Chikungunya

Chikungunya is an alphavirus infection (CHIKV) transmitted by Aedes aegypti and Aedes albopictus mosquitoes, causing acute fever and severe, often debilitating, polyarthralgia.

• Outbreaks in Africa, Asia, the Indian Ocean islands, the Americas, and southern Europe; Kenya had outbreaks in Mombasa and Lamu.
• Incubation 3 to 7 days. Attack rates in naive populations reach 30 to 75%.
• Mortality is low (about 0.1%) but rises in neonates, the elderly, and people with comorbidities.
• Chronic arthritis occurs in 30 to 40% (lasting months to years).

• Abrupt high fever, severe symmetric polyarthralgia or arthritis (hands, wrists, ankles, feet), myalgia, headache, rash (maculopapular), conjunctivitis, and lymphopenia.
• Atypical severe forms: encephalitis, myocarditis, hepatitis, bullous lesions (infants), and neonatal infection (peripartum).
• Subacute phase (weeks 3 to 12): persistent joint pain and stiffness, tenosynovitis, and Raynaud phenomenon.
• Chronic phase beyond 3 months: arthritis resembling rheumatoid arthritis.

• RT-PCR on serum in the first 5 to 7 days; IgM ELISA after day 5; plaque reduction neutralisation for confirmation.
• Leucopenia, thrombocytopenia (mild), raised CRP and ESR.
• Differentiate from dengue (more severe haemorrhagic features, shock, and prominent thrombocytopenia), Zika, malaria, rubella, parvovirus B19, and Ross River virus.
• For chronic arthritis: rheumatoid factor, anti-CCP, and imaging.

• Acute phase: rest, hydration, paracetamol up to 1 g every 6 hours (maximum 4 g/day); avoid NSAIDs and aspirin until dengue is excluded because of bleeding risk, then NSAIDs for joint pain (naproxen 500 mg twice daily).
• Subacute and chronic arthritis:
  • Prednisolone 10 to 20 mg daily for 5 to 7 days then taper, in severe or refractory subacute arthritis.
  • Hydroxychloroquine 200 mg twice daily.
  • Methotrexate 7.5 to 20 mg weekly (with or without sulfasalazine) for persistent inflammatory arthritis lasting beyond 3 months.
  • Intra articular steroids and physiotherapy.
• Vaccines: live attenuated vaccine (single dose, restricted in older adults and immunocompromised, following safety reports) and a virus like particle vaccine for adults.
• Neonatal infection: intensive care, supportive therapy.
• Vector control and personal protection.