Chikungunya
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Direct answer
Sudden high fever followed by crippling, symmetric, small-joint polyarthralgia that makes walking and gripping agony, with a maculopapular rash and sometimes photophobia, is chikungunya — an alphavirus (family Togaviridae) transmitted by Aedes aegypti and albopictus, whose name means "that which bends up". There is no specific antiviral and no vaccine: care is analgesic and anti-inflammatory, with the crucial caveat that NSAIDs are withheld until dengue has been excluded in the co-epidemic Indian setting. The defining complication is arthralgia persisting for months to years in a substantial share of adults, which seronegative arthritis mimics — and vertical transmission near delivery causes severe neonatal disease.
What you must remember
- Agent and vector: chikungunya virus, a positive-sense RNA alphavirus; the East-Central-South-African genotype with the E1-A226V mutation adapts to Aedes albopictus and drove the explosive 2006 Indian epidemic of well over a million cases; transmission follows the Aedes season and daylight biting.
- Clinical core: abrupt high-grade fever with chills, severe symmetric polyarthralgia of metacarpophalangeal joints, wrists, ankles and knees with morning stiffness, incapacitating in the first week; maculopapular pruritic rash on the trunk and limbs, retro-orbital pain, photophobia, cervical lymphadenopathy, and conjunctival suffusion.
- Dengue contrast (the bedside exam): chikungunya has crippling arthritis, true rash and photophobia, with platelets near-normal and no plasma leakage or shock; dengue has retro-orbital pain, flushing, significant thrombocytopenia, capillary leak and the critical-phase timeline.
- Diagnosis: RT-PCR in the first week of viraemia; IgM capture ELISA from about day 5, persisting weeks to months — which also means a positive IgM may reflect remote infection; IgM cross-reactivity with other alphaviruses, and co-testing for dengue, is routine practice.
- Treatment: none specific — paracetamol for fever and pain, hydration; NSAIDs only after dengue is excluded (bleeding risk), and short courses for stubborn synovitis thereafter; chloroquine phosphate was studied for chronic arthritis with unconvincing evidence and no routine role; low-dose steroids only for refractory inflammatory cases.
- Chronic phase: arthralgia or inflammatory arthritis persists beyond three months in roughly a third or more of adults, occasionally years — managed as chronic musculoskeletal disease with physiotherapy and analgesia, and often mislabelled seronegative rheumatoid arthritis.
- Neonatal chikungunya: vertical transmission when the mother is viraemic around delivery produces neonatal fever, rash, oedema, seizures and rarely long-term sequelae — the reason obstetric vigilance in the Aedes season matters.
- Rare complications: myocarditis, meningoencephalitis, Guillain-Barre syndrome, hepatitis and cutaneous ulcers; deaths are overwhelmingly attributable to comorbidity rather than direct viral lethality.
How to work through a monsoon-season case
A 38-year-old woman from a dengue-endemic city presents on day 3 of illness with 39 degrees fever, a faint trunk rash and hands too painful to close; multiple neighbours have similar illness. Step one is syndromic honesty: in India this is the dengue-chikungunya season, and the two travel together — so the first order is paired testing (dengue NS1 and IgM alongside chikungunya IgM or PCR) rather than a single diagnosis, because management diverges at exactly one decision, the NSAID. Step two is the analgesic ladder with the safety interlock: paracetamol around the clock for the first days, withholding NSAIDs until platelets are known — in the meantime, the crippling small-joint distribution itself argues for chikungunya, since dengue myalgia is muscular, not articular and deforming-feeling. Step three is severity screening: check for the rare myocarditis (pulse, ECG), meningoencephalitis (sensorium) and, if she is pregnant, establish gestation — the peripartum viraemic window is the dangerous one for the neonate. Step four is the convalescent conversation, the most under-delivered in practice: warn her explicitly that joint pain may smoulder for months, schedule review, and plan graded physiotherapy rather than repeated antibiotic courses for "viral fever that never settled". Step five is vector control as clinical medicine: source reduction around the household, daytime repellent use, and reporting so that municipal vector surveillance responds — the intervention that actually shortens the outbreak.
Where students slip
The dominant slip is taxonomy: chikungunya is an alphavirus (Togaviridae) while dengue and Zika are flaviviruses — a one-mark separator that decides many MCQs. The second is the NSAID trap: prescribing ibuprofen on day 2 of "chikungunya-like" illness before excluding dengue is the planted error, since co-circulation makes dengue the silent co-diagnosis. Third, students assume IgM positivity dates the illness; persistence for months means a positive IgM in a chronically aching patient may be an old fingerprint, not the current cause — PCR or paired serology is the honest timing tool. A quieter viva favourite is the mutation story: the E1-A226V substitution enabling Aedes albopictic transmission explains why the 2006 epidemic exploded — genuine textbook-specific currency.
Frequently asked questions
Which joints and what pattern characterize chikungunya arthralgia?
Symmetric, often crippling involvement of small peripheral joints — metacarpophalangeals, wrists, ankles and knees — with morning stiffness, beginning within days of fever onset and persisting for months in a substantial minority.
How do you clinically separate chikungunya from dengue in the same season?
Chikungunya dominates with arthritis, true maculopapular rash, photophobia and near-normal platelets without plasma leakage; dengue dominates with retro-orbital pain, flushing, significant thrombocytopenia, capillary-leak physiology and the day-4-to-7 critical phase.
What is the treatment of chikungunya and the key prescribing caveat?
Supportive — paracetamol, hydration and physiotherapy — with no specific antiviral or licensed vaccine; the caveat is to withhold NSAIDs until dengue is excluded because of bleeding risk in co-epidemic settings.
How long can chikungunya IgM persist and what does that imply?
IgM may persist for months to a year or more after infection, so a positive ELISA in a chronically symptomatic patient could reflect past infection; diagnosis of current illness relies on PCR in week one or rising antibody titres.
What is the concern with chikungunya near delivery?
Vertical transmission during maternal viraemia around delivery can cause severe neonatal chikungunya — fever, rash, oedema, thrombocytopenia and seizures — mandating obstetric-paediatric planning during the Aedes season.