Brisbane, Australia is currently the epicenter of the largest outbreak of Ross River Virus the country has experienced since 1996 . As of March 14th, there have been 2,835 cases since January 1, 2015 . This is approximately 500 more cases than were seen in the previous year .
About Ross River Virus
This vector-borne disease is primarily found in Australia, Papua New Guinea, parts of Indonesia, and the western Pacific Islands . Ross River Virus (RRV) is spread indirectly, through the bite of an infected mosquito. This means that the virus cannot be spread through person-to-person contact. Animals such as wallabies and possums are the natural reservoir for the virus . When a mosquito bites an infected animal, it becomes a vector and is capable of passing the virus to humans through an infectious bite [1,2]. The incubation period for RRV is 7 to 14 days, and common symptoms include swollen joints (primarily the ankles, fingers, knees, and wrists) and muscles. Other symptoms include fever, fatigue, headache, swollen glands, as well as rash .
Currently, there is no medical cure for Ross River Virus . Patients are treated with drugs to minimize inflammation and alleviate joint pain .
Rainfall & Mosquitoes
Heavy rainfall and high tides over the recent Australian summer have created the perfect environment for mosquito proliferation throughout Queensland . The situation was exacerbated when Tropical Cyclone Marcia hit Queensland on February 20, 2015, resulting in widespread flooding [2,3]. These environmental factors contributed to an increased prevalence of mosquitoes, which led to an increased number of individuals being bitten by infected mosquitoes, ultimately resulting in this large outbreak of RRV. A major mosquito control program has been implemented by the Brisbane City Council to decrease the vector population in hopes of controlling the outbreak .
Australia is host to an assortment of mosquito breeds capable of spreading RRV . To further complicate matters, each of these mosquito species has a preferred breeding habitat, making targeted vector control difficult. For example, the Aedes vigilax mosquito prefers to breed in salt marshes, while the Aedes normanensis mosquito proliferates in floodwater, and the Aedes notoscriptus is commonly found in backyards .
Because there is no vaccine for RRV, prevention typically focuses on limiting contact with the disease’s vector – mosquitoes. This includes adding screens to your house and staying indoors during peak mosquito biting hours. If you are outdoors around sunrise or sunset, be sure to wear long-sleeved shirts, long pants, and use repellants containing DEET [1,2]. Reducing mosquito habitats and breeding sites is another important preventive measure. Any pool of water, including household items such as empty containers and flowerpots, can serve as a mosquito breeding ground.
There are also seasonal fluctuations related to the spread of RRV. Water availability and temperature greatly impact mosquito prevalence. For instance, humid weather allows the mosquito to live longer allowing it to become infectious, breed, and infect a human. In the Northern Territory of Australia, for example, the main risk season is from December to March . The highest risk is in January, when high tides and increased rainfall result in an increase of mosquitoes .
To address the outbreak in Australia, health authorities in Queensland recommend that residents clean out their gutters to limit stagnant water, as well as other mosquito breeding ground on their property . Additionally, they have recommended that individuals add protective screens to their windows and doors, use repellents and sleep under insecticide treated nets .