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OSAC Health Security Snapshot: Ross River Virus Disease

East Asia & Pacific > Australia; East Asia & Pacific > Fiji; East Asia & Pacific > Kiribati; East Asia & Pacific > Nauru; East Asia & Pacific > Nauru > New Caledonia; East Asia & Pacific > New Zealand; East Asia & Pacific > Palau; East Asia & Pacific > Papua New Guinea; East Asia & Pacific > Samoa; East Asia & Pacific > Solomon Islands; East Asia & Pacific > Tonga; East Asia & Pacific > Tuvalu; East Asia & Pacific > Vanuatu

What is Breaking Out?


Ross River virus disease (RRVD) is spread through mosquito bites. About 55%–75% of people who are infected do not feel sick. For those who do feel sick, symptoms of RRVD include joint (most commonly wrists, knees, ankles, fingers, elbows, shoulders, and jaw) pain and swelling, muscle pain, fever, tiredness, and rash. Joint pain may impact different joints at different times. Most patients recover within a few weeks, but some people experience joint pain, joint stiffness, or tiredness for many months. About 10% of people have ongoing depression and fatigue. Ross River virus disease is not fatal.


Where is it Breaking Out?


Ross River virus infection is the most common mosquito-related infection in Australia. RRVD had been considered a greater risk in rural regions of Australia; however, there have been outbreaks in the suburbs of Brisbane, Sydney, and Perth. In 2015, Brisbane was the epicenter of the largest outbreak of RRV since 1996.


An outbreak in 1979-1980 in South Pacific islands resulted in more than 500,000 cases in American Samoa, Fiji, the Cook Islands, and New Caledonia. Since then, a large-scale RRVD outbreak has not occurred in the region. However, transmission from regional travelers -- most notably from Fiji -- does continue.


Marsupials (e.g. kangaroos, wallabies, opossums) had been thought to be the only other non-human carriers of RRVD, but a newly released study shows that RRVD may have been present in American Samoa after a major outbreak that concluded in 1980—and there are no known wild marsupials there. The study found that non-marsupials (dogs, pigs, cats, bats) can be carriers, possibly explaining a wider RRVD circulation in the South Pacific. Further, the study argues that RRVD could become endemic well beyond its current range.


When Does it Occur?


Disease risk is lower during the colder winter months (June-September in most of the Southern Hemisphere). RRVD is more common after heavy rainfall, high tides, and warm weather that tend to create an environment favorable to mosquito proliferation. According to the Government of South Australia Health Ministry, RRVD in the Northern Territory of Australia is most common from December to March with the highest risk being in January (high tides and rainfall).


Who is Impacted?


Travelers who go to Australia and Papua New Guinea are at risk for RRVD. About 5,000 cases are officially reported in Australia each year, mostly in the northern part of the country. But, it is possible that RRVD is underreported, either because of mild symptoms or misdiagnosis.


Travelers who plan to spend a lot of time outdoors or who will be in areas with a lot of mosquitoes are at increased risk of contracting RRVD.


Why Should I be Concerned?


No vaccine or medicine can prevent RRVD. Patients diagnosed with RRVD and exhibiting symptoms are treated with drugs to minimize inflammation and alleviate joint pain. The public health impact of RRVD is significant. Considering each individual’s (4,179 reported cases in 2007) medical costs, diagnostic costs, and loss of work productivity for just one week, each case of RRV is estimated to be A$1,018-1,180, equating to A$4.3-4.9M borne by Australia alone in 2007.


Current research indicates a potential for RRVD to circulate in a much wider area than those currently recognized. RRVD may have been circulating undetected in several Pacific island countries and territories, possibly misdiagnosed as dengue virus, chikungunya, or Zika virus infections. Diagnosis in many of these areas is difficult, as symptoms are variable and overlap with other conditions, meaning low-level RRV circulation could occur undetected. This could bring RRVD into the realm of an emerging infectious disease, which also has global public health implications. As underscored in the 2016-17 spread of Zika (originally from Africa) from the Pacific to the Americas, the potential for the global spread of a zoonotic disease should not be discounted.


How do I Respond?


The infection is spread by mosquitoes – primarily the genuses Aedes and Culex -- from infected animals to humans. Since the first recorded RRVD case in Australia in 1959, over 40 species of the Aedes and Culex mosquitoes have been identified that can transmit RRV. A key to preventing RRVD is to prevent mosquito bites. Prevention measures can include:

  • using screens in windows,
  • using screens or air curtains in doorways,
  • staying indoors during peak mosquito biting hours,
  • wearing long-sleeved shirts, long pants; and
  • using repellants containing DEET.


It is important that those who are or think they may be infected with RRVD follow these preventative measures as well, because mosquitoes can spread the virus from infected people to other people.


Further, mosquito control programs can also help decrease mosquito populations. This includes emptying any water accumulation and engaging professionals to spray insecticide or larvicide.


Relevant Sources