Arboviruses

Table of Contents
Arboviruses

Research opportunities
Ross River virus
Barmah Forest virus
References

Last Modified 31/10/98

Mosquito transmitted viruses

Mosquito transmitted viruses, in particular Ross River virus (RRV) and Barmah Forest virus (BFV), cause significant morbidity. Ross River virus infection is the most prevalent vector-borne disease in Australia.1 In the Northern Rivers area alone more than 300 infections of RRV and BFV were reported in 1996.

Each of these infections is notifiable by testing laboratories under the Public Health Act 1991.

Research opportunities

The Northern Rivers Institute of Health & Research will be undertaking further research into RRV and BFV over the next 12 months. In particular, the institute will investigate and compare early signs and symptoms, indicators predictive of severity, the longevity of symptoms and the effectiveness of protective practices. The institute is inviting GPs in the Northern Rivers area to assist with recruitment of those potentially infected.

Ross River virus

The incubation period for Ross River virus (RRV) infection varies between three and 21 days, usually seven to nine days.2 Infection is characterised by arthralgia and myalgia, the joints of the extremities most commonly affected. True arthritis occurs in over 40% of those affected. Lethargy, fever and rash are also common. The rash is typically maculopapular and usually involves the trunk or limbs.2 The convalescent period can be prolonged, with significant proportions of those affected reporting arthralgia, myalgia and lethargy several months after onset of symptoms.1, 2

Definitive diagnosis is typically made by serologic testing. Because RRV IgM usually persists for several months, and to rule out a false positive IgM result, convalescent sera should be analysed for IgG.2 The acute phase is that period within seven days of the onset of clinical manifestations and the convalescent phase eight to 28 days post onset.3

Barmah Forest virus

Barmah Forest virus (BFV) has only recently been shown to cause human disease and serological testing has only been generally available since 1994.4 Consequently little is known about the clinical features of Barmah Forest virus infection. Symptoms of BFV appear similar to those of RRV, however arthritis and arthralgia may be less common and less severe, and rash more common and more prominent.2, 4

The incubation period for Barmah Forest is seven to ten days. Diagnostic difficulties are similar to those for RRV.2

Mark Bartletti is a pblic health officer at the Northern Rivers Institute of Health & Research, Lismore, NSW 2480, Australia.

References

1. Westley-Wise V., Beard J., Sladden T., Dunn T. & Simpson J. (1996) Ross River virus infection on the North coast of NSW. Aust NZ J Pub Health. 20(1). pp 87-92.

2. Mackenzie J. & Smith D. (1996) Mosquito-borne viruses and epidemic polyarthritis. MJA. 164. pp90-93.

3. Mackenzie J., Broom A., Calisher C. et al Diagnosis and Reporting of Arboviral infections in Australia. Communicable Diseases Intelligence. 17(10). pp202-206.

4. Beard J., Trent M., Sam G., & Delpech V. (1997) Self-reported morbidity of Barmah Forest virus infection on the north coast of NSW. MJA. 167. pp525-528. GPs interested in participating can contact Mark Bartlett on 02 6620 7526.

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