Ross River Virus

Ross River Virus (RRV) Overview

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

Historical Context

• 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

Vectors and Hosts

• 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

Risk Factors

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

Clinical Manifestations

• 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

Acute Symptoms

• 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

Chronic Manifestations

• 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

Diagnosis

• 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

Management

• 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

Prevention

• 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

Public Health Implications

• 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

Summary Points

• Joint pain is the most common symptom.
• Acute symptoms are severe and can last up to 3 months.
• Most symptoms resolve within 4-6 months.
• Comorbid conditions can prolong symptom duration.
• No specific treatment; NSAIDs may provide relief.
• Personal protective measures against mosquitoes are crucial for prevention.