What this test measures
The scrub typhus rapid test detects IgG and IgM antibodies against Orientia tsutsugamushi, the obligate intracellular bacterium transmitted by the bite of chigger mites. IgM appears 5–7 days after symptom onset and indicates current or recent infection. IgG appears later (10–14 days) and persists for months to years, indicating past exposure.
The rapid card format gives a preliminary answer in 15–30 minutes. Most Indian labs confirm positives with ELISA for IgM (the standard confirmatory test) or PCR during the febrile window.
Why it matters
Scrub typhus is one of the most under-diagnosed causes of acute febrile illness in India — particularly during and after the monsoon (July–November) in agricultural belts, hill stations, and increasingly in urban outskirts of Mumbai, Pune, Delhi, Chennai and the Northeast. Untreated, it can progress within a week to multi-organ dysfunction: acute respiratory distress syndrome (ARDS), acute kidney injury, hepatitis, myocarditis, meningoencephalitis, and shock — with mortality up to 30% in severe untreated cases.
The good news: a single 200 mg dose of doxycycline followed by 7 days of treatment leads to dramatic recovery within 48 hours. Early diagnosis is therefore lifesaving. The classic clinical triad is fever + eschar (a painless black scab at the chigger bite site, often in covered body folds) + regional lymphadenopathy — but the eschar is missed in up to half of Indian patients.
How to prepare
No fasting required. Best taken 5–7 days after fever onset for IgM detection. If sampled too early, the test can be falsely negative; repeat in a week if clinical suspicion remains high. Look carefully for an eschar — it may be in the groin, axilla, behind the ear, or under a bra strap.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Scrub Typhus IgM (—)[1][2] | Negative | — | Positive — current or recent scrub typhus infection (sensitivity rises after day 5). Treat with doxycycline (or azithromycin in children/pregnancy) immediately if clinical suspicion is high. Confirmation by IgM ELISA is recommended. |
| Scrub Typhus IgG (—)[1] | Negative | — | Positive — past infection or exposure. In an acute febrile illness, an isolated IgG positive (without IgM) suggests previous exposure rather than current infection — but if symptoms fit, paired sampling 2 weeks apart (showing a 4-fold rise) can confirm acute disease. |
Scrub typhus tests compared
| Test | Window | Use |
|---|---|---|
| Rapid IgM/IgG card (this test) | Day 5+ | Bedside screen, 15–30 min |
| Scrub typhus IgM ELISA | Day 5–28 | Standard confirmatory test in India |
| Weil-Felix (OX-K agglutination) | Day 7+ | Older test, low sensitivity, still used in some labs |
| Scrub typhus PCR (56-kDa gene) | Day 0–7 (febrile phase) | Best for very early disease |
Frequently asked questions
What is scrub typhus?
An acute febrile illness caused by Orientia tsutsugamushi, transmitted by chigger mite bites. It is one of the most common causes of monsoon-season fever in India and can be fatal if untreated.
Where do you catch scrub typhus?
In rural farms, scrub vegetation, hill stations, and increasingly in urban gardens and parks during monsoon. Chigger mites attach to humans through grass or low vegetation.
What does an eschar look like?
A painless black scab about 5–10 mm wide, sometimes with a red rim, at the site of the chigger bite. It is often in covered, warm body folds — groin, axilla, behind the ear, under a bra strap, around the genitals — and easily missed.
When should this test be taken?
After day 5 of fever. Earlier than that, IgM may not yet be detectable. If clinical suspicion is high, doctors often start doxycycline empirically and test simultaneously.
Is treatment effective?
Highly effective. Doxycycline (or azithromycin) leads to fever resolution within 48 hours in most patients. Mortality of treated disease is under 2%, but rises sharply if treatment is delayed.
How is scrub typhus different from dengue or typhoid?
All three cause monsoon-season fever in India. Scrub typhus typically has an eschar and regional lymph nodes; dengue has low platelets and a positive NS1; typhoid has prolonged fever, abdominal symptoms, and positive blood culture or Widal. Many patients are tested for all three in parallel.
How fast does the report come?
The rapid card test gives a result in 15–30 minutes; most NABL-accredited Mumbai and Thane labs deliver the digital report within 1–2 hours.
Related Infectious Disease tests
Tests commonly ordered alongside SCRUB TYPHUS RAPID TEST (IGG/IGM), or that help interpret an unexpected result.
Sources & references
- ICMR — Scrub Typhus and Rickettsial Diseases Guidelines · accessed 2026-05-30T00:00:00.000Z
- CDC — Scrub Typhus · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Typhus · accessed 2026-05-30T00:00:00.000Z
- Indian Journal of Medical Research — Scrub typhus in India · accessed 2026-05-30T00:00:00.000Z
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