Ross River fever



Last Review Date: December 30, 2018


Overview

Ross River virus disease (Ross River Fever) is a common and important cause of arthritis in Australia and the South Pacific Islands. The virus was first isolated from mosquitoes trapped along the Ross River at Townsville. The infection is acquired through mosquito-bite. It may be acquired in many parts of Australia, but the highest individual risk of infection occurs in the tropical regions of Western Australia, the Northern Territory and Queensland. Most people infected with Ross River virus do not show clinical signs or symptoms and so these infections go unnoticed. Symptomatic infection occurs most commonly in adults from 20 to 50 years of age.

The incubation period (time between the bite by a mosquito carrying the virus and start of symptoms of infection) is 7-9 days on average but may range between 3 and 21 days. The usual symptoms are joint and muscle pain, fever and in some cases a rash, headache and fatigue. The fever may be mild and go unnoticed. The rash involves the chest, back and limbs. The joints of the legs and hands are most often affected and back pain is also relatively common.

At least half of patients with the disease are well enough to return to work within a month of the onset of symptoms and about one in ten may be still suffering with joint pain after three months. The illness tends to subside over time with occasional relapses of joint pain and fatigue. The good news is that the virus does not cause permanent damage to joints and that eventually the symptoms will stop.

Most cases of infections occur in coastal regions which have salt-marsh habitats with large populations of the mosquitoes that can carry the virus but cases are occasionally reported in inland areas of Australia. In northern and central Queensland, Ross River virus is active throughout the year, in other states, disease presence follows spring and summer rains because carrier mosquitoes are more likely to breed under wet conditions.

Ross River virus infection in humans is largely a biological accident as humans are not preferred host for the virus. Common hosts for the virus are wallabies, kangaroos, possums, wombats and occasionally dogs, horses, cattle, pigs and humans.

The symptoms of the disease are similar to those of the Barmah Forest virus disease. The similarities of between the Ross River virus illness and those of the Barmah Forest virus indicate the need to confirm that the correct diagnosis has been made using laboratory tests.


Tests

Suspected cases are confirmed by blood tests measuring two classes of antibodies, IgG and IgM.

Diagnosis can only be regarded as conclusive if you seroconvert for IgG (go from negative IgG test to positive result) or if you have a four-fold rise in IgG antibody titre is detected in two blood samples taken at least two weeks apart, one at the beginning of illness and the second one two to four weeks later.

IgM antibody is a class of antibodies which are often used as indicators of recent infection. However, it is important to remember that in the Ross River disease this class of antibodies may be detected for long periods of time after the infection (18 to 48 months) and false-positive results with some test systems are not uncommon, particularly in individuals with autoimmune disease or who are infected with another agent such as Barmah Forest Virus. When clinically important, it may be useful to have positive IgM antibody results verified by a reference laboratory. Testing for Ross River viral nucleic acid (RNA) can also be performed by reference laboratories but its use is limited to early in the disease course.

Diagnostic laboratories are required by law to report all positive cases to local public health units.


Common questions

  1. What are the symptoms of Ross River virus disease?

    Usual symptoms are joint and muscle pain as well as fever and in some cases rash, headache and fatigue. The fever may be mild and go unnoticed. The rash involves the chest, back and limbs. The joints of legs and hands are most commonly affected and back pain is also relatively common.

    At least half of patients with the disease are well enough to return to work within a month of the onset of symptoms but about one in ten may be still suffering with joint pain after three months. The illness tends to subside over time with occasional relapses of joint pain and fatigue. The good news is that the virus does not cause permanent damage to joints and that eventually the symptoms will stop.

  2. Can recurrent infections occur?

    It is generally considered that infection with Ross River virus results in long-term immunity to the disease. However, two distinct genetic types of virus exist; one predominates in eastern Australia and the other in Western Australia.

  3. Can I pass Ross River virus disease to other people?

    No, this disease is thought to be only passed through the mosquito bite rather than human-to-human contacts, although one case of transfusion transmitted infection was reported recently.

  4. Is there a vaccine for Ross River virus disease?

    No, but researchers are attempting to develop a vaccine.


Prevention and treatment

The most effective way to prevent infection is to protect yourself from mosquito bites while both indoors and outdoors as well as reduce opportunities for mosquito breeding near homes.

There is no specific treatment for Ross River virus infection. Symptoms of joint pain and fever can be treated with painkillers and anti-inflammatory drugs.


Related pages

On this site
Conditions: Barmah Forest virus

Elsewhere on the web
Healthdirect Australia: Ross River virus
Department of Health, Victoria, Infectious Diseases Epidemiology and Surveillance: Ross River and Barmah Forest
NSW Department of Health: Ross River Fact Sheet
University of Sydney and Westmead Hospital, Department of Medical Entomology: Ross River and Barmah Forest


Sources

NOTE: This article is based on research that utilises the sources cited here as well as the collective experience of the Lab Tests Online AU editorial review board. This article is periodically reviewed by the editorial board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
 

Mackenzie JS, Smith DW. Mosquito-borne viruses and epidemic polyarthritis. Med J Aust. 1996;164(2):90-3.

Hills S. Ross River virus and Barmah Forest virus infection. Aust Fam Phys 1996;25:1822-4.

Doggett SL, Russell RC, Clancy J, Haniotis J, Cloonan MJ. Barmah Forest virus epidemic on the South Coast of New South Wales, Australia, 1994-1995: Viruses, vectors, human cases, and environmental factors. J Med Entomol. 1999 Nov;36(6):861-8

Australian arboviruses of medical importance: a handbook for general practitioners and other clinicians. Clement R Boughton. Melbourne: Royal Australian College of General Practitioners Services 1996 (11-16 pp.).

Smith DW, Speers DJ, Mackenzie JS. The viruses of Australia and the risk to tourists. Travel Med Infect Dis 2011 May;9(3):113-25