Chikungunya virus

Background

Microbiology

• Member of the Alphavirus genus within the Togaviridae family
  • Closely related to o’nyong-nyong virus
• Four genotypes: East-Central-South African, West African, Indian Ocean, and Asian

Epidemiology

• The primary vectors are Aedes aegypti and Aedes albopictus mosquitoes
• Endemic in most of Africa, Southeast Asia, the Philippines, and South and Central America
  • There has been autochthonous transmission in Italy and Frace

Clinical Manifestations

• Incubation period of 1 to 12 days
• Fever, rash, and arthralgias
• Fever may be "saddleback", with remittance at 4 to 8 days followed by recrudescence for 2 weeks
• Arthritis is typically a symmetrical polyarticular arthritis that involves small joints and knees
  • Resolves over months to a year (sometimes longer), but arthralgias (± arthritis) can persist for years
• Rash is macular or maculopapular, and more often central but can involve palms and soles
• Other common symptoms include headache, fatigue, nausea, vomiting, and conjunctivitis
• Bloodwork shows leukopenia, thrombocytopenia, hypocalcemia, and mild to moderate transaminase elevation
• Children are more likely to develop neurological symptoms (status epilepticus, complex seizures, and encephalitis) and dermatologic symptoms (bullous rash)

Differential Diagnosis

Feature	Dengue	Zika	Chikungunya
Asymptomatic	40-80%	35-85%	3-28%
Fever	+++	++	+++
Rash	+	+++	++
Conjunctivitis	–	++	+
Arthralgia	+	++	+++
Myalgia	++	+	+
Headache	++	+	++
Hemorrhage	++	–	–
Shock	+	–	–
Thrombocytopenia	+++	+	–
Leukopenia	++	–	++

Management

• High-dose NSAIDs
• May need aggressive rheumatologic medications for arthritis
• Supportive treatment

Prognosis

• 12% risk of chronic arthralgias up to 3 years post-infection
• Neonates and elderly at highest risk for neurological sequelae