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Scrub Typhus A009

Last amended 
30 June 2015

In this section

Current RMA Instruments:
Reasonable Hypothesis SOP
72 of 2009
Balance of Probabilities SOP
73 of 2009
Changes from Previous Instruments:

SOP Bulletin 138

ICD Coding:
  • ICD-9-CM Codes: 081.2
  • ICD-10-AM Codes: A75.3

This is a rickettsial infection caused by the bite of a trombiculid mite (a small arachnid), which carries the rickettsia organism.

Is specific diagnostic evidence required to apply the SOP? – No.

But serological evidence of infection by the organism (Orientia tsutsugamushi, previously known as Rickettsia tsutsugamushi) should be obtained if possible.

Are there sub-factors that require specific information? – No.
Additional diagnoses covered by SOP
  • Mite born typhus
  • Tsutsugamushi fever
Conditions excluded from SOP
  • Typhoid (ICD-9 code 002.0; A01.0)
  • Typhus NOS (ICD-9 081.9; ICD-10 A75.9)
  • Louse born typhus (ICD-9 080; ICD-10 A75.0)
  • Murine (flea borne) typhus (ICD-9 081.0; ICD-10 A75.2)
  • Queensland tick typhus (ICD-9 082.3; ICD-10)
  • Tick borne typhus (ICD-9 082; ICD-10 A77)
  • Spotted fever (ICD-9 082.0; ICD-10 A77)
  • Q fever (ICD-9 083.0; ICD-10 A78)
Unconfirmed diagnosis

If, after applying the above information, you are unable to confirm the diagnosis, you should then seek medical officer advice about further investigation.


Fewer than 50% of Westerners develop an eschar (a scab), and fewer than 40% develop a rash (on day 4-6 of illness). The systemic febrile illness has an incubation period of 6-21 days.

North Australia is a location where scrub typhus is known to occur.

A rickettisa is not a bacteria but ‘bacterial like’ organism which has to live within the host cell. The rickettsia classification includes genus of Rickettsia, Orientia, Ehrlichia, Anaplasma, Neorickettsia, and Coxiella.