CHIKV

Chikungunya virus (CHIKV) is a mosquito-borne positive-sense RNA virus in the genus Alphavirus, family Togaviridae. It causes chikungunya fever, typically presenting with abrupt fever and severe polyarthralgia that can be prolonged, often with rash and fatigue. CHIKV circulates in a sylvatic African cycle involving non-human primates and forest mosquitos, and in an urban cycle driven by Aedes aegypti and Aedes albopictus, enabling sustained human transmission.

Genome and replication: CHIKV is an enveloped, single-stranded RNA virus about 11.8 kilobases long. Its genome encodes nonstructural proteins nsP1–nsP4 and structural proteins C-E3-E2-6K-E1; replication occurs in the cytoplasm. A subgenomic RNA promotes expression of structural proteins.

Clinical features: Incubation is typically 2–12 days. Acute disease features high fever, severe often symmetric joint pain, sometimes swelling, with rash and malaise. Many recover within weeks, but a substantial minority develop persistent arthralgia lasting months to years. Severe outcomes are more common in older adults or those with comorbidities.

Diagnosis and treatment: Diagnosis relies on RT-PCR during viremia or serology (IgM/IgG) after the first week. There is no specific antiviral therapy. Management is supportive: hydration and analgesia; NSAIDs are usually avoided until dengue is excluded.

Prevention and epidemiology: Prevention focuses on vector control and personal protection to avoid bites. There is no licensed CHIKV vaccine as of 2024; several candidates have reached clinical trials. CHIKV has caused outbreaks in Africa, Asia, and the Indian Ocean, with large epidemics in the Americas since 2013.

History: The virus was first isolated in 1952 in Tanzania. The name chikungunya derives from the Makonde language, meaning “to become contorted,” in reference to severe joint pain.