Chikungunya Virus (ChikV) - MegaMicro

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Chikungunya Virus (ChikV)

Microbiology > Virology > RNA viruses > Single Stranded RNA viruses > Togavirus
Chikungunya virus

Structure:
• A member of the Togaviridae  family, Alphavirus genus;  also classified as an “arbovirus” as it is spread by arthropod vectors.
• A small virus (45-75 nm) with a positive-sense, single-stranded RNA genome, enveloped, icosahedral capsid.

Epidemiology:
• The name chikungunya (from an African language that translates “that which bends up or stooped walk”) refers to the crippling arthritis associated with infection by this virus.
• Endemic in certain parts of Africa, Asia, Europe, the Americas, Indian and Pacific Ocean islands and Caribbean islands, especially in the rainy season.  In 2014, local transmission was reported in Florida.
• Humans are the primary reservoir; however, primates, birds and other vertebrates may also serve as reservoirs.
• The virus is transmitted by the bite of a mosquito, primarily Aedes aegypti and Aedes albopictus, mosquitoes which also transmit Dengue and Zika viruses.
• The incubation period is 2-6 days (range 1-14 days).

Pathobiology:
• In most instances, this virus is transmitted from mosquitoes to humans.   The virus is spread from a viremic human to a mosquito and then back to a human via the mosquito’s salivary glands.
• Less common modes of transmission include vertical transmission (transmission from mother to child during pregnancy or at birth) and via infected blood products and through organ donation.
• Lymphoid tissues, liver, muscle, synovial tissue and the CNS are able to host viral replication. Macrophages appear to be the main reservoir for persistent virus.
• Once infected, lasting immunity has been reported.

Laboratory diagnosis:
• Serum or plasma samples to detect viral nucleic acid by PCR or viral serologies (IgM/IgG).
• During the first 7 days of illness, Chikungunya viral RNA can often be identified in serum or plasma samples.
• IgM is detectable after 5-7 days, IgG after 7-10 days. Evaluate carefully, as IgM may persist for months and cross-reaction may be seen among similar viruses.
• Early and mild thrombocytopenia and lymphopenia.

Disease manifestations:  
• Acute disease:  The majority of patients will develop symptoms, presenting  with abrupt onset of high fever and significant joint pain.   Other symptoms may include headache, muscle pain, joint swelling, maculopapular rash and/or gastrointestinal symptoms.  Multiple joints may be involved, with arthralgia’s bilateral and symmetrical.  Severe complications may include meningoencephalitis, cardiopulmonary decompensation, renal failure and occasionally death, especially in neonates, patients older than 65 years and with underlying medical problems.

• Chronic disease:  After an improvement in symptoms, patients may relapse, displaying symptoms of general discomfort, fatigue and inflammation of the joints and tendons.

Differential diagnosis:
• This viral infection should be considered in patients with acute onset of fever and polyarthralgia, especially in travelers who recently have returned from areas with known virus transmission.
• The symptoms of Chikungunya virus are similar to those of Dengue and Zika, diseases spread by the same mosquitoes that transmit Chikungunya virus.  
• Other considerations include leptospirosis, malaria, rickettsia, Group A streptococcus, rubella, measles, parvovirus, enteroviruses, adenovirus, other alphavirus infections (e.g., Mayaro, Ross River, Barmah Forest, O’nyong-nyong, and Sindbis viruses), post-infections arthritis, and rheumatologic conditions.

Treatment:
• There is no specific medication to treat Chikungunya virus infection.  Treat symptoms with painkillers and acetaminophen (Tylenol).  Avoid aspirin and non-steroidal anti-inflammatory agents until Dengue has been ruled out to decrease the risk of bleeding.
• Patients with chronic disease should be referred to a rheumatologist for treatment.

Prevention and Control:
• There is no vaccine to prevent chikungunya virus infection.
• Travelers can protect themselves by preventing mosquito bites (protective clothing, screens, bed nets, insect repellant).
• Infected persons may reduce the spread of infection by following precautions to reduce mosquito bites during the first week of illness, when viremia is at its highest.

Related concepts
Chikungunya fever, Togaviridae, Alphavirus, arbovirus, viral arthralgias
 
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