Ross River Virus

Australian Family Physician Vol. 38, No. 8, August 2009

Transmission: Mosquito-transmitted alphavirus
Clinical Presentation: Causes epidemic polyarthritis and arthralgias; ~50% of patients also experience fever and rash
Prevalence: Australia’s most common arbovirus with ~5000 cases/year

First Outbreak: 1928 in Narranderra and Hay, New South Wales
Subsequent Outbreaks: WWII troops in Northern Territory and Queensland
Virus Isolation:
- 1959: From Aedes vigilax mosquito near Townsville, Queensland
- 1985: First isolated from an Australian patient with polyarthritis
Geographical Spread: Occurs in all Australian states, including metropolitan areas
Major Outbreaks:
- 1979-1980: Western Pacific outbreak affecting >60,000 people
- Recent reintroduction reported in travelers from Fiji

Primary Vectors: Over 30 mosquito species, including:
- Ae. vigilax
- Ae. camptorhynchus
- Culex annulirostris
- Ae. notoscriptus
Reservoir Hosts: Kangaroos, wallabies, possums, horses, birds, flying foxes
Transmission:
- Human-mosquito-human during epidemics
- Vertical transmission in mosquitoes

Environmental: Higher rainfall and maximum tides, especially in northern Australia (January-April)
Activities: Outdoor activities, particularly camping

Age Group: Most common in adults aged 25-44 years, affecting males and females equally
Incubation Period: 7-9 days (range: 3-21 days)
Subclinical Infection: ~30% of cases

Joint Pain: >95% of patients, commonly symmetrical and acute
- Joints involved: Fingers, toes, wrists, ankles, knees, elbows
- Associated findings: Swelling, effusions, enthesopathy
Other Symptoms:
- Tiredness (>90%)
- Fever, myalgias, headache (50-60%)
- Rash (50%), typically maculopapular on limbs and trunk
- Anorexia, nausea, decreased libido (~33%)
- Rare: Splenomegaly, haematuria, glomerulonephritis, meningitis, encephalitis
Impact: ~50% of patients require time off work

Duration: Symptoms may persist for months, often resolving within 4-6 months
Influence of Comorbid Conditions: Premorbid conditions like rheumatologic issues and depression can prolong recovery
Improvement: Gradual, with NSAID use decreasing over time

Suspected In: Patients with acute polyarthritis/rash and history of travel/residence in endemic areas
Differential Diagnoses: Infectious mononucleosis, rubella, Q fever, rheumatoid arthritis, systemic lupus erythematosus, other arboviruses
Confirmation:
- Serology: Detection of IgM (early infection) and IgG seroconversion (confirmation)
- PCR: Limited use due to short duration of viraemia

No Specific Treatment: Symptomatic relief only
- NSAIDs: Most effective for many patients
- Other: Swimming, hydrotherapy, physiotherapy, massage, rest
- Corticosteroids: Not recommended due to lack of evidence

Personal Protection:
- Screen doors and windows
- Build screened outdoor areas
- Avoid outdoor activities during peak mosquito activity (dawn and dusk)
- Wear long, loose-fitting, light-colored clothing
- Use effective mosquito repellents (DEET or picaridin)
- Use protective clothing and bed nets for babies and young children
Travelling and Camping:
- Screen caravans, tents, and other sleeping equipment
- Avoid areas with high mosquito activity
Eliminate Breeding Habitats:
- Dispose of water-holding containers
- Stock ornamental ponds with mosquito-eating fish
- Maintain swimming pools
- Drain ground depressions holding water
- Fit mosquito-proof covers to septic systems
- Screen rainwater tanks
- Empty pot plant drip trays weekly
- Clean animal and pet drinking bowls weekly
- Empty water-holding plants weekly
- Use residual chemical sprays as needed

Notification: Required to state/territory health departments
Outbreak Control: Focus on mosquito species identification and breeding site elimination
Environmental Factors: Rainy periods, flooding, urban development in wetland areas, climate variability