Ross River Virus

Introduction

Ross River Virus (RRV), also known as Ross River Fever (RRF), is one of the most common viruses in Australia and one that is virtually unknown to most travelers and Australians alike. As of 2004, approximately 4800 cases of Ross River Virus were reported to the Australian Department of Health & Aging. Its clinical name is Epidemic Polyarthritis because of it's long-term rheumatic (arthritic) symptoms. It is classified as an arbovirus - meaning the transmission vectors are a variety of mosquito species (primary) and other insects that feed on blood. Kangaroos and wallabies are the primary mammal hosts for this virus. The first documented outbreak of RRV occurred in New South Wales in 1928 with subsequent outbreaks during World War II in Queensland. RRV was isolated from the Aedes vigilax mosquito in 1959, officially confirmed in 1971 and finally isolated from a polyarthritic patient in 1985. Other outbreaks have been seen in Eastern Indonesia, Papua New Guinea and nearby Pacific Islands over the years.

RRV is a non-fatal disease which mimics the symptoms associated with influenza or rubella (measles) in more severe cases. Recently, RRV infections have been rising in the rural areas Western Australia. RRV can not be transmitted through human to human contact.^[1][2][3]

Prevention

• When outdoors, use insect repellent containing 35% DEET for adults and 10% DEET for children. Follow the directions on the package.
• Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
• Avoid wearing dark coloured clothing.
• Avoid wearing perfume/cologne and scented cosmetics.

Pre-Exposure Vaccines

NO pre or post-exposure vaccines are available.

Symptoms and Treatment

Symptoms

• Statistics have shown that 70-90% of those infected with RRV will not develop any symptoms of the disease during the course of the illness and symptoms in infected children are virtually unseen.

• The remaining 10-30% of infected patients will manifest symptoms that can vary widely. The onset time is 3-21 days with the average symptom onset at 7-9 days.

• Mild symptoms of RRV will mimic those of influenza: lethargy, headache, mild weakness, joint pain, possible low-grade fever (if any), and loss loss of appetite. Recovery occurs in these patients within a few days.

• Moderate symptoms of RRV can mimic those of rubella (measles) and/or varicella (chicken pox): lethargy, headache, joint pain, high fever, loss of appetite, and nausea. A rash developing on the torso and limbs, which may be the first presenting symptom. Because the rash presents itself similarly to those seen with rubella and varicella, it is the main cause of RRV being misdiagnosed. Recovery in these patients can take up to eight weeks though the average recovery time is closer to 14 days in duration.

• Severe symptoms of RRV can be a combination of those seen in moderate manifestations but will also include more localized and intense ligament/tendon/joint pain and swelling of joints (mainly those of the limbs, though the jaw can also be involved). These rheumatic symptoms can present themselves gradually or "explosively". Some patients may experience swelling of the spleen (splenomegaly), spinal chord (meningitis) and/or brain (encephalitis). Some may also develop blood in the urine (haematuria). Recovery time for these patients can take 6-12 months though most recover more quickly with proper diagnosis and treatment.

• RRV can only be accurately diagnosed through laboratory analysis of a patient's blood sample. Additional blood analyses may be performed to rule out other diseases and/or conditions, such as rheumatoid arthritis factor, rubella, varicella, Barmah Forest Virus, and Q fever.

Treatment

At this time there are no specific treatments for RRV. Those requiring medical attention will be treated symptomatically. Those with rheumatic symptoms will be treated with NSAIDS (non-steroidal anti-inflammatory drugs) or other medications designed for rheumatoid-type conditions. ^[1][2][3][4]