungunya causes rheumatoid arthritis. That is not correct; chikungunya does not cause rheumatoid arthritis. It is just that the symptoms of both are similar and both can coexist.
Another factor to note is that an acute CHIKV infection may also aggravate an underlying rheumatic disease with studies showing relapses of rheumatoid arthritis symptoms in patients who were in remission before CHIKV infection.
Recovery time
Most symptoms are generally self-limiting and the majority of the people feel better and recover fully after 1 to 2 weeks with no new symptoms manifesting.
Some others may have joint and muscle pain lasting for months, sometimes even years. This is called chronic chikungunya arthritis. About 40% or even more of those infected with the virus become so affected.
Chikungunya is rarely fatal though the disease can contribute to the cause of death in older people.
Risk factors for chronic and prolonged symptoms
Most people make a full recovery from chikungunya within one week, but occasionally chronic arthritis causing persistent long-term joint pain after a chikungunya infection can also develop, which can be debilitating.
Those at risk for such a more severe chronic chikungunya disease include:
- Newborns
- Older adults 65 years and older
- People with health conditions such as high blood pressure, diabetes, heart disease, respiratory disease, and kidney disease.
- People with osteoarthritis
- Obesity is another independent factor that increases your risk of getting chronic chikungunya arthritis.
Complications
Most people recover fully within one week but occasionally, eye, heart, or neurological complications can develop. Such complications of chikungunya include:
- neurological complications such as encephalopathy and myelitis
- seizures
- myocarditis
- eye complications such as uveitis and retinitis
- hepatitis
- kidney complications such as acute nephritis and abnormal kidney function
- bullous skin lesions
How common is chikungunya?
Worldwide
Chikungunya predominantly is found in the tropical and subtropical regions. It occurs mainly in Africa and Southeast Asia. It was first discovered and identified in the United Republic of Tanzania in 1952 – 1953, although it is suspected to have been present in Africa and Asia from much before. The chikungunya virus was, however, first isolated in Thailand in 1958
Later it spread to other countries in Africa and subsequently to Asia notably in the Philippines, Thailand, Cambodia, Vietnam, India, Burma, and Sri Lanka.
Outbreaks in the cities of Thailand were first recorded in 1967 and in India in the 1970s.
Since 2003, there have been outbreaks in the islands of the Pacific Ocean, notably Madagascar, Comoros, Mauritius, and Reunion Island.
CHIKV has now made its presence felt in over 110 countries in Asia, Africa, Europe, and the Americas.
In 2013, CHIKV spread to the Western Hemisphere. Forty-six countries have recognized local transmission. Presently, it is estimated that 39% of the world’s population lives in CHIKV-endemic countries and faces a risk of getting infected.
The above information provides guidance to those traveling to these areas on how to take the chikungunya vaccine for protection.
In the United States
According To The Centers for Disease Control and Prevention, in 2015, chikungunya became a nationally notifiable condition in the United States; meaning that, when diagnosed, it is required by law that health providers report it to state or local public health officials.
Before 2006, chikungunya was almost undetected in U.S. travelers.
During 2006–2013, an average of 28 people every year in the United States tested positive for fresh chikungunya virus infection. They were all travelers to the United States coming from affected areas in Asia, Africa, or the Indian Ocean.
In late 2013, the first local resident with chikungunya virus infection in the Americas was diagnosed in Caribbean countries indicating that mosquitoes in the area were infected with the virus and causing its spread. This was seen in Florida, Texas, Puerto Rico, and the U.S. Virgin Islands.
Since then, chikungunya has spread throughout the Caribbean and into Central and South America.
Diagnosis
The doctor normally suspects chikungunya when he comes across three telltale symptoms and signs:
- acute fever
- polyarthralgia (multiple joint pains)
- and h/o recent travel to an area where the chikungunya virus is endemic
Laboratory diagnosis of chikungunya is generally performed by testing serum or plasma for the chikungunya virus, viral nucleic acid, or ChickV-specific neutralizing antibodies.
The chikungunya virus can be detected in the serum or plasma during the first week of the illness (the acute phase), using tests such as reverse transcriptase–polymerase chain reaction (RT–PCR).
Subsequently, serologic testing after the first week of illness for antibodies (the body’s autoimmune response to the chikungunya infection) should be performed.
IgM and IgG antibodies to ChikV are normally detectable 6 to 7 days following the onset of symptoms. IgM antibodies usually remain detectable for 3 to 4 months after infection, whereas IgG antibodies remain detectable for years.
So if the acute phase (first 8 days) of the illness has passed, antibody testing should be resorted to because the RT-PCR test may be inconclusive.
It is important to note that a person can simultaneously be infected with CHIK and dengue viruses because both these viruses are carried by the same types of mosquitoes. Testing for both these viral diseases is the only way to differentiate between CHIK and dengue fever.
Treatment
There is no specific antiviral drug treatment for chikungunya. Treatment is mainly supportive and aims primarily to relieve symptoms including fever and joint pain.
- Rest is necessary to recover from weakness
- Drink plenty of oral fluids (water or juices) to stay well hydrated.
- Antipyretics such as acetaminophen can be given to control fever and joint pain.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen should not be used until dengue fever has been ruled out for fear of bleeding. Once dengue has been ruled out through testing, NSAIDS can help with acute fever and joint pain.
- Intravenous fluids and electrolyte replacement help to prevent dehydration.
- For chikungunya patients with persistent joint pain, NSAIDs, oral corticosteroids topical preparations, and physical therapy might help lessen the pain and swelling.
Foods to eat
Vitamin C is a good immune booster, acts as an antioxidant, and can protect your body from toxins that cause inflammation. You should eat foods rich in vitamin C, such as oranges, kiwis, and guava. They are easy to digest and are strongly recommended to patients infected with chikungunya.
Foods to avoid
Avoid
- sugary foods
- bakery products
- caffeinated and effervescent beverages
- alcohol and smoking
- processed foods
- oily and spicy foods
- saturated fat foods such as red meat
Prevention
The mosquitoes lay their eggs and breed in stagnant water. Prevention of chikungunya relies heavily on not allowing stagnant water habitats to exist anywhere in or near the domestic area.
Where water is kept for a long time such as for cattle to drink or outdoor fish tanks, larvicides can be used to kill the eggs laid by the mosquitoes. They are used widely and are relatively safe for cattle and fish and can be used to treat potable water.
During outbreaks, use effective sprays to kill flying mosquitoes and on the likely places of their habitats such as stagnant water, certain likely surfaces, in and around doors and windows of houses through which they can enter the house.
Since these mosquitoes bite during the day, (and on a well-lit night), use clothing that minimizes skin exposure. Apply mosquito repellants on exposed skin during the day and night.
Whenever you sleep, use good mosquito nets, mosquito coils, or other insecticide vaporizers to avoid indoor mosquito bites. Have windows of your home including toilet windows prefitted with nets.
If you are traveling and staying in an area that can increase your risk, you should consider taking the Chikungunya vaccine.
Several chikungunya vaccines are currently under development. One chikungunya vaccine (called IXCHIQ) is available in the United States and is approved for use in adults 18 years and older. It is given as a single dose.
