Mosquitoes can transmit many harmful diseases to humans. Ross River virus, for example, is a mosquito-borne disease that was first discovered in Australia in the 1960s. Most people who contract Ross River virus don’t get ill, but some individuals experience symptoms that last for weeks or months after infection.
Read on to learn about this virus, its symptoms, and ways to prevent infection.
What Is Ross River Virus?
Ross River virus is a vector-borne disease that primarily affects people in Australia, Papua New Guinea, and certain South Pacific islands, including the Cook Islands, Fiji, New Caledonia, and Samoa.
An estimated 5,000 Australians contract Ross River virus each year, with treatment costing approximately $2.8 to 5.7 million Australian dollars annually. Expenses related to the virus include patients taking time off work to recover, physician visits, and testing costs.
Ross River virus is an alphavirus in the Togaviridae family. This family also includes chikungunya and Mayaro viruses. Common characteristics of alphaviruses include:
- Single-stranded ribonucleic acid
- Transmission by arthropods like mosquitos
- Symptoms that can last months or years
Several significant outbreaks of Ross River virus occurred in the last decade. From late 2014 to 2015, an outbreak of approximately 9,500 cases occurred in Queensland, Australia. Then, in 2017, almost 7,000 people contracted the virus in New South Wales, Victoria, and Western Australia.
How Does Ross River Virus Spread?
Researchers have found at least three species of mosquitoes that likely serve as vectors, or transmitters, of Ross River virus. These mosquitoes spread the virus through two methods:
Animal-mosquito-human transmission. First, mosquitoes can carry the virus from infected nonhuman vertebrates to humans. Animals like dogs, kangaroos, rodents, and wallabies serve as hosts for the Ross River virus. A mosquito bites the infected animal and then bites a human, passing on the disease.
Human-mosquito-human transmission. Research also suggests that mosquitoes can spread Ross River virus through human-mosquito-human transmission. This method of transmission was linked to significant outbreaks in the Cook Islands in 1979 and 1980.
What Are the Symptoms of Ross River Virus?
Many people who contract Ross River virus don’t realize they have been infected. An estimated 55 to 75% of cases of the virus are asymptomatic.
Other individuals, though, experience both acute (short-term) and chronic (long-term) symptoms. Symptoms typically appear within 7 to 9 days of infection. However, you may notice signs as early as 3 days or as late as 21 days after being bitten by an infected mosquito.
Common acute Ross River virus symptoms include:
- Pain in the ankles, elbows, knees, and other joints (reported by over 95% of patients)
- Fatigue (90% of patients)
- Fever (50 to 60% of patients)
- Headache (50 to 60% of patients)
- Joint swelling (50% of patients)
- Rashes on the limbs and torso (50% of patients)
Less common acute symptoms include:
- Effusions
- Enthesopathy (inflammation of the tendons)
- Anorexia
- Nausea
- Decreased libido
- Splenomegaly (enlarged spleen)
- Meningitis
- Encephalitis (inflammation of the brain tissue)
Acute symptoms usually resolve after several weeks. However, some patients suffer from long-term complications lasting for six months or longer. The long-term effects of Ross River virus include joint pain and fatigue.
To date, Ross River virus has caused no documented human deaths.
How Is Ross River Virus Diagnosed?
A healthcare provider can diagnose Ross River virus through paired serology, a technique that involves two blood tests taken two weeks apart. The test detects antibodies that your body creates to fight the virus.
Ross River virus blood tests can diagnose many cases but are not 100% reliable. An estimated 3% of tests give false positives, and 6% give false negatives. If you believe you have received an inaccurate test result, you should consult your healthcare provider.
Can Ross River Virus Be Cured?
Most people infected by Ross River virus recover completely after several months. This virus doesn’t respond to antibiotics, so Ross River virus treatment focuses on relieving patients’ symptoms. Attempts to treat Ross River virus with corticosteroids have also been ineffective, and researchers don’t recommend using these medications.
On the other hand, healthcare providers can prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) to help treat symptoms like headaches and joint pain. Patients may also experience symptom relief following hydrotherapy, massages, swimming, and other physical interventions.
What Factors Impact Ross River Virus Cases?
Most cases of Ross River virus occur in the tropical regions of Australia, such as the Northern Territory, Queensland, and Western Australia. The disease spreads more easily during the wet season, which spans from February to May. Heavy rainfall and humidity occur during this period, increasing the amount of still water collected in puddles and containers. Mosquitoes breed and lay eggs in these environments, increasing the risk of infection.
Other factors that help spread Ross River virus include:
- Flooding
- Urban development in salt marshes and wetlands
How Can You Prevent Ross River Virus From Affecting Your Health?
You can lower your risks of contracting Ross River virus by taking preventative measures while traveling in Australia and other regions where the disease is endemic. Many people get infected while engaging in outdoor activities like camping and kayaking, so you should exercise particular care during the rainy season or periods of flooding.
Effective strategies to prevent Ross River virus include:
- Applying 0.5% permethrin, an insecticide, to your clothing and hiking gear to repel mosquitos. Avoid applying permethrin directly on your skin.
- Placing a permethrin-treated mosquito net over your sleeping area to stop mosquitos from biting you at night.
- Keeping windows closed if they do not have screens to reduce the number of mosquitos entering the space.
- Using an insect repellant approved by the Environmental Protection Agency. Look for a repellant that contains DEET, IR3535, picaridin, oil of lemon eucalyptus, or para-menthane-diol.
- Wear long-sleeved shirts and pants that will protect your skin from mosquito bites.
These preventative measures can help protect you from Ross River virus, allowing you to enjoy your travels without worry.