Ross River Virus has been in the news lately because of recent outbreaks in Australia where it is endemic. Travelers to Australia, Papua New Guinea, and multiple other Pacific islands may be at risk but most clinicians in the US have never seen a case and don’t know much about Ross River Virus Disease.
So let’s start with a few basics. Ross River Virus is a mosquito-borne alpha virus of the Togaviridae family. It was first isolated in 1963 near the Ross River in Northern Queensland. Kangaroos and wallabies are the primary vertebrate hosts but non-marsupials are now helping to spread the virus. Many different mosquito species of the Aedes (day biters) and Culex (night biters) variety can transmit the virus. About 5000 cases per year are documented in Australia, making it the most common mosquito-borne illness there. There’s no vaccine to prevent infections so round-the-clock insect precautions are warranted. It’s usually present in the tropical coastal areas but can be found inland as well because of the presence of desiccation-resistant mosquito eggs that eventually hatch after a rain. The range is spreading and there’s evidence that climate change is altering the transmission of this virus.
According to CDC, 55-75 % of infected people are asymptomatic. The incubation period is usually 7-9 days but can be up to 21 days. Predominant symptoms include fever, myalgia, arthralgia, polyarthritis and an erythematous maculopapular rash which affects about 50% of patients. The virus invades the synovium and arthritis is quite severe at first. It is usually symmetric, affecting the fingers, wrists, knees, and ankles. Serology most often establishes the diagnosis. Symptoms usually resolve after days to weeks but can last months or years, and can be very debilitating. Treatment is supportive, often consisting primarily of NSAIDS. Interestingly the mechanisms of joint pathology appear to differ among arthritogenic alphaviruses. Methotrexate, useful in chikungunya, has not been shown to be effective in RRVD. Monocytes appear to play a more important role in RVV destructive arthritis and this may help identify better treatments. Other drugs such as digoxin and pentosane polysulfate (PPS) may show more promise but further research is needed.
For further insights, I thought I’d ask one of our travel health colleagues and a local expert, Dr. Mark Newell, a physician at Swinburne University in Melbourne for input:
- Do you have any clinical pearls to share regarding your experience treating patients with this illness?
Surprisingly, in the 18 years I have worked at a student health centre I have not seen a case but am on the lookout for one, especially as there was a big increase in case numbers last year due to heavy rain and flooding in the cooler, more temperate southern states like Victoria where I live and work. The peak transmission season seems to be during the months of January to April
- Do you have any specific advice to share with travelers?
Firstly, I would raise awareness among travelers that the areas of risk may be greater than they imagine. People tend to associate it with travel to the warmer, more northern Australian states (where incidentally dengue fever occurs too) however the cooler, southern areas of Australia all saw big increases in case numbers during 2017. In addition to routine personal protective measures against mosquitos, I would emphasize the following: avoidance of dark-coloured clothing, being extra careful not to get bitten during dawn and dusk and to avoid having potential breeding sites such as potted plants and bird baths too close to a house. As arthralgia is a predominant symptom I would urge them to see a doctor if they develop this, myalgia, or rash when travelling in at-risk areas. And if a traveler is unlucky enough to develop the disease I would advise them that although the musculoskeletal symptoms can last weeks to months, most people recover within a year.
- Centers for Disease Control and Prevention. CDC Health Information for International Travel 2018. New York: Oxford University Press; 2018. Ross River virus disease, accessed Jan 12, 2018.
- Liu X, Tharmarajah K, Taylor A. Ross River virus disease clinical presentation, pathogenesis and current therapeutic strategies. Microbes Infect.2017 Nov;19(11):496-504.
- Lau C, Aubry M, Musso D, Teissier A, Paulous S, Desprès P, de-Lamballerie X, Pastorino B, Cao-Lormeau VM, Weinstein P. New evidence for endemic circulation of Ross River virus in the Pacific Islands and the potential for emergence. Int JInfect Dis. 2017 Apr;57:73-76.
- Andersen LK, Davis MD. Climate change and the epidemiology of selected tick-borne and mosquito-borne diseases: update from the International Society of Dermatology Climate Change Task Force. Int J Dermatol. 2017 Mar;56(3):252-259.
Special thanks to Dr. Newell and to ATHNA Board Member Kevin Long who suggested this topic.
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