Ross River virus infection A049

Current RMA Instruments

Changes from previous Instruments

ICD Coding

• ICD-9-CM Codes: 066.3
• ICD-10-AM Codes: B33.1

Brief description

Ross River virus is transmitted by mosquitoes and causes a disease manifested by polyarthritis and rash. The illness was first described in northern Australia and subsequently has been observed widely through Australia and many islands of the western South Pacific.

Confirming the diagnosis

Diagnosis can be complex and medical advice may be needed.  Serology results confirming recent infection are required.  There must also be a compatible clinical illness, not just positive serology.  See comments, below.

The relevant medical specialist is an infectious diseases physician.

Additional diagnoses covered by SOP

• Ross river fever
• Symptomatic Ross river virus infection - resolved (see comments)

Conditions not covered by SOP

• Serology indicating past Ross river virus infection – N.I.F. (see comments)
• Asymptomatic Ross river virus infection – N.I.F.
• Post viral fatigue / chronic fatigue syndrome* / other chronic symptomatology > 1 year after initial infection (see comments)
• Barmah forest virus infection^#

* another SOP applies

^# non-SOP condition

Clinical onset

Symptomatic Ross river virus infection usually presents with an acute febrile illness with arthritis and rash.  It may also present with a fever, rash, or arthritis alone.  Some subjects present with a more chronic polyarthritis or polyarthralgia.  Fatigue/lethargy is also a common feature.

The incubation period for acute presentations is usually 3 to 9 days.  Subclinical infection is common.

Clinical worsening

The only SOP worsening factor is for inability to obtain appropriate clinical management.  Treatment consists of supportive care.  No specific antiviral therapy is available.  The condition typically resolves and is not fatal.  

Comments

The SOP applies if there is a clinical illness consistent with the disease and positive serology for recent infection.

Most cases of symptomatic Ross river virus infection resolve within 3 to 6 months.  Persistence of symptoms beyond 12 months is very unusual.  Symptoms after this time are likely to be due to another condition or be unexplained.

A claim for previously symptomatic Ross river virus infection, with contemporary positive serology for recent infection, that has now resolved, can be diagnosed as “Ross river virus infection - resolved” and determined using the SOP.

Serology for Ross river virus infection.

• Definitive diagnosis of recent infection requires two tests, taken approximately 10 to 14 days apart, showing a four-fold rise in IgG titre.
• Serology that is positive for both IgG and IgM is also sufficient to indicate recent infection.
• Positive serology for IgM only, within 7 days of symptom onset, provides a presumptive diagnosis, which should be confirmed by further testing where possible.
• Positive serology for IgG only (negative for IgM) indicates earlier or past infection.

If the only serological evidence available is positive serology for IgG (alone), with testing performed some months after disease onset, the following minimum criteria should be fulfilled before confirming the diagnosis and applying the SOP:

• Characteristic clinical illness
• Onset of symptoms within last 12 months
• Negative tests results for other differential diagnoses (including negative serology for Barmah forest virus)
• Diagnosis supported by treating doctor